bluuebunny/crossref_metadata_2025 huggingface dataset:
High Density Optical Disk Master Recorder
Authors: An B.S. , Lee S.H. , Lim E.S. , Cho Y.G. , Yoshikawa T.
Published: February 2023

There are many difficulties to make small pit using a conventional master recorder with visible laser source[1-2]. A master recorder with UV Kr Laser(351nm) has been developed to make narrow pit width for achieving high density optical disk. The authors have developed master recorder which is composed of UV optics and ultra high precision position mechanical system.
High Density Recording Mechanism on Magneto-Optical Disk
Authors: Maeda Takeshi
Published: February 2023

Recording process on magneto-optical disk is divided into two processes. There are both mark forming process and mark reading process. The rules that dominate in these processes are clarified and the high density recording methods based on the rule are described.
Flow Cytometric Ultrasensitive Molecular Quantitation Via Antibody-Antigen Interactions
Authors: Sounders George C. , Jett Jomes H. , Martin John C. , Keller Richard A.
Published: February 2023

The traditional domain of flow cytometry has been the measurement of properties of discrete biological particles - primarily cells or chromosomes. Most flow cytometric fluorescence measurements of cell properties are determinations of the amount of a specific type of molecule in a cell, such as DNA or a cell surface antigen. Since the inception of flow cytometry, there has been a continuing guest for more sensitive instruments and for techniques to detect and quantitate low levels of fluorescence. A generally accepted value for the sensitivity of detection of fluorescein on the surface of a cell is 3 000 to 5 000 molecules.
Comparison of Theoretical Trace Gas Detection Sensitivities for Single-Tone and Two-Tone FM Spectroscopy Using Tunable Diode Lasers
Authors: Chou Nee-Yin , Sachse Glen W.
Published: February 2023

Frequency modulation (FM) spectroscopy has been shown to be one of the fastest growing fields of highly sensitive spectroscopic techniques since it was first introduced by Bjorklund.1 Typically an external electro-optic phase modulator is used to modulate the laser output at radio frequencies where laser noise approaches the shot noise limit. This modulated beam is incident on the photodetector after passing through the absorbing medium. For pure FM, a beat- frequency absorption signal with zero background is obtained. Recently, Janik, Carlisle, and Gallagher2 have devised a new FM modulation/demodulation technique that retains the desirable high frequency modulation yet with low frequency detection. The technique involves simultaneous modulation of the laser beam with two different frequencies, thus the term two-tone modulation.
Detection of Gas Phase Methoxy Radicals by Resonance Enhanced Multiphoton Ionization Spectroscopy
Authors: Long George R. , Johnson Russell D. , Hudgens Jeffrey W.
Published: February 2023

Resonance enhanced multiphoton ionization (REMPI) spectra of CH3O and CD3O between 350-270 nm are reported. The Methoxy radicals were generated by the reaction of F atoms with CH3OH, CH3OD, and CD3OD in a flow reactor. Two band systems are observed in this region. The most prominent feature of the first resides at 320.6 nm in CH3O and at 319.3 nm in CD3O. The second band system consists of two intense transitions at 295.2 nm and 291.5 nm for CH3O and 294.5 nm and 290.7 nm for CD3O. Mass spectra of both isotopic analogues showed that the methoxy molecular ions do not fragment.
Laser Enhanced Flame Ionization Detector
Authors: Cool Terrill A.
Published: February 2023

A proposed "laser enhanced flame ionization detector" is described which retains the desirable properties of conventional flame ionization detectors (FID's), e.g., wide linear dynamic range, a predictable response for hydrocarbon detection, low noise level, and small internal volume, while providing significantly reduced detection limits. This superior detection capability results from improved response characteristics and a thousand-fold increase in ionization rate.
Mapping chemical properties of advanced materials using imaging Raman spectroscopy
Authors: Veirs D. Kirk , Ager Joel W. , Loucks Eric T. , Rosenblatt Gerd M.
Published: February 2023

