PB 161574

^ecknical ^T,ote 73

SOME EXPERIMENTS ON

THE DEPOSITION OF

GASES AT 4.2* K

«

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NATIONAL BUREAU OF STANDARDS

technical ^Tiote

73

OCTOBER 1960

SOME EXPERrMENTS ON

THE DEPOSITION OF

GASES AT 4.2'* K

T. Baurer

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ie t Some Experiments on the Deposition of Gases at 4.2 °K

tt Theodore Baurer

National Bureau o£ Standards, Washington 25, D.C.

In order to develop some preliminary information

concerning the very basic problems of gaseous

deposition at extremely low teiq>eratures, sauries

of argon, nitrogen, oxygen, and hydrogen were

deposited at 4.2 ^'K, and variations in some of

the parameters associated with these depositions

were observed. In addition, savaplea of the saioe

gases were passed through an excitation zone

prior to deposition, and differences in the deposition behavior were recorded. The pressure

downstream of the deposition region and the

ten^erature within the deposited solids were

found, in general, to increase with flow rate

of the depositing substances, and to vary with

time in a manner depending on the density, flow

rate, and state of excitation of the incoming

gases. Arrhenius curves were plotted using walnnup data observed in these experiments and solidphase transition data determined elsewhere. Variations in the positions of these plots were sometimes the result of differences in the conditions

of deposition, and at other times an effect of the

chemical nature of the gas studied. The experimental behavior of hydrogen, relative to that of

the other gases studied, was observed to be

strongly dependent upon its much higher thermal

conductivity.

INTRODUCTION

The method of Broida and Pellam [1] for trapping energetic

species at or below liquid helium ten5)eratures has been used

ie ~———

— ————

This research was performed under the National Bureau of

Standards Free Radicals Research Program supported by the

Department of the Army.

Presented before the 138th national meeting of the American

Chemical Society, New York City, September 1960.

tt

•Guest scientist from Grumman Aircraft Engineering Corporation,

Bethpage, L.I., N.Y.

- 1 -
extensively, both in the experimental program on the nature of

free radicals at the National Bureau of Standards [2] and in

related programs elsewhere [3]. However, those who have worked

with this method have often been handicapped in the interpretation of their experimental results by a lack of fundamental

knowledge as to the detailed nature of gaseous deposition at

low temperatures.

The necessity has been recognized for obtaining experimental data and developing theories relevant to the following

aspects of the problem: (a) flow parameters for gases moving

toward cold surfaces; (b) mass, energy, and momentum interactions associated with collisions between gases and cold

surfaces; (c) modes of crystal growth of deposits at extremely

low teiq)eratures; (d) surface mobilities of newly deposited

species as a function of matrix conq>osition; (e) the tendency

of deposited species to escape back to the gas phase during

continuing deposition; (f) chemical interactions at or on cold

surfaces; (g) mechanisms of distribution and absorption of

energy within and through the solid deposits; and (h) effects

of all these factors upon the physical and chemical changes

occurring as the deposited materials are revaporized dviring

warm-up

A conq)lete set of answers to these basic problems cannot

be immediately forthcoming. In the present work we have investigated some of these aspects in order to provide preliminary

information concerning the broad area of gaseous deposition at

extremely low teTi5)eratures.

APPARATUS

The gases used in this work, viz., high-purity argon,

nitrogen, oxygen, and hydrogen, were deposited both in their

ground states and in a mixture of excited states produced by

passage through a microwave (2450 Mc) electrodeless discharge

zone.

The basic deposition vessel, shown in figure 1, was the

heart of the vacuum apparatus used in this work. As can be

seen, this vessel consisted of a group of four coaxial tubes.

The outermost of these provided the deposition surface and

enclosed the system. The innermost tube acted as a gas inlet

route. Gases were drawn directly from their cylinders through

Tygon tubing to dry ice-acetone traps and thence through flowmeters to a gas inlet manifold and the deposition vessel. The

flowmeter tubes were used more to provide a measure of constancy of flow than to meter the flow, inasmuch as the gases flowed

- 2 -
at tank pressures, with no attempt being made to adjust to

atmospheric pressure. The manner of measuring actual flow rate

will be described below.

The two intermediate tubes within the deposition vessel

were connected at their lower ends and formed a warming jacket,

the inside of which was open to the atmosphere or to circulating

dry nitrogen at room teiq>erature. The use of this jacket prevented precooling of the incoming gas prior to its impingement

upon the deposition surface at the bottom of the outermost tube.

An additional thin tube was suspended from a ring- seal at the

jacket inlet stopcock and hung freely within the jacket walls.

This provided a means for bringing in the dry nitrogen for

warming the jacket, and insured good circulation through the

jacket.

The annulus between the innermost tube and the jacket

provided, by suitable arrangement of the gas inlet manifold,

an additional gas inlet when desired. On the other hand, the

annulus between the warming jacket and the outermost tube led

to a dead end. This region, as seen in figure 1, was downstream

from the deposition surface, with respect to the incoming gas.

