A 1 1 1 4 2 2 4 2 A OFFICIAL USE ONLY

NBS

PUBLICATIONS

NBSIR 78-1510

Intruder Detection Using Trace

Constituent Analysis

J. R. DeVoe

D. M. Sweger

R. A. Velapoldi

Center for Analytical Chemistry

National Bureau of Standards

Prepared by

Law Enforcement Standards Laboratory

Center for Consumer Product Technology

National Bureau of Standards

Washington, D.C. 20234

May 1979

Progress Report

Prepared for Nuclear Surety Directorate

Defense Nuclear Agency

Mngton, D.C- 20305

vQQhmhhi

ork was sponsored by the Defense Nuclear Agency under

100 k Code PQ99QAX DE910 and Work Unit Code 31

. U56

78-1510

C z OFFICIAL USE ONLY

OFFICIAL USE ONLY

NBSIR 78-1510

INTRUDER DETECTION USING TRACE

CONSTITUENT ANALYSIS

:?p 2 s „

H S u>

£. x

J. R. DeVoe

D. M. Sweger

R. A. Velapoldi

Center for Analytical Chemistry

National Bureau of Standards

Prepared by

Law Enforcement Standards Laboratory

Center for Consumer Product Technology

National Bureau of Standards

Washington, D.C. 20234

May 1979

Progress Report

Prepared for Nuclear Surety Directorate

Defense Nuclear Agency

Washington, D.C. 20305

This work was sponsored by the Defense Nuclear Agency under

Subtask Code PQ99QAX DE910 and Work Unit Code 31

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
• * . .

v, .

»* i
OFFICIAL USE ONLY

ACKNOWLEDGMENTS

This document was prepared by the Law Enforcement Standards

Laboratory of the National Bureau of Standards under the

direction of Lawrence K. EXiason, Manager, Security Systems

Program, and Jacob J. Diamond, Chief of LESL.

ii

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!

.

• *

•
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Foreword

The Defense Nuclear Agency (DMA) is engaged in a continuing

effort to enhance the security of nuclear weapons storage. In

this effort, it is receiving technical support from the

National Bureau of Standards' Law Enforcement Standards

Laboratory (LESL) , whose overall program involves the

application of science and technology to the problems of crime

prevention, law enforcement and criminal justice.

LESL is supporting DNA's physical security program in the

behavioral science, the chemical science and the ballistic

materials areas, among others.

Among the tasks being performed by LESL for DMA are the

preparation and publication of several series of technical

reports on the results of its researches. This document is one

such report.

Technical comments and suggestions are invited from all

interested parties. They may be addressed to the authors or to

the Law Enforcement Standards Laboratory, National Bureau of

Standards, Washington, D.C. 20234.

Jacob J. Diamond

Chief, Law Enforcement Standards

Laboratory

iii

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Contents

I. Introduction . . .

II. Particle Luminescence

Phase 1. Characterization of Candidate

Particles . . Phase 2. Types of Uniquely Tagged Particles . Phase 3. Methods of Deployment . Phase 4. Evaluation of the Sensitivity . . . Countermeasures . . .

III. Infrared Lasers for Trace Gas Analysis . . . . Phase 1. Establish Limits of Detection and

Feasibility for Isotopic Ratio

Measurements

Formaldehyde

Laser Ranging Chemical Analysis

IV. The Olfactory Receptor as an Analytical

Instrument . References

Appendix A- -Assignment of Vibration-Rotation Energy

Levels in Formaldehyde . .

Page

1

2

3

22

22

23

24

25

27

30

30

36

41

43

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I . INTRODUCTION

This research project is based on the following scenario

for an intruder deterrent and detection system. The basic

assumption is that an intruder has entered a secured space and

has thereby set off an alarm that alerts guards and triggers

mechanisms which release and disperse one or more chemical

substances. The functions of the chemicals are to: (1) Act as

an immediate deterrent by producing low visibility and/or a noxious atmosphere causing choking, nausea, etc., and (2) to

adhere to the intruder so that he can be traced and

unequivocally identified if he escapes.

The intruder detection system envisions the use of two

distinct chemical analyzers. The first is an on-site chemical

gas analyzer that has moderate sensitivity and quick response

(e.g., seconds) , and is either portable or able to quickly scan

a large area. This chemical analyzer should provide clues to

the direction of the intruder's flight.

The second is an off-site chemical analyzer that can be

used to detect the chemical on the intruder ' s person or in

space that he has occupied. This analyzer should have the

highest possible sensitivity and should be able to identify the

taggant chemical uniquely, with few or no false positives. It

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would be desirable if this instrument were portable or at least

semi-portable (e.g. , in a small truck or van)

.

The remainder of this report discusses three chemical

analysis techniques that should be suitable [8].*

II. PARTICLE LUMINESCENCE

Particles containing a luminescent material can be

incorporated into a spray system which, when triggered by an

intruder, would disperse the particles throughout a room. If

the intruder manages to escape from the secured space, a trail

of particles should be observable with appropriate detection

equipment. This technique is similar to that recently

demonstrated for the tagging of explosives [1]. The particles

can be fabricated in such a way that unique identification is

possible. This is accomplished by adding known mixtures of

luminescent substances to various glass formulations and then

converting them to glass microspheres. The luminescent spectra

of these particles, coupled with their sphericity, uniquely

identify them.

The purpose of this project is to explore the possibility

of fabricating such particles and to suggest possible methods

for their use. There are five phases to this project.

1. Characterization of candidate particles.

2. Exploration of the extent of unique types of tagged

particles

.

*Numbers in brackets refer to the references on page 41.

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3. Experimentation with various methods of deployment.

4. Evaluation of the sensitivity of the tagging

system.

5. Evaluation of the effectiveness of the system

by means of field tests.

Phase 1. Characterization of Candidate Particles

The luminenscence spectra of the glass microspheres were

measured with the microspectrof luorimeter depicted in figure 1.

Excitation radiation, produced by a xenon or mercury arc

source, passes through a BG 38 red-suppression filter

(transmitting radiation from 325 to 700 nm) , and through a Ploem illuminator (dichroic mirror-barrier filter combination)

to the sample. Three Ploem combinations were used: 1-1, which

provided excitation over the range 325-400 nm ( Vax'^® nm) ; 2-

2, which provides excitation from 350-450 nm (^max~400 hTM)

and

3-3, which provided excitation from 375 to 500 nm (^max~450

nm) . In general the 1-1 or 2-2 combinations were used for

sample excitation, since the barrier filter in the 3-3

combination distorts the emission spectrum below a wavelength

of about 580 nm. The radiation emitted by the luminophor in

the particle proceeds back through the dichroic mirror, the

barrier filter, a measuring aperture and a 0.1 m grating

monochromator, and is measured by a photomultiplier tube (S-20

response) . The signal is amplified and the spectrum is

recorded directly on an X-Y recorder.

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PHOTOMULTIPLIER TUBE

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E

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Figure 1. Block diagram of apparatus used for the determination of the

luminance emission spectrum.

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The microparticles used were glass beads containing a

mixture of two rare earth and/or transition metal ion

luminophors. The two ions selected for a particular melt had

emission spectra in the green and the orange or red portions of

the visible spectrum, respectively. The green luminophors

included the terbium, copper, dysprosium, and uranyl ions while

the orange and red luminophors were the samarium and europium

ions, respectively [2] . The emission spectrum of each

luminophor and the ratios of selected emission peaks of the two

luminophors made it possible to identify uniquely the particle

and its composition.