Partially stabilized zirconia (PSZ) is a microengineered material in which a phase transformation from tetragonal to monoclinic occurs in the stress field surrounding a crack. This transformed zone inhibits further crack growth, thus toughening the material. A complete understanding of the toughening mechanism relies upon a precise measurement of the zone parameters.1 Measurement of the zone parameters requires a spatially resolved technique sensitive to martensitic phase changes in which the atomic composition is unchanged. Raman spectroscopy is a sensitive technique in applications where non-destructive chemical analysis is desired. Spatially resolved Raman spectroscopy where up to 1000 adjacent spatial elements are collected and analyzed simultaneously is possible using a two-dimensional detector and appropriate collection optics and analysis software.2 The spatial resolution, determined by the detector’s spatial resolution and the magnification of the collection optics, can approach 2 μm. Translating the sample in one dimension allows a 2-D map of the chemical composition to be produced efficiently.
The Sensitive Detection and Analyses of SiH3 and SiH Radicals Using Multiphoton Ionization Spectroscopy
Authors: Hudgens Jeffrey W. , Tsai B. P. , Johnson Russell D.
Published: February 2023

The free radicals, silyl (SiH3) and silylidyne (SiH), play important roles at the gas-surface interface during the chemical vapor deposition (CVD) of silicon films from silane, SiH4. We will report recent experiments that enable resonance enhanced multiphoton ionization (REMPI) spectroscopy to detect these radicals with great sensitivity. These newly developed REMPI detection methods should allow experimentalists to measure the relative concentration profile of SiH3, SiH, and Si radicals in the same experimental configuration and under the same conditions. For the SiH3 radical the new spectra will also permit temperature measurements.
Microemulsion Aggregation Numbers Determined by Time-Resolved Luminescence
Authors: Christesen Steven D. , Garlick Stephanie M. , Longo Fred R.
Published: February 2023

The time-resolved luminescence technique developed by Infelta et. al.
1 has been used to measure the aggregation numbers (number
of surfactant molecules per aggregate) for microemulsions containing
cetyltrimethylammonium bromid (CTAB) and cetyltrimethylammonium
chloride (CTAC) as surfactants. Microemulsions are transparent
dispersions of two immiscible liquids (e.g. oil and water) stabilized
by an emulsifier comprising a surfactant and cosurfactant (Figure 1).
The microemulsion aggregates typically have radii of 100-500
Angstroms. Microemulsions are being studied for possible use in
decontamination of toxic organophosphorus compounds.
Near-Field Optics for Exceeding Diffraction Limits in Spectroscopy and Microscopy.
Authors: Harris T. D. , Trautman J. K. , Betzig E.
Published: February 2023

The success of single molecule detection schemes using sheath flow cuvettes as sample cells illustrates the advantage of restricted illumination and probe volume for maximizing detectability or spectroscopy of small objects. The limit to this strategy with conventional optics is diffraction, minimum dimensions of λ/2. The practical limits imposed by physical congestion of optical components may prevent realization of even this limit. The need for optical and spectroscopic characterization of a variety of objects, technological, biological, and chemical, much smaller than λ/2, has driven research toward strategies of optical microscopy with higher resolution.
Resonance Raman and CARS saturation study of the electronic population redistribution processes in metalloporphyrins solutions
Authors: Apanasevich P.A. , Kruglik S.G. , Kvach V.V. , Orlovich V.A.
Published: February 2023

The investigations of fast molecular processes, in which porphyrins complexes with transition metals are involved, is of great importance for elucidating the energy and charge transfer processes in native biological systems. The Ni(II)- and Cu(II)-porphyrins (P) are the promising model compounds to be investigated because of the rich variety of physical- chemical phenomena they demonstrate. To extract information on dynamic behaviour of the molecule usually laser pulses are used having duration comparable or shorter than the excited states lifetimes [1-4]. In the present research we have adopted another approach to obtain transient Raman spectra under deep radiative saturation of one-photon transitions involved. The investigated Me-P have typical decay times in subnanosecond time domain. So, it is possible to produce a quasi-stationary distribution of the molecules over electronic energy levels tracing the temporal profile of the nanosecond laser pulse. As a result Raman spectra from the ground and/or excited states can be recorded and the population redistribution over the excited states can be examined as a function of excitation power.
Molecular Surface Analysis Utilizing Laser Desorption/Laser Ionization
Authors: Lykke Keith R. , Wurz Peter , Parker Deborah H. , Hunt Jerry E. , Pellin Michael J. , Gruen Dieter M.
Published: February 2023