Pressure in this downstream region could be monitored during

deposition. During a run, therefore, the only means of removing

incoming gases was the cold surface; there was no other pump in

that part of the system once the downstream portion was closed

off.

The inside of the innermost tube was coated with General

Electric Dri-Film (R) 88, a mixture of silicones. The purpose

of this coating was to minimize the wall-catalyzed recombination

of dissociated gases, especially hydrogen, which had been passed

through the microwave discharge zone. Wittke and Dicke [4] have

reported a similar treatment, and justified its use solely on

the basis of "crude quantitative tests" of its wall-poisoning

effectiveness as corcpared with that of several other treatments

(p. 625, 22^ cit. ) , The effectiveness of the treatment used in

the present work was not tested at all, it being assumed that

the silicone coating obtained was at least as effective as that

of Wittke and Dicke,

Two copper-constantan thermocouples were incorporated into

the construction of the deposition vessel. One of these was

sealed through the bottom of the outermost tube of the deposition vessel, and was made to lie on the deposition surface in

such a way as to measure temperatures within the deposited

solids. The other was placed in the end of the innermost tube

to provide a measure of the constancy of incoming gas terqjerature

- 3 -
prior to deposition. Flow of dry nitrogen through the warming

jacket could usually be so adjusted as to maintain this tenqperature to within 5% of 240 *K. Calibration of the thermocouples

was carried out in liquid helivun, hydrogen, and nitrogen, and

was in agreement with calibrations of similar thermocouples, as

carried out by Dr. Norman L. Brown of the National Bureau of

Standards Free Radicals Research Program, who extrapolated his

values to a curve drawn to correspond in shape to curves taken

from Southard and Andrews [5] and from Aston, Willihnganz, and

Messerly [6]. The uncertainty in thermocouple readings was

always ± 1 microvolt, which corresponded to approximately

± 0.65 **, 0.15 ", 0.06 ", and 0.05 "K at the boiling points of

helium, hydrogen, nitrogen, and oxygen, respectively.

Immediately below the deposition vessel was a double dewar

containing liquid helium with liquid-nitrogen and double-vacuum

jacketing. It could be raised to surround the deposition

vessel, or it could be lowered away from the vessel, by a manuallyoperated jack, so as to provide refrigerant at any desired level.

By suitable manipulation of the liquid helium level at varying

distances below the deposition surface, tenqjerature at the glass

could be regulated to within about 5% of any desired value.

Above the deposition vessel and mounted aroiind the gas

inlet tubes leading to it were waveguides connected to two microwave generators. These provided microwave electrodeless discharges at 2450 Mc and a maximum of 125 watts, for exciting and

dissociating incoming gases, when desired.

Pressure in the downstream region of the deposition apparatus

was measured by a Pirani gage and by a cold cathode ionization

gage. A second Pirani gage was located in the upstream portion

of the innermost gas inlet tube. Elsewhere in the system, an

ordinary mercury manometer was available for measuring over-all

system pressure, and a McLeod gage was available for calibration.

For all pressure measurements in the refrigerated part of the

system, thermal transpiration corrections were made whenever the

measured pressure was less than 65 microns Hg, the various gages

themselves being always at room temperature.

The deposition vessel was connected through a gas inlet

manifold of rather coiq)lex design and through a main manifold to

the main p\uq)ing system. Finally, a portion of the system

designed for measuring total volume of gases deposited consisted

of the manometer mentioned above, a known volume (871 cc) , and a Toepler punp.

- 4 -
PROCEDURE

In a typical run, the gas flowed into the system past one of

the waveguides and through the cylindrical gas inlet route. It

was then condensed on the circular surface at the bottom of the

deposition vessel. The level of liquid helium in physical contact with the vessel was maintained as closely as possible in

the plane of the deposition surface. The only exception to this

rule was in the case of hydrogen, for which the helium level

always had to be held somewhat higher, in approximately the

plane of the end of the jacket. Downstream pressure and the

temperature in the deposit were observed regularly, sometimes

at minute-by-minute intervals, throughout the deposition. In

addition, upstream pressure and the teiiq>erature of the incoming

gas stream were monitored and the liquid helium level was

adjusted whenever necessary. The deposit could be observed at

all times through an unsilvered vertical strip in the helium

dewar.

Upon the termination of deposition, the inflowing gases were

cut off and the helium level was usually brought up high enough

on the deposition vessel to immerse the entire glass section

containing the solids deposited. Gas circulation in the warming

jacket was stopped, and the jacket was evacuated by rough-pun5)ing.

The decays of downstream pressure and deposit temperature were

usually followed after gas cut-off until they had reached equilibrium levels.

The condensate was then allowed to begin warming. This was

accon^lished either by mechanically lowering the helium dewar,

or by allowing the liquid helium level to drop slowly below the

deposition surface, as the helium boiled off. Measurements of

pressure over and temperature within the deposit were made as

the warm-up proceeded. If enough liquid helium still remained

when warm-up had proceeded to some ten^ierature slightly below

the normal boiling point, the deposition surface was again

immersed in refrigerant, and the gas redeposited and revaporized

for as many cycles as possible.