Several preliminary glass melts were made [3]

,

with the

compositions shown in the first seven columns of table 1; each

of these contained two luminophores . Four additional glasses

were made, each of which contained a single luninophore. Small

portions of each of these melts were crushed and their spectra

measured with the microspectrof luorimeter

The spectra of the individual uranyl, europium, terbium,

and samarium ions in glass are given in figures 2 and 3. The

spectra of combinations of these and other inorganic ions are

given in figures 4-12 and the instrumental conditions under

which the spectra were recorded are summarized in table 2. Of

the seven preliminary melts with two luminophores only sample

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Table

1.

Compositions

of

the

preliminary

glass

melts.

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Table

2.

Instrumental

parameters

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emission

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sample

glass

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K~1032 f containing a mixture of Sm^ + and Tb^ +

, gave emission

peaks due to the individual ions that were of comparable

intensities. The emission spectra of sample K-1032 using two

Ploem combinations (1-1 and 2-2) for excitation and two

monochromator slit widths (0.5 and 2.0 mm, corresponding to

bandpasses of 4.25 and 17 nn, respectively), are shown in

figures 5, 6 and 7. These figures show that using a 1-1 Ploem

combination for excitation results in emission spectra in which

the peaks attributable to both ions can be readily identified.

On the other hand, use of the 2-2 Ploem excitation combination

(figs. 5 and 6) results in emission spectra attributable only

to the Sm^ + ion (i.e., selective excitation).

Although the use of 0.5 ram slits produces peaks with better

spectral resolution, from which the identification of

individual rare earth ion emission peaks can more easily be

made (fig. 7), the sharpness of these peaks makes peak height

measurement more difficult. The use of 2 mm slits, on the

other hand, makes it easier to measure the peak heights and

facilitates the determination of the relative ratios of the Tb^ +

peak at ^544 nm and the Sm3+ peak at vG02 nm. The concomitant

decrease in resolution does not hinder particle identification.

In all the other preliminary glass melts (samples K-1031,

K-1045, K-1064, K-1077, K-1078 and K-1079) , there appears to be

11

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either luminescent quenching or extensive energy transfer from

the green (Dy3 +

, Cu2+

, Tb3+, UC>2

2+

) or orange (Sm3+

) emitting

moiety to the red (Eu3+ ) emitting moiety. In figure 4, the

peaks due to Tb3+ emission can be identified at % 475 and 545

nm, but the intensities are much lower than would be expected

if no quenching or energy transfer mechanisms were operating.

Similarly, in figures 8-12/ the samples exhibit emission

spectra due mainly to the Eu3 + ion. In figure 8, a small peak

at ^530 nm may be due to copper emission (A =535-540 nn in

glasses); however, this oeak is also visible in figure 11,

which gives the emission spectra of a sample containing only Eu

and Dy^

+

. Thus, this peak is probably due to very weak

3+ emissions from the second excited level of Eu , i.e.,

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or 12, they would certainly be masked by the intense emissions

3+ 3 + uue to Eu . A small peak due to the emission from the Dy

species is present at 481 nm (fig. 11) ; however, it also is too

3+ low to be useful. The Dy peak at 575 nn is completely masked

3+ by the Eu emission.

15

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In summary, one melt, K-1032, containing Tb3+ and Sm3+ in

concentrations of 1,0 mole percent each as the oxides, gives

peaks of comparable intensities attributable to the individual

ions when excited with radiation passed by a Ploem dichroic

mirror-barrier filter combination designated 1-1.

Two additional preliminary melts, designated xxx and yyy in

table 1, will be made. Emission spectra will be measured for

these materials. Excitation spectra for all melts will be made

on the NBS reference spectroradiometer to determine whether an

excitation wavelength region can be found which will excite

both ions with the resulting emission coming from the

individual ions rather than having the energy transfer process

occur with consequent strong emission from only one of the

ions

A decision will then be made as to which glass will be used

in the final testing. If a decision were to be made at this

time, melt K-103 2 containing Sm3+ and Tb3+ would be selected

for further work. Using this system as a model, the following

work will be done: 1) prepare several melts of varying Sm3+

and Tb3+ concentration; 2) measure emission spectra; 3)

calculate the Tb3+ (^544 nr:) /Sm3+ (^602 ma) peak ratios; and *

)

obtain precision and accuracy data to determine the smallest

ratio difference that could be determined. The particles in

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these tests would be in the 30-70 pm diameter range, and

modification of the detection system to incorporate photon

counting may be necessary.

Phase 2. Types of Uniquely Tagged Part ic les

It is presumed that one might wish to uniquely identify

each of a substantial number of secured spaces and, therefore,

it would be useful to know to what extent this could be

accomplished by the tagged particle technique. There are a number of possible ways to engender unique particulate tags.

The simplest is to mix two or more particle types together in

known ratios. Among other possibilities are the following:

o produce single particles with varying ratios of components.

o coat the particles with unique fluorescent substances.

o transform the particle shapes from microspheres to

aggregates of two, three, four or more microspheres

.

o change the sizes of the microspheres.

There are undoubtedly other possibilities that can be

considered, but this project will address only mixtures of

components in a single glass microsphere and mixtures of •

microspheres each of which contain a single component.

Phase 3. Methods of D eplovmen t

A mass of beads with diameters of tens of micrometers pours

like a liquid, and can easily be dispersed as a smoke. Such

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small particles will adhere to most nonconductive surfaces by

electrostatic attraction, but larger particles might not. It

might thus be desirable to aspirate them in a "sticky" fluid so

that particles of all sizes would adhere to all surfaces [4].

On the other hand, it is important that once attached, the

particles should be moderately easy to remove from the surface

for two reasons. First, so that the intruder would leave a

trail of particulate matter and, secondly, to facilitate

decontamination of the guarded space.

Phase 4. Evaluation of the Sens itivity

This ultimate test of the method will be performed for both

mixed single-component particles and mixed-component particles.

Tests will be made to determine sensitivity to dilution with a known inert particulate material (e.g., polyethylene spheres)

and with ordinary dirt. Studies will be made of the

statistical technique to be used for searching a collected

sample for the unique particles by means of a microscope. From

this study one should be able to predict the dilution factor

that can be tolerated before detectability is lost. Field

tests will be performed at Crane, Indiana [5]. Certain simple

tests such as the purposeful addition of particles to shoes and

clothing will be made to obtain some feeling for practical

sensitivity and the length of time during which one might hope

to detect the presence of the unique particles.

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Countermeasures

Intruders who have set off a Forced Entry Deterrent System

(FEDS) will presumably knov; that everything in sight has been

coated with one or more chemicals. They will therefore try to

clean themselves and the stolen object as soon as possible. If

this is done thoroughly, using the latest clean room

technology, there is good likelihood that the trail will end at

that point. Evidence will be left in their decontamination

chamber for some time (probably v/eeks) unless the

decontamination room itself is decontaminated.

The stolen object should therefore be tagged covertly

(e.g., with paint or oil containing the particles), and could

even be designed to leave a particulate trail even after

rigorous decontamination of the surface. This should produce a successful countermeasure to decontamination. Furthermore, the

intruders cannot check the efficiency of their decontamination

unless they can match the ultra-high sensitivity of the

detection system that is used at NBS [6]

.

The vehicle used to transport the device will be

irreversibly contaminated. Cross contamination by objects

contacted by the intruder is very likely. The driver of the

vehicle used to move the stolen object away from the area is

also likely to be contaminated. In summary, one might liken

O

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the process to contamination with an influenza virus. Once it

is released , it is very likely to propagate by a number of

unforeseen pathways. The only difference is that the virus

propagates itself by multiplication [7].