The ability to analyze surface elemental composition has existed for some time. The various methods include Auger Electron Spectroscopy (AES), Secondary Ion Mass Spectrometry (SIMS), and many more.1 However, molecular surface analysis is only now achieving the same sensitivity and selectivity. Molecular surface analysis often utilizes various optical probes: IR Reflection Absorption Spectroscopy, Sum-Frequency (or Second Harmonic) Generation Spectroscopy on Surfaces, etc. These techniques are generally lacking species-specific information. Another approach is to remove the molecule from the surface and probe it in the gas phase, e.g., with state- of-the-art mass spectrometry. Since mass spectrometry offers high resolution and high sensitivity, the remaining problems are removal of the molecule from the surface and ionization without alteration of the molecule (e.g., fragmentation). These pose serious complications for large molecules, in particular. Furthermore, if the molecule of interest is only a minor constituent of a sample, mass resolution and sensitivity are not sufficient for species identification, and a pre- selection in the ionization is often necessary. Our solution is to employ lasers for both desorption from the sample and ionization (post-ionization) of the gas-phase species. The ability to choose the wavelength and intensity of the desorption laser and the post-ionization laser allows for proper tailoring to the needs of the investigation. This will be demonstrated with two examples. First, a vulcanizate (rubber) will be analyzed with a time-of-flight mass spectrometer for the organic additives present in minor concentrations in the near-surface region. Second, a new class of carbon molecules (fullerenes) will be examined with a Fourier transform mass spectrometer.
Investigation of Line Intensities and Collisional Effects in Degenerate Four-Wave Mixing in Nitric Oxide
Authors: Vander Wal R. L. , Farrow R. L. , Rakestraw D. J.
Published: February 2023

The potential of resonant degenerate four-wave mixing (DFWM) as a sensitive, coherent diagnostic probe of combustion species has recently been demonstrated.1,2 Similar to coherent anti-Stokes Raman spectroscopy (CARS), DFWM generates a highly collimated, narrow bandwidth signal beam that allows remote detection, requires minimal optical access, and provides excellent immunity to background luminosity. However, since DFWM is typically performed with resonant radiation, it offers much greater sensitivity than CARS, permitting trace-species detection. While DFWM has been extensively studied in the context of phase conjugation,3 comparatively little has been reported on the development of DFWM for quantitative molecular spectroscopy.
Measurements Of Atmospheric Constituents By Tunable Diode Laser Absorption Spectroscopy
Authors: Fried Alan , Henry Bruce , Drummond James R.
Published: February 2023

The technique of tunable diode laser absorption spectroscopy (TDLAS) offers many advantages in studies relating to the chemistry and physics of the atmosphere. Attributes such as high sensitivity and selectivity, fast response, versatility, absolute and relative response modes, and the potential for high precision have all been used to advantage in such studies. These features and their application to atmospheric measurements will be discussed in the present talk. A brief summary of the fundamentals of the technique will first be given, indicating current limitations and potential future developments. The final and principal part of this talk will focus on an instrument developed at the National Center for Atmospheric Research (NCAR) for high precision ground-based and laboratory measurements.
Recent Developments in Airborne Lidar Measurements of Ozone, Water Vapor, and Aerosols
Authors: Browell Edward V.
Published: February 2023

Major advances have taken place in the last 3 years in the development and application of airborne lidar systems in the measurement of ozone (O3), water vapor (H2O), and aerosols in various regions of the atmosphere. The first simultaneous measurements of O3 and aerosol distributions above and below an aircraft were made in tropospheric investigations in the Arctic during the summer of 1988 as part of the NASA Global Tropospheric Experiment (GTE), and this capability was subsequently used in the 1990 GTE field experiment over Canada. During the 1989 Airborne Arctic Stratospheric Experiment, the first large-scale distributions of O3 and polar stratospheric clouds (at multiple laser wavelengths) were obtained with an airborne lidar system on long-range flights into the wintertime Arctic vortex. An alexandrite laser was used for the first time in airborne lidar measurements of H2O profiles during flight experiments over the Atlantic in the summer of 1989, and improved H2O measurements were made in flight tests during 1990 and 1991.
Two-step, Selective Photoionization of Rubidium Using Ti:sapphire Laser
Authors: Tamura Koji , Oba Masaki , Arisawa Takashi
Published: February 2023