Finally, the total amount of gas originally deposited was

permitted to flow to the gas measurement section of the apparatus.

This was usually done piecemeal, the last bits of significant

voluDoe increments being cycled through the Toepler pump. After

each volume of gas was measured, it was punped out of the system.

The true flow rate of the depositing gas was then determined

from the total volume thus measured, as reduced to standard

conditions, integrated over the total time of deposition.

- 5 -
RESULTS

The variations of downstream pressure and deposit terapeva.-

ture with time and flow rate during the depositions of both

ground- state (undischarged) and excited (discharged) argon,

nitrogen, oxygen, and hydrogen are charted in figures 2-12. The

measured parameters generally increased for all four gases as functions of flow rate. They also increased for nitrogen and

oxygen as functions of excitation regardless of flow rate.

In addition, the downstream pressure increased with time

for argon, excited argon, nitrogen, oxygen, and excited oxygen

at constant high flow rates (greater than 50 standard cc/min)

the same parameter decreased with time for oxygen and hydrogen

at lower flow rates; and it tended to be invariant with time

for argon, excited argon, and nitrogen at and below 50 standard

cc/min, and for hydrogen and excited hydrogen at high flow rates.

The variation of pressure with time for excited nitrogen was

erratic.

The geometrical form of the various deposits ranged from

truncated cones, the radius of the truncation corresponding

approximately to the radius of the gas inlet tube, to disk- shaped

solids. The tendency to cone formation usually increased for

greater amounts of total material deposited. Because of these

variations in form, it proved inqjossible to determine any consistent value of thermal conductivity of any of the solids. In

the case of hydrogen, a rather fluffy solid was laid down on the

deposition surface and also on the nearby vertical surfaces. All

deposits were white, except for the well-known blue-green color

associated with excited nitrogen [7].

For gases admitted to the system (at 17-152 standard cc/min)

through the cylindrical inlet tube, the observed upstream pressures

were coii5)ared with Poiseuille pipe-flow calculations. The observed

values in every instance deviated from calculated values by a factor no greater than two in either direction.

Figures 13-15 are the warm-up curves for ground- state (undischarged) and excited (discharged) argon, nitrogen, and oxygen,

respectively. The corresponding curves for hydrogen are not

shown, since these warm-up data were inconsistent. The curves of

figures 13-15 were drawn as a series of straight lines, and the

pertinent data are summarized, with appropriate annotations, in

Table I. It may not appear from these graphs that the curves

always correspond to the experimental points as closely as might

be desired. This is because the straight lines were based only

partially on the experimental points shown; additional data used

- 6 -
in plotting these lines were the known transition phenomena

summarized in the last column of Table I [8].

Considering the curves as drawn, some differences appeared

in the warm-up data for first vaporizations as opposed to later

vaporizations, and for the discharged gases as opposed to the

ground- state gases. These differences will be discussed below.

Certain effects associated with the warm-ups may be cited

here. In the case of discharged nitrogen, for exaii?)le, the

characteristic glows described and spectroscopically analyzed in

many papers of Broida and his co-workers [9] were observed. In

addition, the single run with discharged oxygen was terminated

by an explosion which was attributed to the presence of ozone in

the solids deposited [10], This explosion occurred when the

pressure in the system had reached about 400 mm Hg, during the

gas- transfer and volume-measurement phase of the run. As a

result, the flow rate in this instance had to be estimated from

the available data,

DISCUSSION

It was noted above that in general, both downstream pressure

and temperature of the solid during deposition increased as functions of the flow rate of any given incoming gas. This manner

of variation was probably a result of increasing amounts of heat

released at the condensation surface as increasing amounts of

gas were deposited, per unit time.

In a similar fashion, the increases observed for the same two

variables as functions of the excitation of nitrogen and oxygen

indicated significant increases in the energy released on condensation of the excited species when compared with the respective

ground- state molecules. The same effect was not as marked, and

may not even have occurred, for argon. This probably reflected a higher degree of reversibility of the modes of energy absorption

for gaseous nitrogen or oxygen than for argon flowing through the

same energy discharge zone at coii5)arable molar flow rates. That

is, argon was capable of more efficiently storing its excitation

energy in the solid phase than the other gases, a conclusion which

is further substantiated below. The observed results for hydrogen

were marginal, and may have been masked by thermal conductivity

effects which are discussed more fully below.

Where any variation of downstream pressure with respect to

time of condensation was observed under given conditions of gas

conqjosition, excitation, and flow rate, this was probably the

- 7 -
principal effect of a slower approach to djmamic equilibrium in

the particular system studied than in other systems where downstream pressure was relatively constant with time. The generalized trend of such variations was that the downstream pressure

tended to: (a) decrease with time for low-density gases at low

flow rate; (b) increase with time for high-density gases at high

flow rate, or for high-densiliy gases passed through the discharge

zone; and (c) remain invariant with time for intermediate cases.