III. INFRARED LASERS FOR TRACE GAS ANALYSIS

The purpose of this project is to investigate the use of

lasers for trace gas analysis. It is postulated that a

chemical is incorporated into a FEDS and is released either

separately or together with the particulate tags described in

the previous section, covering the secured space and the

intruder when the release mechanism is activated. The material

slowly releases a given amount of gaseous substance that is

then detected by means of the laser radiation.

Detection of the escaped intruder requires the very high

sensitivity and selectivity of the laser gas analysis technique.

High selectivity is based upon the fact that the taggant gas is

made from elements with uniquely defined isotopic ratios;

consequently there is little likelihood of finding an identical

gas in the environment. This means that the gas analysis

system must be able to measure isotopic ratios, e.g., of carbon

or oxygen if carbon monoxide or formaldehyde were to be used.

Only the gas chromatograph-mass spectrometer (GC-MS) system and

25

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the infrarea laser seem to have both sufficiently low detection

limits and isotope selectivity. The GC-MS is a very slow

analysis method compared to the laser spectrophotometric

technique. Another interesting potential application of the

infrared laser is its use for long path length analysis (to be

described in a subsequent section) . For these reasons the

laser spectroscopic analysis was considered to be the most

likely technique for accommodating all of the requirements for

this analysis.

Two infrared laser systems have been selected for study: the

Stark-modulated C0

2 gas laser system and the semiconductor

diode laser system. During phase 1 of this project each system

will be evaluated with respect to its performance in fulfilling

two requirements of the gas analysis technique: 1) Capability

to measure isotopic ratios in simple molecules and 2) adequate

limit of detection.

Phase 2 involves performing tests that establish the

retention times of various gases absorbed on clothing and skin.

Phase 3 will establish the feasibility of the technique under

simulated field conditions.

The initial selection of candidate gases will be based upon

the results obtained in phase 1 of the project. however, it is

suspected that the data obtained in phases 2 and 3 may result

26

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in the selection being based on an iterative process among all

three phases of the project.

Phase 1. Establish Limits of Detection and Feas ibility

of I sotopic Ra tio Measurements

Little quantitative work has been published on the

measurement of isotope ratios by infrared spectrophotometry, so

initial studies have been centered on establsihing the

capability. Measurements of the naturally-occurring isotope

ratios of 12 C/ 13C in methyl fluoride were made to about 1

percent relative standard deviation with the Stark-modulated CO2

laser system. Other gases that have been investigated are

carbonyl sulfide, formaldehyde , carbon monoxide and methyl

mercaptan. While some of these gases meet a few of the tagging

system criteria, none meet all of them. Consequently other

gases are being considered, including ethyl mercaptan, some of

the alkyl disulfides and acetonitrile.

A very important consideration in optimizing the isotopic

ratio measurements is the classification of the important

segments of the infrared spectrum with respect to mode of

vibration and rotation. These assignments can help to

determine the energy level that is most intense for each

isotope. This could be done by time consuming sweeping of the

spectrum experimentally, but among the thousands of lines it

27

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would be easy to miss an important region of the spectrum

without at least a superficial evaluation of the gas molecule's

structure and its effect on the infrared spectrum.

It is very difficult to achieve positive verification of

the wavelength of the laser within the resolution of a single

peak (0.005 cm“^) in the infrared spectrum. This means that

the experiments must identify a set of peaks as being

associated with an assigned set of energy levels identified

with a structural property within the molecule, just to be

assured that the same peak is being measured each time. This

mandates theoretical studies involving line assignments.

Techniques have been developed for simple molecules and an

example of an approach for the formaldehyde molecule is

presented in appendix A.

Laser spectroscopy is rapidly becoming the chemical

analysis technique with the lowest detection limits [9,10].

Measurements of the limit of detection have proceeded in the

direction of establishing background elimination procedures and

in the reduction of noise in the system. For the purposes of

this study, detection limits will become quantitation limits

because sufficient concentration of gas will be needed to

measure the isotopic ratio. Phases 2 and 3 have not been

28

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initiated but if phase 1 is successful they are planned to be

completed in two more years.

In general the operation of the laser is straightforward

and uncomplicated. The electronics are sufficiently well

designed, with interlocks that prevent operation at too high a current or temperature. As a result, it is virtually

impossible to make an error that damages the laser.

Temperature control is stable and easy to achieve, and changing

temperatures for tuning purposes is rapid and reproducible.

These features make the use of the laser routine.

The tuning characteristics are similar to those described

in the literature. That is, as one changes the current at a

given temperature, the laser will tune continuously and then

jump to another wavelength in a discontinuous fashion. It

should be noted, however, that the laser will always operate in

the same frequency regions and skip over the same regions, no

matter what the temperature. For example, if the laser tunes

over 1700-1703 crn“^ and skips to 1705-1708 cm” ^ a particular

temperature, skipping over 1703-1705 cm”^ , the laser will tune

essentially the same way at other operating temperatures and

skip over the same regions. Thus, there are "holes" in the

tuning curve that cannot be reached with that diode; however,

another diode could be fabricated to cover the skipped areas.

29

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Reproducibility in day-to-day operation was found to be quite

good. That is, returning to the same temperature setting at

the same laser current gives the same frequency output.

Formaldehyde

Several spectra of formaldehyde were taken at low

pressures. The cell was evacuated and filled to a pressure of

10-20 millitorr with formaldehyde that was obtained by heating

paraformaldehyde. The spectra of both the cells and the etalon

(interference filter) were taken on successive sweeps under

identical laser conditions and recorded together. A typical

spectrum is shown in figure 13.

For accurate analysis of the spectra it was considered to

be desirable to calibrate the etalon independently of the

calibration supplied by the manufacturer. To this end, the

etalon was removed from the instrument (although kept in its

mount) and its length measured. The length was determined to

be 2.59011 + .00025 cm @ 19.8°C, quite close to the 2.5905

cm specified by the manufacturer. Moreover, the flatness was

found to be within about 2 x 10

-

^ cm.

Laser Ranging Chemica1 Analys is

Long-pathlength atmospheric analysis can be conveniently

performed with inexpensive, reliable lasers. This

30

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u

njm

r-H

<u T3O

0)u

3

tr> •H

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1775.00

1774.50

1774.00

FBEOMEiCY

(WAVENUMBERS)
OFFICIAL USE ONLY

spectrophotometric analysis method uses reflectors that return

the beam to a detector located near the laser. This system

impacts upon the intruder detection problem in two ways.

First, a network of laser beams can be used to cross a secured

space. Any object that breaks a beam would trigger an alarm.

Second, the same beam can be analyzed for the absorption

spectra of the gaseous components in the air within the secured

space

.

Intruder detection by the beam-break approach is a classic

one and much study has been devoted to this type of system by

others. As far as is known, however, no one has used the same

laser beam for chemical analysis of the atmosphere in the

secured space. There are two reasons for doing this: one is

an immediate verification that a FEDS had been triggered, and

the other is that the existence of poisonous gases can be

detected in the event that the intruder attempts to neutralize

the guards by introducing them into the atmosphere in the

region of the secured space. Such a system might also detect

the presence of gases that are damaging to electronic

components by determining the composition of exhaust air from

the various buildings.

If one assumes that the secure area is about 1 km , it

should be possible to detect constituents in the atmosphere at

32

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the 100 parts per billion level. The ability to uniquely

identify particular constituents in the atmosphere will be

impaired as a result of nitrogen (in air) collisional

broadening of the infrared molecular transitions. While

isotopic ratio analysis could not be performed, the system

could transmit an alarm whenever the composition of the

atmosphere changed significantly. That is, when certain

frequencies that are not characteristic of the normal ambient

atmosphere were absorbed, an alarm would sound and further

investigation could be made.