Ti:sapphire laser (TSL) has attracted much interest in recent years because of its broad tunability, high efficiency, and high gain. One of the applications which can be addressed by these unique properties of TSL is isotope separation. Atomic vapor laser isotope separation (AVLIS) uses the selective photoionization of the specific atoms in the atomic beam. This method has been applied to many elements. In most AVLIS studies, dye laser has been used as a tunable laser source. TSL has several advantageous features compared with the conventional dye laser:(1) broad tunable range without changing laser medium; (2) stable operation due to the absence of fluctuation of dye flow; (3) easy handling due to the elimination of toxic dye. Adams et al. have applied CW TSL to the high resolution laser spectroscopy,1) however to our knowledge, TSL has not been applied to the AVLIS process.
Laser Ionization of Biomolecules in Solution
Authors: Murray Kermit K. , Beeson Michelle D. , Russell David H.
Published: February 2023

Many powerful laser based methods are unavailable for the analysis of molecules in solution. Techniques for the analysis of liquids are particularly important for the study of biomolecules, whose natural environment is a water solution. Mass spectrometry is a powerful analytical technique, but liquids and mass spectrometers are fundamentally incompatible. We have developed a technique for laser ionization of biomolecules in solution by applying matrix-assisted laser desorption ionization (MALDI) to liquid aerosols. In the typical MALDI experiment, the analyte biomolecule is deposited from solution onto a metal surface with a 100 to 50,000 molar excess of a suitable matrix, usually a UV absorbing organic acid.1 The solvents are allowed to evaporate and the sample is inserted into the source region of a mass spectrometer. Light from a pulsed laser is absorbed by the matrix causing both ablation of the surface and ionization of the intact biomolecule. In the aerosol MALDI experiment, 2,3 the analyte biomolecule is dissolved in a methanol solution with an ultraviolet absorbing matrix. The aerosol is sprayed into vacuum, desolvated, and ionized by pulsed UV laser radiation. The ions are mass separated in a time-of-flight (TOF) mass spectrometer. Aerosol MALDI mass spectra have been obtained for a variety of peptides and proteins with molecular weights as large as 80,000. We have used aerosol MALDI as a liquid chromatography detection method4 (LC/MS) and as a probe of aerosol and cluster chemistry.5 This paper gives a general description of aerosol MALDI and discusses some recent results for peptide and protein ionization.
Resonant Laser Ablation: Threshold Behavior and Semiquantitative Aspects
Authors: Anderson J. E. , Eiden G. C. , Nogar N. S.
Published: February 2023

Ever since the first report of laser action, it has been recognized that laser ablation (evaporation/volatilization) may provide a useful sampling mechanism for chemical analysis. In particular, laser ablation is rapidly gaining popularity as a method of sample introduction for mass spectrometry. Since its original description, numerous research papers and review articles have appeared on various aspects of laser mass spectrometry.1,2 While most laser ablation/mass spectrometry has been performed with fixed frequency lasers operating at relatively high intensities/fluences (≥108 W/cm2, ≥1 J/cm2), there has been some recent interest in the use of tunable lasers to enhance the ionization yield of selected components in an analytical sample. This process has been termed resonant laser ablation (RLA).3–5 Potential advantages of RLA include: 1) simplification of the mass spectrum, by enhancement of signal from the analyte of interest; 2) improvement of the absolute detection limits by improving the ionization efficiency, and 3) improvement in relative sensitivity by reduction of spurious signal in the detection channel of interest (due to bleed through from adjascent mass channels or from isobaric interferences).
A New Fiber Optic LIF-Sensor for the Detection of Environmental Pollutants
Authors: Schade W. , Bublitz J. , Dickenhausen M. , Grätz M.
Published: February 2023