Behavioral differences between hydrogen and the other gases

studied manifested themselves in several respects, as may be

seen by conqjaring the data of figures 10-12 with those of figures

2-9. For one thing, it was noted earlier that in order to obtain

hydrogen deposits at all, the liquid helium level had to be kept

higher on the deposition vessel than for the other three gases

studied. Any time the liquid helium level was allowed to drop

appreciably, the rate of hydrogen deposition dropped sharply,

as evidenced by surging downstream pressure in the system. Also,

it was not possible, as in the other cases, to prevent precooling

of incoming hydrogen by the use of the warming jacket filled with

flowing nitrogen at room teiq)erature ; great quantities of nitrogen

quickly condensed to liquid in the jacket, and measured ten^erature of the inflowing hydrogen dropped to 77 °K or slightly below.

This probably was partially responsible for the greater and more

consistent deviations of the observed head pressure, e.g. 58-787.,

from values predicted by the Poiseuille calculations for flowing

hydrogen than for the other gases.

Again, whereas downstream pressures in depositing argon,

nitrogen, and oxygen were usually of the order of 10"^ to 10"'' mm Hg

depending on the flow rate, they were observed to be much higher,

e.g. 10"-^ to 10"^ mm Hg, for hydrogen at comparable flow rates.

Thus hydrogen exhibited much lower probabilities of sticking,

under the conditions of this work, than the other gases. Finally,

it has already been pointed out that the behavior of the hydrogen

deposits on warm-up was so erratic as to lead to wholly inconsistent data which could not be plotted with any degree of reliability.

The effects described above are qualitatively understandable,

however, when we take into account that these are basically thermal

transport phenomena which have been observed, and that the thermal

conductivity of gaseous hydrogen is anywhere from six to eight

times that of the other three gases studied. Thus, it would be

expected that hydrogen would behave differently and be harder to

handle, as was the case.

- 8 -
In an effort to evaluate the deposition data in terms of

some unifying principle, an attempt was made to correlate these

data with the predictions of a simple theoretical model* derived

from considerations of thermal balance in the deposit. The

assuiqjtion was made here that the measured downstream pressure

might be considered as a measure of teroperature at the surface

of the deposit, as opposed to the observed deposit tenqjerature

which was taken from the interior of the solids. The results of

calculations based on this model were inconsistent and totally

inconclusive. It is believed that the negative results of this

phase of the work were due to nonequilibrium effects in the

deposit, as for exaiiq>le, heat generation accompanying crystalline

rearrangement during the deposition. Thus, the model could not

Ve applied to these experiments.

The available warm-up data have been summarized in figures

13-15 and Table I, As noted above, no consistent warm-up data

were obtained for hydrogen, so this discussion will be confined

to considerations affecting only argon, nitrogen, and oxygen.

Several features relating to these data are worthy of comment

at this point.

It will be noted, first of all, that the warm-up curves for

any one gas underwent a shift on going from the unexcited to the

excited case. For argon (fig, 13), this shift (from portions

B,C,D to E,F,G) was in the direction of higher pressure at any

given tenqperature for the excited gas. This reflects a greater

release of energy in the form of additional amounts of vaporizing species at any given temperature, when the argon had been

energized in the discharge prior to its original deposition,

A similar effect was noted in nitrogen (fig, 14), except

that the extent of the shift (from portions C,D,E to G,H,J) may

not have been very significant when the scatter of points in

these regions is taken into account.

In the case of oxygen (fig. 15) , the observed shift was in

the opposite direction for the excited gas, i.e., to lower pressure

at any given tenqperature . Again in this instance the extent of

the shift (from portion C to D) may not have been significant. It

could be argued that since the amount of ozone vaporizing from the

-ifFor this model, I am indebted to Dr. Sidney Golden of Brandeis

University, consultant to the National Bureau of Standards Free

Radicals Research Program.

- 9 -
condensate had to be two moles for every three moles of oxygen

originally reacting (302 -> 2O3) , a sufficient quantity of ozone

storage in the condensate of excited oxygen could explain such

a shift in the vapor pressure curve as is shovm in figure 15.

However, it would be very difficult to prove that this actually

happened in this work.

Let it be supposed that the shifts noted in the nitrogen

and oxygen vapor pressure curves were indeed of minor significance, and that the vaporization of excited species from these

condensates released approximately the same amounts of energy

as the vaporization of the respective ground-state molecules,

while the extent of the energy shift from ground-state to

excited argon deposits on vaporization was somewhat more substantial. Under this assumption, conqsarison of these results

with the observed variations in the deposition parameters for

the various ground-state and excited gases leads to the conclusion that energy storage was more efficient in the case of the

argon deposits than for nitrogen or oxygen, where greater

amounts of energy were released in the course of the original

condensation. The case of hydrogen is, as stated earlier,

marginal or inconclusive on the evidence of these experiments,

but would be expected to parallel the case of the other diatomic

gases. The greater amounts of energy release on condensation

of the diatomic gases is probably a direct effect of recombination mechanisms in these gases as they impinge on the respective

deposits. Such mechanisms do not, of course, come into consideration in the deexcitation of argon.