Currently, we are thinking about a CO2 gas laser which

emits at some eighty different discrete frequencies. Special

optics can be configured to split the laser into a series of

beams that would cover the secured space (fig. 14) . Reflectors

would be situated around the periphery of the secured space,

and the returned beam would compare the absorption per unit

radiance of the incident laser beam for each of the eighty

laser frequencies (fig. 15).

All of this technology is currently available and a prototype could be fabricated in the single beam mode to

determine its potential. The gas lasers are commercially

available and are known to be very stable with long continuous

33

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USE ONLY

!

S'

34

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rigure

14.

Schematic

diagram

of

laser

beam

umbrella.
Reflecting

Surface

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roc

O)

c/5

<Dw

(0

CM o

o

o

4)

<D Q

D)c

m w

c «

U) o>o

V) o

CL

OFFICIAL USE ONLY

Figure

15.

Schematic

diagram

of

laser

absorptiometric

detection

system.
OFFICIAL USE ONLY

operating times at sufficient power. The detector systems are

relatively low in cost.

One might obtain data as shown in figure 16. Each of the

bars on the graph represent the laser beam intensity returned

for a given frequency (designated as R(26), R(24), P(12),

etc.). The upper segments of the bars indicate the increases

in absorption as a consequence of the introduction of two

foreign gases (at concentrations of 1 ppm each) into a normal

atmosphere. The absorption characteristics of the two

contaminating gases, as well as those of the normal atmosphere,

are markedly different at various frequencies. Therefore, one

treats the data as a linear combination of uncorrelated

components and, by using appropriate computations, can

determine an unusual component in the atmosphere. These

computations involve pattern recognition techniques which have

become quite sophisticated in their ability to distinguish

small effects in a complex milieu of other effects.

IV. THE OLFACTORY RECEPTOR AS AN ANALYTICAL INSTRUMENT

We are all aware of the ability of many animals (e.g..,

bloodhounds) to detect the scent of an escaped prisoner

sometimes tens of hours after the trail has been created.

Moreover, the scent is uniquely identified with the escaped

36

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OFFICIAL USE

o

rjp

O £ U O P-, 3 C

<L) rO X rH P U)C TJ p 0 c O-H Ifl P

P 3 0)

<D X) G

-G -H (D £ P rH 3 -U c c x

o P

<c u OJ M 0) £

0 > G.

4-' -H G

-P m to .-I C rH O Cl 01

•rH P 3

-P rH O tn G

<D C

U3 -H r-, 5 'O

tn O rH w x •— 0 w

P 0) O - P

</) <D • c <D x: r^ 0 C D-. on

•rH "H m I—

UH 0“

a e P P P c 0 <D ttJ rfl mm P £ Hi P D

id h c ifl a) u

Oli-rl P

> a) p qj H P £ E p ifl id h

Ifl p >1

rH p <L) X", 0) C X P

(fl H P ffl

<up

3

tr> •H

IP

ro CNi

L»( uu y\ tu|S| iuajoi||0OQ uo^djQsqv

37

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prisoner and other persons or animals seldom confuse tile trail.

Obviously, it would be uesirable to study this very sensitive

and selective olfactory process and to see if a transducer

could be developed to make an olfactory analytical instrument

possible

.

Dr. R. B. Murphy, formerly of the MBS staff and currently a member of the faculty at New York University (Dept, of

Chemistry), has written a report on this idea (appendix to ref.

[8]) and found that very little work had been done in the

field. lie did come upon a paper by Fesenko et al. [11] which

showed that it is possible to isolate from the epithelium of

the frog an active substance that is capable of sensitizing a

lipid bilayer to the presence of an odor. The response to the

odor can be seen through the measurement of the electrical

resistance across the bilayer.

In December 1977, Dr. Murphy succeeded in obtaining a separation on Sephadex G-200 of a substance with a molecular

weight of about 330,000 [14]

.

The olfactory activity of the

material was measured by exposing the material to n-butyl

disulfide. Spectrophotometric absorbance at 215 nm showed a linear- log response in two ranges from 10”^ to 10~10 molar and

10” i0 to 10“^~ molar [12]. From these data, it is clear that a

38

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measurable response can be obtained from extremely small

amounts of odorant.

The major task is to understand how selectivity is

obtained. This requires an understanding of the biochemistry

associated with the olfactory process. This study is currently

in progress at NYU (though at a relatively slow pace) and a minimum effort is being made with respect to producing a

transducer that might be used to make an analytical instrument

[13] . The potential of this technique is extremely great and

considerable effort must be expended in order to realize the

goal of an olfactory analytical instrument.

39

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.
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References and notes

1. A demonstration was given in Washington, D.C. of the use of

particle tagging materials in explosives. Particles were

formulated in colored fluorescent layers by 3M Corp. and

ceramic spheres coated with a fluorescent substance were

fabricated by Westinghouse Co. for the Aerospace Corp. The

particles used in these tests were large but could possibly

be made useful for this application as well.

2. a) Velapoldi, R. A., J. Res. Nat. Bur. Stand. 76A, No. 6,

641 (1972) ; b) Reisfeld, R. , ibid, 613 (1972) ; c)

Velapoldi, R. A., Reisfeld, R. , and Boehm, L. , Phys . Chem.

of Glass 14, 101 (1973); d) Reisfeld, R. , Velapoldi, R. A.,

and Boehm, L. , J. Phys. Chem. 7_6, 1293 (1972); e)

Velapoldi, R. A., Travis, J. C., Cassatt, W. A., and Yap,

W. T., J. Microscopy 103 , 293 (1975).

3. Dr. M. F. Dilmore, Inorganic Glass Section, NBS

4. Magnetic particles have been made to enhance their

attachment to iron surfaces. See reference 1.

5. R. M. Henry and D. D. Olson. Fleet Logistic Support

Department and Applied Sciences Department, Naval Weapons

Support Center, Crane, Indiana 47522.

6. Other particle detection systems can be devised that would

make the problem even more intractable. For example Raman

spectra can be taken of particles as small as 1 ym.

7. On the other hand, many die in hostile environments;

presumably the ceramic particles do not.

8. J. R. DeVoe, "Intruder Detection by Chemical Analysis,"

Internal report submitted to the Law Enforcement Standards

Laboratory, NBS and the Defense Nuclear Agency, DOD.

9. While recent literature reports detection of single atoms

(Science 199 1191-3 (1978) ) none of these methods can be

applied to practical samples such as air analysis. Work in

our group has demonstrated practical detection limits that

are very low for solution analysis using dye lasers and

molecular gas analysis using infrared lasers.

41

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10. D. M. Sweger and J. C. Travis, to be published.

11. Fesenko, E. E., Novoselov, V. I., Pervukbin, G. Ya., and

Fesenko, N. K. , Biochen. Biophys . Acta 46_6 347-56 (1977).

12. Murphy, R. B. , Cho, J., and Loxer, J., "Isolation of an

Olfactory Receptor Sensitive to Subnanomolar Odorant

Concentrations," to be published.

13. Some work is being carried out at NYU to determine the best

method to render the active protein insoluble.

14. Recent data obtained by R. B. Murphy show that the

separated fraction contains a mixture of at least 16

different proteins.

15. Moyer, A., Comera, J., Charpentier, H., Jassored, C.,

Applied Optics 1/7 391-2 (1973) .

16. Kelley, P. L. , McClatchey, R. A., Long, R. K., Nelson, A.

S., Optical and Quantum Electronics 8 117-144 (1976).