Time-integrated laser-induced fluorescence (LIF) spectroscopy and fiber optics provide a powerful tool for the diagnostics of various environmental pollutants in different media [1]. The method can easily be adapted for practical applications, e.g. in the trace analysis of oil contaminations in the soil or in the water. Since petroleum products are complicated mixtures of poly- and monocyclic aromatic hydrocarbons their time-resolved fluorescence spectra are described by a sum of up to three exponentials with characteristic intensities ai and decay times τi. For excitation in the uv (337 nm) and observation of the fluorescence at 400 nm decay times τp ≥ 50 ns are obtained for pure oil samples. However, for the same conditions most water and soil samples show very short fluorescence decay times with typical τm≤10 ns [2]. Therefore, time-integrated detection of "early" and "late" fluorescence with respect to the laser pulse can be used very efficient for qualitative and quantitative diagnostics. On the basis of experimental results a computer simulation is developed to show the dependence of the time evolution of the LIF-signals when the concentration of contaminations with long decay times (e.g. polycyclic aromatic hydrocarbons (PAH)) is changed in a polluted water sample [3]. In fig. 1a results of this computer simulation are shown. The left curve corresponds to the fluorescence from dissolved organic matter (DOM) which is always present in natural water. For times t > 60 ns after the laser pulse no fluorescence is obtained. However, when the number density of PAH in the water sample is increased a significant fluorescence signal can be measured for times t>60 ns. Then, time- integrated detection of fluorescence in the time gates 0 to 100 ns (I1) and 100 to 200 ns (I2) with respect to the laser pulse is very efficient method to measure even very low concentrations of PAH in the oil water mixtures. The ratio I2/I1 can be used for qualitative and quantitative diagnostics (refer to fig. 1b).
Fluorescence Spectroscopy on a Single Molecule Basis with a Near-field Spectrometer
Authors: Xie X. Sunney , Dunn Robert C.
Published: February 2023

Recent advances in near-field optical microscopy [1] have offered exciting possibilities for conducting molecular spectroscopy at the nanometer dimension. In particular, fluorescence detection of single chromophores and single proteins containing several chromophores have been achieved using this technique[2][3]. For chemical analysis and biological applications, fluorescence measurements with near-field optics will be particularly informative, providing spectroscopic information not accessible with other scanning probe techniques, such as SEM, STM and AFM.
Near-field Optical Measurements at the Liquid/Air Interface
Authors: Seaver Mark , Frost A. E. , Duncan M. D.
Published: February 2023

Near-field optical microscopy offers the benefit of dramatically improved optical resolution [1] in exchange for working in close proximity (10-50nm) to a thin sample (<20nm). Monolayers at the liquid/air interface fulfill the thin sample criterion and are spectroscopically disctict from the supporting liquid. However, the mobility of the interface suggests that when a tapered probe approaches closely, attractive forces may cause the interface to jump up and submerge the probe at probe-sample spacings much greater than the required working distance for near-field optics. We detect the evanescent field decay above the liquid/air interfaces for glycerol, mineral oil, and water. The ability to measure these evanescent decays demonstrates that near-field approach to the liquid/air interface is possible. The measured evanescent decay lengths agree well with the predicted values. The presence of gravity waves in deep (1-2 cm) liquid samples sets a lower limit on the distance of closest approach but does not prevent near-field measurements.
Population and Thermal Grating Contributions to Degenerate Four-Wave Mixing Line Shapes
Authors: Danehy Paul M. , Friedman-Hill Ernest J. , Farrow Roger L.
Published: February 2023

Degenerate four-wave mixing (DFWM) is a laser-induced grating technique that shows increasing potential as a diagnostic probe for reactive environments. Traditionally, the development of DFWM as a diagnostic for gaseous systems has focused on using the population-grating (PG) mechanism to measure concentration and temperature. Recently, several authors have observed a thermal-grating (TG) mechanism in gases. This mechanism is similar to that observed for many years in liquids and solids.1 The gas-phase thermal-grating mechanism deserves further study since it can complicate population-grating measurements, or can itself be useful for making quantitative measurements.
REMPI/TOF-MS Diagnostics for Monitoring CVD Reactive Intermediates
Authors: Shaw R. W. , Jones L. L. , Feigerle C. S.
Published: February 2023

We have examined the correlation of gas phase species concentrations in a chemical vapor deposition (CVD) reactor with diamond film growth process parameters and film characteristics. The experiments were performed in a hot filament CVD reactor fitted for orifice sampling and resonantly enhanced multiphoton ionization (REMPI) time-of-flight mass spectrometry for gas analysis. The mass spectrometer was used to monitor the chemical species present immediately above the diamond growth surface. Stable products were monitored using electron impact ionization. REMPI was employed for the detection of radicals, including atomic hydrogen and methyl radical, since species such as