In addition, portions of the warm-up curves for both groundstate and excited argon, and for excited oxygen, may be seen in

figures 13 and 15 to have shifted in one direction or another

with varying degrees of significance, in going from the first

vaporization of the respective deposits to later vaporizations

of the redeposited materials. In the case of ground- state

argon (fig. 13), the shifts from portions C,D to C«,D' indicate

lower energy releases at temperatures below 35 "K for later

vaporizations than for the first vaporization. This may reflect

a greater degree of ordering in the crystalline argon during

the relatively rapid redepositions of this gas than diiring the

slower first deposition. This effect is particularly significant over portions D and D*, i.e., at temperatures less than

about 10 °K, and may not truly exist between 10 ° and 35 "K,

i.e., over portions C and C. In excited argon, on the other

hand (fig. 13), the marginally significant shift from portion

G to G' is in the direction of greater energy release on later

vaporizations, at ten^eratures below 10 °K, indicating the

possible loss by the solid phase of additional increments of the

- 10 -
original discharge energy upon revaporization of the same

material.

In figure 15, a shift is observed on going from the first

to subsequent vaporizations of excited oxygen (containing ozone)

This shift, from portions B,D to F,E appears to be anomalous

unless we again argue the storage of large quantities of o.zone in the deposit, and postulate further that the ratio of gaseous

ozone to oxygen was higher during later warm-ups than on the

first vaporization. We do know that ozone was present because

of the explosion mentioned earlier and the references cited in

[10]. We also know that portion E of figure 15 is the only

case of a warm-up curve with a negative slope as observed and

plotted, i.e., a negative heat of sublimation as shown in

Table I-C. The reasons for this are not clear, but might also

relate to the release of ozone in the later warm-ups on a

scale which had not been realized in the first vaporization.

However, it should be pointed out at this point that portions

F and E. were derived from only one run, number 303, which

because of the explosion which terminated it was never repeated. We therefore know nothing about the reproducibility

of these portions, except that junction FE does correspond to

ja known physical phenomenon (cf . Table I-C)

Finally, portion F of the nitrogen warm-up curves in

figure 14 marks a phase which, as noted in Table I-B, exists

only for nitrogen deposited at low flow rates. In the particular run in which the points determining this part of the curve

were recorded (no. 201), the flow rate was 17 standard cc/min.

No runs were carried out with excited nitrogen at any con^arably low flow rate.

CONCLUSIONS

The following conclusions have been drawn from this work:

1. In the condensation of gases at extremely low tenqjeratures, the amount of heat released at the cold surface varies

directly as the volume flow rate of the depositing species.

Corresponding increases occur in such parameters as the pressure

in a closed volume downstream of the deposit and the tenqjerature

within the deposit.

2. In such condensations, the downstream pressure tends

to: (a) decrease with time for low-density gases at low flow

rate; (b) increase with time for high-density gases at high flow

rate, or for high-density gases subjected to excitation before

- 11 -
deposition; and (c) remain invariant with time for intermediate

cases. Where the extremes of time variation are observed, the

flowing system may be considered to undergo a slower approach

to dynamic equilibrium than is true of the time- independent

cases.

3. Upon warm-up of the solids described in this study,

sufficient regularity of pressure and tei]q>erature variation is

attainable in all cases except hydrogen, so that Arrhenius plots

may be drawn which are reasonably consistent with solid-phase

transition data determined elsewhere.

4. The available evidence indicates that monatomic gases

subjected to excitation prior to deposition are capable of

storing ^greater quantities of their excitation energy in the

solid phase than diatomic gases siioilarly treated. In the

latter case, it appears that recombination of dissociated

molecules prior to or coincidental with condensation leads to

the loss of significant amoiints of excitation energy from the

condensate. These considerations may be modified in the case

of excited oxygen because of the formation of ozone.

5. During warm-up of deposited gases, some shifting of

the Arrhenius plots may occur as a result of repeated depositionvaporization cycles with the same gas saiiq>le. The reasons for

these shifts may be tentatively assigned to energy effects

within the solids deposited. This effect appears to be particularly significant for ground-state argon at teiqperatxires below

10 'K.

6. The behavior of gases In such deposition-vaporization

cycles as were carried out in this work is much more erratic

and difficult to control for gases of relatively high thermal

conductivity, as Illustrated by the case of hydrogen.

These experimental data and conclusions have provided information which we hope will lead to a fuller understanding of

gaseous deposition at very low teiq>eratures. It is yet too

early to formulate a theory consistent with all the known facts

regarding this phenomenon.

ACKNOWLEDGMENTS

The author wishes to express his appreciation to Drs. Herbert

P. Broida and Arnold M. Bass, who were respectively Chief and

Assistant Chief of the N.B.S. Free Radicals Research Section when

this work was done, and to many other members of the Section for

- 12 -
much help and encouragement. To Mr. Alfred K. Stober, thanks

are especially due for much valuable aid and many suggestions

relating to the experimental set-up and procedures.