42

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Appendix A—ASSIGNMENT OF VI BRAT I ON -ROTATION

ENERGY LEVELS IN FORMALDEHYDE

In the infrared region of the electromagnetic spectrum,

molecules absorb radiation by going from one vibrational state

to another. These vibrational states can be decomposed into

normal modes of vibration of the constituents and are quantized

with a quantum number, v. When the three degrees of freedom

each for translational and rotational motion are eliminated,

there are 3N-6 (where N is the number of atoms) , degrees of

freedom remaining; and thus 3N-6 normal modes of vibration.

All molecular vibrations are multiples and/or combinations of

these modes. Within any particular normal vibrational mode

there is a set of energy levels that arise from the rotational

energy of the molecule. In general, these rotational levels

are spaced much closer together in energy than are the

vibrational modes, so that transitions between rotational

levels appear as structure in vibrational bands. The quantum

number associated with the rotation in a molecule is labeled J,

and transitions are allowed for which Av=l and AJ=0,+1. The

structure that is observed on infrared bands is classified as

P, Q or R branches corresponding to transitions for which AJ=-

1, 0 and +1, respectively, where A J=J ' - J" [see eq. (12)]. Each

branch consists of a series of narrow absorption lines that

43

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arise from transitions originating from the various rotational

energy levels and are labeled by the value of J in the lower

vibrational state (usually the ground state) . In a low

resolution infrared spectrum this detailed structure is blended

together, but in medium or high resolution spectra it is often

clearly evident. Figure Al [8] is a medium resolution spectrum

of an uncomplicated band of methyl fluoride and illustrates the

vibrational-rotational structure

.

The infrared spectrum of formaldehyde has been studied in

detail by several researchers [1-7,9]. Since there are four

atoms there are (311-6) =6 normal modes of vibration, as

illustrated in figure A2 [11]. This figure includes the mode

numbering and the frequencies of the modes.

Figure A3 shows the region of the infrared spectrum of

formaldehyde that overlaps with the CO 2 laser emission lines [9].

While this is a complicated spectrum it can be successfully

treated in terms of a strong Coriolis interaction between the

two modes and which causes perturbation on the structure

of these vibrations. Coriolis forces are mechanical forces

introduced as a result of the interaction of linear motion

(vibration) and rotation and are of the form

F = 2mv x w (1)

- c

44

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f\hr\f\

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n

Figure

Al.

Infrared

absorption

spectrum

of

CH
t

/AX

v, = CH STRETCH

v - 2766.4 cm -'

t0

VX /+\ Z'

H »

V2

= CO STRETCH

V = 1746.07 cm

-1

t0

vc

/ \ \ /

H

v 3

= ch 2 scissors

v - 1500.6 cm-' /

v4= ch 2 rocking

v = 1167.21 cm-'

/

V 5

= ANTISYMMETRIC

STRETCH

v - 2843.4 cm~^

0 0

II C ©

© W ^H ©

: = OUT OF PLANE

BENDING

v = 1249.08 cm

-1

Fiyure A2 . Fundamental nodes of formaldehyde.

46

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7 *•’ *2

ji

|40C cm-'

1

1300

3 *2 -1 *0 -i -2 -3

1 +0 -1 -2 -3 -< -5 -6 -7

1250 ii^fyw

4

V

^4

: 2CC

i

"50

-4 -5 -6 -7 -8 -9

no0 CM*' 050 1000

-10 -I! -12 -13 -14

950 c«" 90C 850

Figure A3. Infrared absorption spectrum of formaldehyde.

47

OFFICIAL USE ONLY
where v is the linear velocity of the vibrating atoms and w is

the angular velocity of rotation. These forces can give rise to

other apparent vibrational modes in the molecule and are

illustrated for H 2 CO in figure A4 . If the induced vibration is

close in energy to the initial vibration, a resonance

interaction can occur. The Coriolis resonance will both shift

the positions of the lines and alter relative intensities,

making the spectrum difficult to analyze.

In general any analysis of Coriolis interaction in an

asymmetric rotor is extremely complex and requires large

amounts of computation. However, the problem can be simplified

for formaldehyde by assuming that it is a symmetric rotor. A

measure of the asymmetry of the molecule can be obtained by

Ray's asymmetry parameter [10] given by

if - 2B-A-C

A-C

where A, B and C are the rotational constants and are defined

as

A = — B = C = - - - h

2tt

2 cIA/ 2tt

2 oI b> 2

tt 2 cI c>

V I

B

and I^ are the moments of inertia about the three

principal axes, h is Planck's constant, and c is the velocity

of light. The rotational constants are ordered so that ABC.

Thus the asymmetry parameter becomes -1 for a prolate symmetric

top (B=C) and +1 for an oblate symmetric top (A=B) . In the

48

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3*

o

>1

to o

«e u

>1

49

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Figure

A4

.

Depiction

of

Coriolis

interaction

in

formaldehyde.

The

Vi,

vibrational

mode

induces

the

v0

mode

through

the

Coriolis

interaction

given

by

2m

vxw.

The

symbols

0

and

0

represent

vectors

out

of

and

into

the

page,

respectively,

while

the

superscripts

indicate

the

vibrational

band

associated

with

that
case of formaldehyde, the equilibrium values are A=9. 5795cm

B=l. 3033cm-1 and C=1 . 1462cm-1 giving [4]

K=- .9627

which is quite close to -1. Another parameter that is

especially useful for a slightly asymmetric prolate rotor is

[ 10 ]

b

P

C-B

2A-B-C

_ K+l = K-3

(-0.0094) (3)

This parameter is zero for a symmetric top and increases in

magnitude as the asymmetry increases. One other condition

needs to be evaluated concerning the accuracy in assuming a symmetric top. For an asymmetric top, as well as a symmetric

top, the total angular momentum J and its projection Mj on an

axis fixed in space are considered valid quantum numbers.

However, in an asymmetric rotor the projection of J onto the

molecular axis of symmetry, K is not a valid quantum number.

Thus any attempt to use K is an approximation. Townes and

Schawlow, for a slightly asymetric top, suggest substituting

W = K

2 + c b + c b2 + c b3 +-- (4)

i p 2 p 3 p

and they have tabulated the coefficients c^. However, since b

is so small and K is relatively large in this treatment, this

correction will be ignored.

50

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In the symmetric top approximation, the unperturbed energy

levels are written as [3]

E0

±

( J , K) = v

i + (A

±

-Bi)

2 + B

iJ(J+l) (5)

where B=^(B+C) and is the frequency of band origin. An

absorption will take place between two such levels in different

v^'s. The Coriolis interaction between \> 4

and can be

included as a perturbation, where the differences (in

frequency) between identical rotational levels in and is

[3,9]

A

0 (K)=E° (J,K)-E° (J,K)=v -V + [~(A -B ) - ( A -B )]k 2 (6)

6,4 6 4 6 4 L*6 6 » • 4 4 ^ J

The off-diagonal matrix element in the perturbation is

H = C

a

K (7) 6,4 6,4

a

where £ is called the Coriolis interaction parameter [ 3 , 9 ].

6,4

By solving the secular determinant, the perturbed energy

levels are obtained as

e' (J K) = E° (J K)+ *2 [V (K)-A° (K)l (8)

6,4 6,4 ~ L 6,4 6,4 J

where a' (K) = [

( A

° (K) 2

) + 4 ( £ K ) 2 1

** (9)

6,4 L

' 6,4 1 6^4 J

51

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The S tark Ef fect

The rotational spectrum of a molecule may be expected to be

modified when the molecule is placed into an electric field,

since the field exerts a torque on the dipole moment and

thereby effects its rotational motion. A particular rotational

energy level, J, is thus split into (2J+1) sublevels given by Mj

=-J , -J+l . . . J . When the interaction of the field with the

molecule is calculated by the use of quantum mechanical

perturbation theory, two primary cases emerge. These are the

so-called "first-order" and "second-order" Stark effects, which

derive their names from the type of perturbation approximation

that is the dominant contribution to the energy levels in the

molecule. The first-order Stark effect occurs in molecules

described as symmetric-top rotors, linear molecules under

certain conditions and some slightly asymmetric rotors. The

second-order Stark effect is much more complex, involving

effects of many interacting levels. Fortunately, formaldehyde

is sufficiently close to being a symmetric top that the firstorder theory is sufficient.