CH

3
+

can be artificially produced by dissociative electron impact ionization of stable molecules. Measurements were made of the filament and substrate temperature dependence of the H, CH3, CH4, and C2H2 relative concentrations. Scanning electron microscopy and Raman spectroscopy were utilized to analyze diamond film morphology and quality.
Ultratrace Analysis of Calcium with High Isotopic Selectivity by Resonance Ionization Mass Spectrometry
Authors: Bushaw B.A. , Juston F. , Nörtershäuser W. , Trautmann N. , Voss-de-Haan P. , Wendt K.
Published: February 2023

Using resonance ionization mass spectrometric techniques (RIMS) for
ultratrace analysis has a number of advantages over conventional
techniques: 1. Extremely high sensitivity in the fg to ag range per
sample is possible with the high cross sections for optical
excitation. 2. Ultrahigh elemental and isotopic selectivity is
achieved by the uniqueness of the optical resonance lines of
individual elements and isotopes. 3. Background is strongly suppressed
by subsequent mass spectrometry. Unfortunately, the application of the
technique is complicated by the complexity of the experimental set-up,
particularly the laser system, and hence is limited to a small number
of research institutes so far.
Sensitive Detection of Atmospheric Trace Gases by Laser Photoacoustic Spectroscopy
Authors: Sigrist M.W. , Moeckli M.
Published: February 2023

The sensitive and selective detection of trace gases is of great current interest. Various detection schemes have been proposed including spectroscopic techniques [1]. Recently, diode lasers in the 1.53 µm and 1.65 µm wavelength region have been used for monitoring specific species such as ammonia (NH3) [2,3]. A detection sensitivity of 8 ppb has been reported for laboratory measurements at atmospheric pressure by applying photoacoustic (PA) detection [2] and of 55 ppm-m at a total pressure of 76 Torr by using derivative absorption [3]. However, in order to apply a detection scheme to environmental conditions, a sufficient detection selectivity is often more difficult to achieve than the sensitivity. The stringent requirements are best met by using the fundamental or mid IR region between 3 and 20 µm. Hence, the combination of widely tunable lasers and photoacoustic (PA) detection appears to provide a powerful tool for atmospheric sensing particularly with respect to multicomponent capability, detection sensitivity and selectivity. During the last years we have developed a CO laser-, a mobile CO2 laser- and a continuously tunable, high-pressure CO2 laser-PA system [4]. This paper discusses the main characteristics and most recent results obtained with the mobile system as well as current efforts on novel developments of tunable IR lasers with wide tuning range and narrow bandwidth based on nonlinear optical effects.
Ultrasensitive In Situ Atmospheric Monitoring with a Compact Setup based on Photothermal Deflection (Mirage Effect) Spectroscopy
Authors: Zimering B. L. , Boccara A. C.
Published: February 2023

Photothermal spectroscopic methods, notably photoacoustic, thermal lens and mirage detection, may be seen as alternatives to direct absorption spectroscopy for trace gas detection and offer many advantages, most notably high sensitivity and signal reference to a true zero. While direct absorption measures the typically weak signal difference between input and output energy, photothermal methods measure a signal either directly (thermal lens and mirage detection) or indirectly (photoacoustic) proportional to energy absorbed by the sample.
On the Use of Line Strengths in Applied Diatomic Spectroscopy
Authors: Hornkohl James O. , Parigger C. , Lewis J. W. L.
Published: February 2023

According to a postulate of quantum mechanics, the probability of a transition from state|n′J′M′〉 to state|n″J″M″〉 is controlled by the absolute square of the matrix element 〈n′J′M′|O|n″J″M″〉 in which O is the operator responsible for the transition,Jis the total angular momentum quantum number,Mis the quantum number for thez-component of the total angular momentum, andndenotes all other required quantum numbers. By definition, the sum of all such squared matrix elements which contribute to the same observation is called theline strength.1-4 Thorne’s table 9.13gives the for the Einstein coefficients and the oscillator strength in terms of the electric dipole line strength.
Diode Laser Optogalvanic Spectroscopy for Uranium Isotopic Analysis: Analytical Figures of Merit
Authors: Shaw R. W , Barshick C. M. , Young J. P. , Ramsey J. M.
Published: February 2023