Dr. Miriam Sidran of Grumman Aircraft Engineering Corporation rendered invaluable assistance in rewriting and editing

this paper from its original form as a National Bureau of

Standards report.

LITERATURE CITED

[1] H.P. Broida and J.R. Pellam, Phys. Rev. 95, 845 (1954);

U.S. Patent No. 2,892,766 (1959).

[2] H.P. Broida, Endeavour 17, 208 (1958).

[3] See, for exaii5)le: D.E. Milligan, H.W. Brown, and G. Pimentel,

J. Chem. Phys. 25, 1080 (1956); C.K. Jen et al., Phys. Rev.

104, 846 (1956), Ibid. 112, 1169 (1958); S.N. Foner and

R.L. Hudson, J. Chem. Phys. 28, 719 (1958), Ibid. 29, 442

(1958) .

[4] J.P. Wittke ami R.H. Dicke, Phys. Rev. 103, 620 (1956).

[5] J.C. Southard and D.H. Andrews, J. Franklin Inst. 207, 323

(1929) .

[6] J.G. Aston, E. Willihnganz, and G.H. Messerly, J. Am. Chem.

Soc. 57, 1642 (1935).

[7] L. Vegard, Comm. Leiden 205b, 49 (1930).

[8] The author is indebted to H.S. Peiser of the National Bureau

of Standards for having furnished these descriptions of

phenomena associated with the recorded break-points. The

descriptions are drawn from data of Peiser and his co-workers

in the low temperature X-ray laboratory at N.B.S., and from

published data by other workers, as given in the following

references: W.F. Giauque and J.G. Clayton, J. Am. Chem.

Soc. 55, 4875 (1933); R.W.G. Wyckoff, "Crystal Structures",

Vol. I, Chap. II, pp. 14 and 17, Interscience, New York,

1951; D. Vorlander and W.H. Keesom, Comm. Leiden 182c

(1926); L. Vegard, Z. Phys. 58, 497 (1929), Ibid. 79, 471

(1932) ; M. Ruhemann, Z. Phys. 76, 368 (1932) ; K. Clusius,

Z. phys. Chem. B3, 41 (1929).

- 13 -
[9] M. Peyron and H.P. Broida, J. Chem. Phys. 30, 139 (1959);

M. Peyron et al.. Ibid. 1304.

[10] H.P. Broida and J.R. Pellam, J. Chem. Phys. 23, 409 (1955);

K.B. Harvey and A.M. Bass, J. Mol. Spectrosc. 2, 405 (1958);

R.A. Ruehrwein and J.S. Hashman, J. Chem. Phys. 30, 823 (1959)

- 14 -
Table I. Summary of Warm-up Data

A. Argon (fig. 13)

Letter Indices

Associated Phenomena and

Comments

for: Ten^). or Pressure Heat of Nature of

Vapor Break Range or Range Sublimation Transition

Curves Points

State:

TK) (mm Hfi) (cal/mole)* [8]

GroundA > 66.7 > 30 1860 (See Notation,

fig. 13)

AB 66.7 30 Appearance of

Liquid Phase

B 66.7-33.3- 30-0.0016 1300

BC 35.7 0.0045 Annealing

BC« 33.3 0.0016 Annealing

C 35.7-12.1 0.0045 to

1.27x10-6

297

C 33.3- 9.3 0.0016 to

1.80x10-8

292

CD 12.1 1.27x10-6 Recorded

Transition

CD' 9.3 1.80x10-8 Recorded

Transition

D < 12.1 < 1.27x10-6 35.4

D« < 9.3 < 1.80x10-8 34.9

Excited ••

AE 66.7 30 Appearance of

Liquid Phase

E 66.7-36.4 30 - 0.6 623

EF 36.4 0.6 Annealing

F 36.4- 9.6 0.6 to

4.0x10-6

309

FG 9.6 4.0x10-6 Recorded

Transition

FG» 10.3 1.28x10-5 Recorded

Transition

G < 9.6 < 4.0x10-6 32.9

G» < 10.3 < 1.28x10-5 34.5

From Arrhenius calculations.

- 15 -
Table I (Continued)

B. Nitrogen (fig. 14)

Associated Phenomena and

Letter Indices

Temp, or Pressure

Comments

for: Heat of Nature of

Vapor Break Range or Range Sublimation Transition

Curves Points TK) (mrnHg) (cal/mole)* [8]

Ground-State:

A > 59.0 > 49 1670 (S(ee Notation,

fig. 14)

AB 59.0 49 Appearance of

Liquid Phase

B 59.0-35.6 49-0.37 867

BC 35.6 0.37 Phase Change

C 35.6-31.0 0.37-0.25 187

CD 31.0 0.25 Secondary Change,

Restricted Rotation,

Possible Vapor

Pressure Effect.

E

DE

EF

31.0-22.5 0.25 to 1130

2.5x10-4

22.5 2.5x10-4

22.5-12.6 2.5x10-4 to 256

2.8x10-6

12.6 2.8x10-6

Annealing

Transition at

Low Flow Rates

of Deposition only,

F < 12.6 < 2.8x10-6 18.0

Excited:

BG 35.6 0.37 Phase Change

6 35.6-31.0 0.37-0.275 141

6H 31.0 0.275 Secondary Change

as for CD (above)

H 31.0-22.5 0.275 to

0.0027

754

HJ 22.5 0.0027 Annealing

J < 22.5 < 0.0027 303

From Arrhenius calculations.