For a symmetric top the interaction Hamiltonian II for an

external electric field, E, and an electric dipole moment, y

,

is

H = -M E (10)

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This results in a term value of

w

MK

JTT+XT pE ( 11 )

Then, for a vibrational-rotational transition, the shift in

frequency is

W'-W" = Av U

' M'K'

J' (j'+l)

M"K"

J" ( J"+l) E ( 12 )

where the prime denotes the upper state and double prime the

lower state. Absorption takes place when Av=V]_ aser

~V J • so

as E is increased, various M components of the absorption line

are brought into coincidence with the laser. Defining AM = M

1 -

M" , we can rewrite the equation as

1

E

1

Av

M" M

* K

* (J'+l)

y "K"

J" (J"+l) J + am y ’k* ) j'*j'+1) J (13)

Notice that a plot of 1/E vs. M" will yield a straight line.

The values of Am are determined by the polarization of the

absorbed photons with respect to the external electric field.

If the electric field of the photons is parallel to the

external field, the only allowed transitions are those for

which AM=0. Likewise, for the perpendicular case the only

allowed transitions are those for which AM=+1. While eq. (13)

is quite general, it is useful to rewrite it for particular

cases

53

OmCIALUSEONLY
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AM=0

For aM=0 the intercept terra is zero and the straight line

passes through the origin. This is very useful for

identification of the J quantum number when there are no other

guidelines. One merely starts with an arbitrary number for M"

(which must be an integer) , plots 1/E vs. M" and adjusts the

value of M“max until the line passes through the origin. The

slope of the line is different, depending upon whether the

absorption is in a P, Q or R branch, so these will each be

considered separately.

A. P-branch: J'=J'-1

1/E = fM h m m r

\ Av I J" (J" + 1) (J"-l) |_

( J" +1) K ' - ( J" -1)

I

(

y o \ M"K" f(J- + l)K'

Av j J'TJ^TT) [_(J"-1)K" J

-]

(14)

where it is assumed that the dipole moment is the same for

upper and lower states. If this is not the case one simply

converts all K" to y"K ,! and K' to y'K' and deletes y . o

B. Q-branch

J'=J“

1 - 1 U °

1

1 M"

E l Av J

l j

irTJTr+iy

K"M"

J" (J"+l)

KV

K" (15)

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i

E

o

--(

J'+J ;, +l

\ M" J" K ' - (J"+

I J" (J"+l) KJ"+2)

\ M"K" j" K' , “1

1 j " (j Tr+ry (j"+2) K"

K

M J

(16)

Am=+1

In the case where the polarization is perpendicular to the

field, the slope remains the same as in the previous case.

However, it is possible to obtain more information about the

line assignment by considering the ratio of the slope to

intercept. This ratio has the advantage of eliminating Av,

which is generally unknown. Thus only y'K', y"K" and J" remain,

the latter of which is known from M" max in the previous

section. This leaves only y'K' and y"K" which can in general

be deduced from the slope/intercept. Again, consider the three

cases.

A. P-branch: (J ! =J‘'-1)

1 _ (io) 1 M"l<"

>

”(J"+1)K' _ n 1 + AMK 1 E \ Av / J" (J"+l) _(j ,r-ijK" J

AMK

J"-l

slope = |k^

f j" + l \ /, _ J"-_l K/_\| (18)

intercept AM | J"-l J \ J" + l K"/

Note that the sign is indeterminant until the sign of Am is

known

(17)

55
Q-branch: (J'-J"

)

B

i

E ( Ay ) J" (j"+l) _ M

" K

"(k" 1

) + AMlv '] (19)

slope

intercept

K'-K"

k

,_Em

C. R-branch: (J'=J"+1)

1 _ | y o \ 1

E Uvl j" (J"-' + !)

M"K'

K1 - \J"+2/ K"

slope =: 1 J"K' J

,: +2 K"

intercept AM J"+2 ! - j- K

.

AMJ " K

J" + 2

( 22 )

( 21 )

One additional parameter that is useful for making line

identifications is the relative intensities for successive

lines in a J multiplet. For AM=0 these are given below:

R-branch: I

m « £(J+1) 2 -M2 J

|^(J+1) 2 -K2J / ( J+l) 2

( 2J+1) ( 2J+3) (23)

P-branch: I m «

[

J

2 -M2 J

j^J

2 -K 2 J/J

2 (2J+1) (2J-1) (24)

Q-branch: I_ « M

2 K2 /J 2 (J+l) 2

ill (25)

bote that for both P and R branches the intensity decreases

with increasing M and zero for M=J in the P branch,

while the opposite is true for the 0 branch transitions. For

Am=+1 the intensity pattern is the reverse, so it is relatively

easy to identify Q-branch lines on the basis of intensity.

56

OFFICIAL USE ONLY
OFFICIAL USE ONLY

Experimental

A schematic outline of the experimental apparatus is shown

in figure A5. The laser is a non-commercial C0

2

, flowing gas

laser with a cavity length of 1 meter and active discharge

length of approximately 65 cm. Laser line selection is done by

means of a 2.5 cm diameter, 75 lines per mm grating blazed for

10.5 ym. A ZnSe 90 percent reflecting mirror, with a 2m radius

of curvature, is used as the output coupler, and at least 75

lines can be observed with sufficient intensity for

spectroscopy. Irises are mounted at both ends of the cavity to

confine the laser modes and provide some control on the power

output. The laser frequency is stabilized onto the peak of the

gain curve by sinusoidally modulating the cavity length via a

piezoelectric translator (PZT) and using feedback techniques.

At the heart of the system is the Stark cell, which

consists of two parallel stainless steel electrodes inside a

vacuum chamber, as shown in figure A6 . The electrodes are 40

cm x 6.3 cm x 2.5 cm and are maintained at a precise spacing by

precision ground quartz spacers. Electrical connections to the

plates are made via high voltage vacuum feedthroughs. One

plate is connected to the output of a high voltage operational

power supply in which 9 kHz sine wave modulation, triangular

wave sweep and DC offset voltages are summed and amplified.

57

OFFICIAL USE ONLY
WiHCHt USE ONLY

g s

58

OFFICIAL USE ONLY

Figure

A5.

Schematic

diagram

of

laser

Stark

scanning

apparatus.
OFFICIAL USE ONLY

59

OFFICIAL USE ONLY

Figure

A6

.

Sanple

cell

for

Stark

spectroscopy.
OFFICIAL USE ONLY

The other plate is connected to a DC high voltage power supply

to provide additional bias of up to 5 kV, so that fields as

high as 100 kV/cm can be generated.

In practice, electrical breakdown occurs above 70 kV/cm,

depending upon the internal gas pressure, so data were seldom

taken above 60 kV/cm. As a practical consideration data were

taken in sweeps covering 19 kV/cm with an overlap of 1 kV/cm

between successive sweeps, i.e., 0-19 kV/cm, 18-37 kV/cm, etc.

The spectra were recorded on graph paper with voltage markers

for calibration, and the peak positions were read from the

charts. Sample charts are shown in figures A7 and A8 . While

there are more accurate techniques for measuring peak

positions, they are time consuming and were judged to be

unnecessary for this work.