- 16 -
Table I (Concluded)

Associated Phenomena and

Letter Indices

r: Temp, or Pressure

Comments

fo Heat of Nature of

Vapor Break Range or Range Sublimation Transition

Curves Points

State:

(°K) (umi Hg) (cal/mole)* [8]

GroundA > 59.0 > 6.0 1760 (s ee Notation,

fig. 15)

AB 59.0 6.0 Appearance of

Liquid Phase

6 59.0-25.0 6.0 to

2.9x10-^

855

BC 28.6 0.00185 Ordering (Annealin

C < 28.6 < 0.00185 258

Excited •

BD 25.0 2.9x10-^ Transition from

Glass to P-Crystal

D < 25.0 < 2.9x10-'^ 246

AF 59.0 6.0 Appearance of

Liquid Phase

F 59.0-25.0 6.0 to

4.7x10-6

1210

FE 25.0 4.7x10-6 Transition as in

BD (above)

E < 25.0 > 4.7x10-6 - 82,8

From Arrhenius calculations.

- 17 -

stop Cock

35/25 Boll Socket

Pyrex Glass

Uranium Glass

7052 Glass

T.C. Wire of Side View

Kovar Tubing

Copper Wire

Constanton Wire

Seal

T.C. Wire

18/9 Ball Socket

SIDE VIEW

Figure 1. The deposition vessel.
iO 20 30 40 50 60 70 O DO

20 40 60 80

Time (min )

100 120 140 A

Figure 2. Variation of downstream pressure during

deposition of groxind- state argon.
D / < A

•r 1 c 4

\< 1

V.ou

f> ^ 1

ro* f / \ to

01

O 6

CO OOO 00 »f>- f t, o 1 / 1 cr

({> 1 <> <!

OZ o

u. (> 1 1"

UJ i 1 1 -1 UJ

-J 6 / <i z

CVJ N- U>^ c3 O o oc1 * ^ 1 ( > / ^ f < 1 f\E O D 0<1 (t)

(P o 4 ^-^ Or

-r-"r° 1 ? t ' 1 (1 1 0\ ^J ^-^ \ <{ ^^ "^ ^ \, 1 1 1 ,i— ,-^~~^~^4 0'

—

<\ja

N 2 o

bJO U

CD U>

a

U> K)

(U -Ma

*-> * CO CO «0 N 1 'Oa o o =) «0 (\J ~

^Htao

U> (M ^H

lO - a ~ X

•1-1 4->

m

O •H

03

Ph

IS «o

a> 60

Fj H- 00 •iH 00 U

:i TJ 2 o — Q) « 00 c ;h E •«->

cti *0 (^ fl. h E 0) 1- 9r

(M ^ B m (o <0

*-»

•!-> •H

00 «Dn

CM in

O

Phv * OO TJ

<M ^r ^o

CJ o o o <M * •l-t M

n) •H

(0 (M — (O

^1 >

CM • - CJ CO

(Uu

CO 52 00 - * CO o o h

(0 CMm

00 CM o 10

(Xe) 9'>"|DJ9dUJ3X IjSOddQ
(>ie) 8Jn4Dj8duJ9i iisodaQ

m

CM CO o(M -r- N

-r00 -r

o —

o

z

Ulo

UJ

-1

c1

u

u

•6

tn

Sio

tco

in

(M

c

00o o

o

E X +

c > o

S E

0- ifo

c

O O

c

«* Q 8

eo >

+-^

Of o o 3 W Q

Z

3

o

<0

N

m

p n

s

CO -8

_

. o

o o

( 6h uiiu) sjnssdJd uroaJisuMOQ

C

o

bOu

V

u

o

00o

0) 73

&0

•iH

T3

0) 2

n)u

a,

OQO

a

00

OQ

0)

O

o

o

>

u

bO

••H (X4
10 " -

X

E

E

3

(/) (A

0>

E

a

10

4= 10

C

o

o

10

LEGEND

Symbol Run No. Flow Rote (Std. cc /min)

O 202 75.88

D 204 55.96

O 201 16.87

-4

~

jj Cutoff

-5

1 Cutoff

/ l^>^^o ^<r-^-^-0^

? Cutoff

-6

[ \^ ^>--^>

( >

-7

1 1 I 1 1 1 iO 20 30 40 50 60 70

Time (min ) Figure 5. Variation of downstream pressure during

deposition of ground- state nitrogen.
Uio

UI Euu

•o

(7)o

a:oozoE D

r 1 1 Ii?i

~-?--s, I 1

(0 (M OO 9 O «0 lO lO M CM M — <M «0- s •

0)00o

<»•

M

<o .ti

P!V s 13•uaI -d3oh N to

•o **-t od

<B o » 4^•H

OBOa«

•d

00 ? .sh3

'c •d

(0

C

V^

«> :i E 15 8 ^ h

0)9<B S 9> 4J

•iHao N P*«

•O

O <«-i (M oco•H

(0 *

<«

••Hh

(tf

N >• vO « «M

3> - * h

(Xe) dJnjOjadujdi jisodaQ
LEGEND

Symbol Run No.

203

205

Flow Rate (Std. cc /min)

46.27

43.42

10

-2 _

Cutoff

10 3_

M

10 -5 .

(P)

Region of Ropidty

+„^ —4- Measurements

<!{. Cutoff . Downstream

Varying

of Pr essure

H--K

Cutoff

Cutoff

Note:

Solid Lines Denote Pressure Variation.

Dashed Lines Denote Temperature Variation.

1 1 J. 1 j_L 1 1 J lJ I

32

^

26

24

CLE

.9*

M

O

Q.

9> O

10 15

12 16

20

20

25 30 (P)

24 26 32 35 (T)

Time (min)

Figure 7. Variation of downstream pressure and

deposit temperature during deposition

of excited nitrogen.
20 24 28 32 36 40 44 46 52

Time (min

)

Figure 8, Variation of downstream pressure during

deposition of ground- state and excited oxygen.
E

00

>^

a c

I

o o

V bo

O -ri a a

O

u a,

ti 0)

o^V

•H

(>lo) d<in|0J3duidi ijsodao
M

C

3

o

Time (min)

Figure 10, Variation of downstreajn pressure during

deposition of ground- state hydrogen.
Symbof

LEGEND

Run No. Flow Rote (Std. cc /min)

25

404 120.9

a 402 8.709

20

^

J5

e

3

Ow

<UOl

E

o

Q.

O

Note:

Dotted Lines Denote

Interpolations

[]

I0()

QCutoff

—o—

o

't

10

Figure 11,

20 30 40 50 60

Time ( min ) Variation of deposit temperature during

deposition of ground- state hydrogen.
10'

c

h

LEGEND

Run No. Flow Rote Std.cc/min

405 151.9

Cutoff

Note:

Solid Lines Denote

Pressure Variotion

Dashed Lines Denote

Temperature Variation

Dotted Lines Denote

Interpolation

- 30

10- « -

10-

35

25

20

IS

o

•

E•

8

&

10

10 20 30 40 50 60 70

Time ( min ) Figure 12. Variation of downstream pressure and

deposit temperature during deposition

of excited hydrogen.

i
10

10'

10'

10"

10'

E 10- E

A ^^66.7 "K

36.4 "K.

10 ° -

10^

Vaporizatlont

Flr»t

Subtsqutnt

LEGEND

Undiichorgcd Argon 6 (B.C.O) .« (B.C'.tf)

Oltchorgtd Argon •B - (E.F.G)

(E,F,G')

Solid Line A = Tobic Voluat » * Th«NBS-NACA Tables of Thermol Properties of Gases , Table 19.50 , July , 1950.

33.3 °K

\^ -<-M

-10.3 "K.

9.6 °k."-

10

10

\ •^ \

\

\

9.3°K.-2

.o

•-..c D

•-..e

O

©•

K) J I I I L. .02 UJ4 .06 .08 .10 .12 .14 .16 M .20 .22 .24

Reclprocol Temperature (°K)'

Figure 13, Warm-up curves for all argon deposits,
10'

10*

10"

I0-'

10"'

6 10" E

"• 10*

10*'

n-«

10

-59.0 °K.

LEGEND

Veporlxotlont Undltchorgtd NItfsgan OtschorgM Nitro^^n

Flf»f e <8.C,0.E.F) —Q" - (8,0. H.J)

Subsequent ^__ (8.C.0,E.F) .-..(.- (B.G.H.J).

SoUd UN A • ToWt Vokwt « « Tfw N8S- NACA ToblM of Thermal PrepcrtiM of ToW* 11.30, July, 1950

dL$^3I.O-K

JHr ".0 It

;-' f O

fl-.H

.»&

22.5

^>—22.5«K

' V.a

\

12.6 OKdft^^

D •.

J I i_ J I I I L. -i L

.02 .04 .06 .08 .10 .12 .14 .16 J8 .20 .22 .24

RKlprocai Tcmparatur* (°K )*' Figure 14. Warm-up curves for all nitrogen deposits,
10'

10'

10

10"

6 10 E

10

10"

10

10'

Vaporizations

Subsequent

LEGEND

Undischarged Oxygen (B.C ) A (B.C)

Solid Line A • Table Values ' ¥The NBS-NACA Tables of Thermal Properties of GosM , Table 9.S0 , December , 1949 -59.0 "K

Dischorged Oiygen •D (B.D) (E.F)

.02 .04 .06 .06 .10

Reciprocal Temperature (°K) Figure 15. Warm-up curves for all oxygen deposits.

USCOMM~DC

3NT OF COMMERC]

Frederick H. Mueller, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director

THE NATIONAL BUREAtJ OF STANDARDS

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