Formaldehyde monomer was formed by evacuating a small vial

containing paraformaldehyde, sealing off the vacuum pump and

heating the vial until the pressure rose to 50-100 millitorr.

Wo further steps were taken to purify the formaldehyde before

filling the Stark cell. The fill pressure in the cell was

approximately 5 millitorr as measured by a thermocouple gauge

located on the vacuum flange of the cell. At this pressure,

room temperature polymerization and absorption on the walls of

the vacuum chamber are avoided.

60

OFFICIAL USE ONLY
12.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00

55.00

60.00

ELECTRIC

FIELD

(kV/cm)

OFFICIAL USE ONLY

KO

>1 O

<

<ou

3

•H

fa

61

OFFICIAL USE ONLY

n
OFFICIAL USE ONLY

62

OFFICIAL USE ONLY

- 0

e

p. ^-P VD 4-1

• O

ON 0

- 4-S — C

r—

I

0

E-*

P50

Si

+J

0 ON C r-t O I! e

•• o o

u

c

0

440

P

t-DCO 2 rH

II >1»P

4-1 •• •H O

P

C •* 0 r-~ *0 i—

I

•H II

>

44

1

0

T3>i 0

si

0

43

0

tJrH

cdeo

4-1

r-l o

S -

5.3

0 II ^3 0 ••

T30

'OS

O

P

o

0

u

0

4Ho

0

0

c

•H

rH

e 0

B c

P -H P r-l o

0 p & 0

0 0

' 0

44 rH P rH 0 rH

+J o o

03 U 4-1

VO

tna n3

*H C

£ 0

o

rH in

II hi

00<

0

p

0

tx> •rl Cn

1
OFFICIAL USE ONLY

The detector was a commercially available (IIg,Cd) Te

photoconductive detector with a matched preamplifier and a *

of approximately 2x10 cm Hz 2 /watt.

Results

High resolution spectra were obtained in two polarizations.

For one series the laser light was polarized perpendicular to

the Stark field and covered laser lines P(34), P(12), P(10),

P(3), and R(1Q)-R(16) in the 9.6 yrn band. For the other series

the Stark plates were rotated so that the light was parallel to

the Stark field. This latter series included the P(34), P(32),

P(12), R(10)-R(16), and R(20)-R(32) laser lines in the 9.6 ym

band. Several of the spectra as taken directly from the charts

are shown in figures A7 and A8 . Close examination of these

charts reveals the detail and resolution of this technique , as

well as the sensitivity. The signal to noise ratio for high J

( J> 20) transitions is quite good, since for high J transitions

the ground state thermal population is small and this

population must be further partitioned among the (2J+1)

sublevels

Data were derived from the charts, tabulated, and line

identification, for most of the assigned lines, was done

graphically. For AM=0 transitions 1/E for successive

63

OFFICIAL USE ONLY
components was plotted vs. successive integers, Mj, to obtain a straight line. The value of Mmax / and thus the entire axis, was

adjusted so that the line passed through (0,0) [see eqs. (14—

16)] . One such plot is shown in figure A9 , and in general

illustrates the elegances and precision of this technique. The

plot of 1/E vs. M is a straight line regardless of whether AM=0

or +1, so the measured values of 1/E were fit via a linear

regression analysis to a linear function of M. These results

are presented in table Al. If the Stark effect is strictly

first order some information, such as Av and (B'-B u ), can be

obtained from these data. A measure of adequacy of the

assumption of first order can be gotten by the value of

p intercept/slope for AM=+1 lines. For example, for all 05 (d)

lines, the magnitude of the ratio intercept/slope should equal

4, which it does for P

Q._ (5) - pO c (8) . However, note that for the

5 5

higher J values this does not hold, which indicates a departure

from the first order approximation for higher J states.

To the extent that the first order Stark effect is valid

(e.g., for low J) one can calculate Av from eq. (15). From this

one can obtain the frequency of the line by using the relation

Vj=v T -Av if one knows the sign of Av by other means. This

information can be obtained by performing a “pulling 1 '

experiment, i.e., the laser is taken out of feedback control

64

OFFICIAL USE ONLY
OFFICIAL USE ONLY

l _(uio/a>| 3/1

00

<ud

cr •H

4-1C

•H£

d

-PU

<u

o

rH

Pu

o\<

<UP

d

tr> •H

65

OFFICIAL USE ONLY

Quantum

IMumber
<D 'O

>-

.CD

T3

rH

03EM

0

4-4

o

4-t

10 •Hw

>1

rHc

03C

o

•HW

(0

<u

tr

<1>

J-4 M

03<DC

•H

C

(1)

I—

I

XI

flj El
OFFICIAL USE ONLY

G

TJ O U -H

<TJ 4-> U <TJ G -H>

-P 0)

tf) TJ

flj E vo CO in vO CO vo rH CM o co r* co VO in <JV crv O rH CM CO O CM CM CM CM CM CM rH rH rH rH rH rH rH rH rH rH E

VO vo in in VO in in VO in in in in in vo co in in in O O o o o o o o o o O o o o o o o o O O o o

•—

rH rH rH rH rH rH rH rH rH rH rH rH rH rH rH rH •H rH rH rH rH X X X X X X X ! x X X X X

J X X X X X X X X X X X

CO CM VO VO CO vo 00 o> in "3* CM VO CO rH

rH 00 co rH a> rH CO VO CO rH av rH rH rH CO rH ro VO CM

£

X X X X

vo co rH QV CO Ln rH CM

cm oo o in

X X X X X X X X X X X X X

VO CM CO

CO CO rH

CO 00 rH

VO VO

vo

r* *^r

VO rHrrH CM VOCOCO

<JV

CT\ VO O CO

CO VO

X r- X X X

CM 00

vo vo cm a\ o

CM in i-H CM O CM ^ O O CO CO vo

vo co VO COrH<T»COCMCM<^VOVOCOCM r- ^ cm

d)

.Q QJ

ro G

-Q -H 0 J w

M W

0< <

in in m in »n O' O' O O' O'

Gt CU Cu CU CU

VO

CM CM rH CMCM CM OCM CO

CM Loincococococococorococococo O'OO-tGiO^CUCliO^CUO-iCl^CuGiCLi oJ cua«a.cu(i< G.a4 a« cu a. a. a.

i

i

M

aj a) VO VO VO VO VO vo vo O o CM CM CM CM 'sf ^3* H* H" vo VO vo vo VO w c rH rH rH rH rH •H rH CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM m -h J J X X X OS X X X X a: X X 0$ X os X a; X c* c* X

67

OFFICIAL USE ONLY
OFFICIAL USE ONLY

ojg

LD in vo VO vo VO in VO in c 1 1 i 1 1 1 1 1 i 1 i T3 O O O o o o o o o o o o

P -H X rH rH rH rH rH rH rH rH rH rH rH

id -p T3 id >i X X X X X X X X X X X

a -h w

id > ^ 00 00 VO CO a> CO CN

JJ CL) • • • • • • • • o') v rH CN CO vo CO CN CO CN vo in

p

c

o

o

<

<u

XI

<d

E-f

03

•pG

03 rH

XI 0)

id c CA XI -H •H 0 XI W P (/) (P <I

I

c

op

idNH

U

id amaoaximacaama

o

cu

c

o

•H

-PN C

•H O

M *H

<T3 -P

•—I fO O N

03 4J

03 TJ

0) -P

03

O

o

c

•H

u

03

i—

I

2

U

P

03 0) W G

03 -H

PI PI

VO

CM COCM

00 00 00

CM CN CN O O O CN CM CN co co co m co m

T3c

03a

M

03

03

.. .. 4-) < a o

* z

68

OFFICIAL USE ONLY

Parallel

polari
OFFICIAL USE ONLY

and the PZT bias is adjusted so that the laser is operating on

one side of the gain profile. Under these conditions (for

short periods of tine) the frequency is shifted a small amount

in a direction that is known from the physical characteristics

of the PZT. In this case a larger bias voltage on the PZT

lengthens the cavity and reduces the frequency. A laser Stark

spectrum is then taken, compared to the original and the sign

P of Av deduced. Such an experiment was done for Q (5) on

5

R(16) . When the cavity was lengthened the pattern shifted

toward zero field, indicating that v <v . Referring to eq. (5) , for a

PQ branch, the energies in the

symmetric top approximation, ignoring terms in Dj, DJK and D K , are given by

E° (J,K) -E° (J,IC-l)=v +(AA-AB)

2 - (A'-B' ) (2K-1) +ABJ ( J+l)

4 0 4

where AA-A'-A" and AB=B'-B". Then, for energy differences

between lines in the same branch.

E ( J" ,K") -E(J

1 2 " ,K")=AB |j 1 " (J "+l)-j

1 2 (J "+1)2 = 6

or, letting J "ssJ^'+Aj,

6=-Ab Aj(2J + j+1)

69

OFFICIAL USE ONLY
OFFICIAL USE ONLY

P Q (5)-P

Q (8) were used to calculate AB, and the results are

5 5 given below:

P

Q

s (5)

P

Q

s (6)=+. 05590

P

Q (6)

P

Q (7)=+. 06897

5 5 P

Q ( 7

)

P

Q (8)=+. 07990

5 5 P

U

5 (5)-P

Q

s (7)=+. 12491

P

Q (5)-

P

Q (8)=+. 20481

5 5

The average value of AB (-0.004859) is to be compared with the

value of -0.005810 cm“^ as calculated from the reported

constants [5,9]

.

This significant difference probably reflects

the shortcomings of the approximations used.

One can also use the value of Av to obtain the transition

frequency with a reasonably high accuracy for the low J

transitions and from this calculate the Coriolis coupling

a constant, £ . Using this symmetric top approximation the

6 ,

4

value of in eq. (6) can be calculated more precisely than

6 , 4

CL either E° or E°. From eqs. (8) and (9)

,

then £ is found to

6 4 6 ,4

- 1 0t be 10.405 cm x . This is in agreement with a value of K =

6

, - 10.340+0.082 calculated by Nakagawa and Morino [9].

While little new information has been obtained from the

limited spectra obtained to date, this technique has been shown

to be adequate for line identification and has the potential

AB=-. 004658

j AB=-. 004926

| (Avg. -. 004859)

AB=-. 004994 ) A3=-. 004804

Ab=-. 004876

70

OFFICIAL USE ONLY
OFFICIAL USE ONLY

for accurate spectral information. Since little is known about

the isotope shift of C-13 substituted formaldehyde (or other

small molecules of this type) the ability to make line

identifications and derive spectral information by using this

technique is important. Furthermore, the techniques learned by

doing formaldehyde are applicable to other near- symmetric

rotors which include a variety of molecules of interest, such

as methyl mercaptan, for which no high resolution data are

available in the literature.

71
OFFICIAL USE ONLY

References —Appendix A

1. H. H. Blau and J. H. Nielsen, J. Mol. Spectrosc. 1, 124

(1957) .

2. T. Oka, K. Takagi and Y. Morino, J. Mol. Spectrosc. 14, 27

(1964) .

3. T. Nakagawa, H. Kashiwagi, H. Kurihara, and Y. Morino, J.

Mol. Spectrosc. 31, 436 (1969) .

4. K. Yamada, T. Nakagawa, K. Kuchitsu, and Y. Morino, J. Mol.

Spectrosc. 3J3, 70 (1971) .

5. D. R. Johnson, F. J. Lovas and W. H. Kirchhoff, J. Phys.

Chem. Ref. Data, 1, 1011 (1972) .

6. J. W. C. Johns and A. R. W. McKellar, J. Mol. Spectrosc.

48 , 354 (1973)

.

7. J. W. C. Johns and A. R. W. McKellar, J. Chem. Phys. 63 , 1682 (1975)

.

8. W. L. Smith and I. M. Mills, J. Mol. Spectrosc. 11, 11

(1963) .

9. T. Nakagawa and Y. Morino, J. Mol. Spectrosc. 3_0, 84

(1971)

.

10. For a discussion of the spectroscopy of asymmetric and near

symmetric rotors see Townes and Schalow, Microwave Spectroscopy , McGraw-Hill (N.Y.) 1965.

11. N. L. Alpert, W. E. Keiser and H. A. Szymanski, IR Theory

and Practice of Infrared Spectroscopy, Plenum Press (NY)

1970.

72

PFi.LCJAl_liSE.QNLY
NBS-114A (REV. 9-78)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

NBS IR 78-1510

3. Reciprenf s Ao$g$$toti No.

4. TITLE AND SUBTITLE

Intruder Detection Using Trace Constituent Analysis

5. Publication Date May 1979

7. AUTHOR(S) J. R. DeVoe, D. M. Sweger, R. A. Velapoldi

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

11. Contract/Grant No.

12. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City, state, ZIP) Nuclear Surety Directorate

Defense Nuclear Agency

Washington, D.C. 20305

13. Type of Report & Period Covered

ency Code

mini

15. SUPPLEMENTARY NOTES

| | Document describes a computer program; SF-185, FIPS Software Summary, is attached.

16. ABSTRACT (A 200-word or teas factual summary of most significant information. If document includes a significant bibliography or

literature survey, mention it here.) This report documents the progress made during the first year (fiscal year 1977)

of a project to develop intruder tagging and taggant detection systems for use as a component of the forced Entry Deterrent Systems (FEDS) "being developed by the Defense

Nuclear Agency to protect nuclear weapons in storage. Several tagging and detection

techniques were investigated. Glass microsphere particle tags doped with rare earths were fabricated, and a microspectrofluorimeter was used to characterize the

luminescence spectra and determine the detection sensitivity limits for these

uniquely coded particles. Dispensing systems and prototype field detection

instrumentation for particle tagging were also considered.

Initial experiments to develop a gaseous tagging system were directed toward

establishing the limits of detection and the feasibility of isotopic ratio

measurements by the absorption of infrared radiation. The results obtained in the

measurement of the 12 C/ 13 C ratio using a Stark-modulated C0 2 gas laser system and a semiconductor diode laser system are described, and the theoretical development of

techniques for spectral line assignment for simple molecules is discussed in detail.

Concepts for the real-time remote monitoring of trace constituents in the

environment surrounding a storage facility and the detection of contaminating gases

are presented. Preliminary research directed toward the ultimate development of an olfactory sensor transducer is briefly discussed.

17. KEY WORDS (a ix to twelve entries ; alphabetical order; capitalize only the first letter of the first key word unless a proper name;

separated by semicolon*) Fluorescence; infrared absorption spectra; isotopic ratio

measurement; laser infrared absorption; luminescence; olfactory sensing; tagging;

trace constituent analysis; vibration-rotation energy levels.

18. AVAILABILITY Unlimited

IY1 For Official Distribution. Do Not Release to NTIS

I I Order From Sup. of Doc., U.S. Government Printing Office, Washington, DC

20402, SD Stock No. SN003-003-

I I Order From National Technical Information Service (NTIS), Springfield, VA. 22161

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(THIS REPORT)

UNCLASSIFIED

20. SECURITY CLASS

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PRINTED PAGES

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