High resolution optogalvanic spectroscopy, excited using near-infrared semiconductor diode lasers, has been utilized for the determination of 235⋃/238⋃ isotopic ratios for uranium and uranium compounds.1,2 The samples ranged from depleted (0.27%) to enriched (20%) 235⋃ abundance. The goal of this effort has been to develop a technique that is suitable for use in the field for measurements at moderate precision. Glow discharge sampling can be conveniently accomplished in such settings, and diode lasers are sufficiently rugged and simple for incorporation into routine instruments. The concept of using high resolution optogalvanic spectroscopy for isotopic analysis has been also considered by Keller3, Tong4, Niemax5, and Edelson6.
Element selective detection in chromatography by diode laser modulation spectrometry
Authors: Niemax Kay , Zybin Aleksandr , Schnürer-Patschan Christoph , Groll Henning
Published: February 2023

Diode lasers of the AlGaAs and InGaAsP types are small and easy to
operate systems. Their wavelength can be tuned by temperature and by
diode current. In particular, the possibility of very rapid tuning by
current is important for wavelength modulation spectrometry which
allows to suppress the 1/f noise, for example, in absorption
measurements. The still limited wavelength range of operation of
commercially available laser diodes (625 < λ < 1600 nm)
can be partly overcome by frequency doubling of laser radiation (SHG)
in non-linear crystals. The power of diode laser wavelength modulation
atomic absorption spectrometry (DL-WMAAS) has been demonstrated
recently by AAS measurements in graphite tube atomizers1,
analytical flames2 and low pressure plasmas3.
The present contribution reports on the application of this technique
for element selective detection in analytical flames and low-pressure
plasmas coupled to HPLC and GC, respectively.
Increasing the Rate of Detection of Single Molecules in Solution
Authors: Davis Lloyd M. , Schneider Laurie E. , Bunfield Dennis H.
Published: February 2023

Single molecule detection in solution offers the prospect of counting individual molecules within small quantities of sample for ultrasensitive chemical analysis [1] and of enabling new approaches for bio-technology applications, such as rapid DNA sequencing and the detection of rare fluorescently-labeled biomolecules. However, further developments in the techniques are required in order to move from the proof-of-principle experiments reported to date, to the level of capability required for realization of the applications. In particular, an increase in the rate at which single molecules can be efficiently detected is required.
Photophysics of Surfactant Molecules in Microdroplets
Authors: Barnes M. D. , Whitten W. B. , Ramsey J. M. , Arnold S.
Published: February 2023

Over the last several years, the study of fluorescence properties in both time and frequency domain of atoms in micron-sized optical cavities has held considerable interest in the physics and quantum optics communities. In addition to fascinating purely scientific aspects of the phenomenon of cavity quantum electrodynamics (QED), the ability to modify molecular fluorescence properties in a microcavity offers potentially significant sensitivity advantages for ultrasensitive - or, single molecule - fluorescence detection. For example, two important quantities which limit sensitivity in single molecule fluorescence detection - the saturated absorption rate and the integrated fluorescence yield - can be significantly increased by enhancing the fluorescence decay rate. We have shown previously that fluorescence decay rates1 as well as the integrated fluorescence yield2 of rhodamine 6G can be significantly enhanced in glycerol microdroplets. However, exploitation of these effects in order to gain sensitivity in single molecule fluorescence detection is nontrivial for at least two important reasons. First, the magnitude of decay rate enhancement depends on the position of the molecule within the droplet; molecules near the center of the droplet are not coupled to high Q resonances while molecules near the surface may strongly interact with cavity resonances associated with droplet. Thus, diffusion limits the amount of time a given molecule may interact with the resonances thereby limiting the fluorescence decay rate. Second, the fluorescence decay rate depends on the orientation of the transition moment with respect to the cavity "axis"; e.g., the surface normal for spherical cavities.
Novel Rare-Earth Doped Chalcogenide Glasses for High-Brightness, Room-Temperature, Broad-Band Infrared Sources
Authors: Moon J. A. , Harbison B. B. , Sanghera J. S. , Aggarwal I. D.
Published: February 2023

For many infrared spectroscopic applications in the 3-5 μm spectral region, a compact, fiber optic and fiber optically pumped source of infrared radiation is needed [1]. In many cases, the ultimate detection limit of an infrared chemical sensor can be improved by increasing the optical “brightness” or radiance (in Wcm−2Sr−1μm) of the source, and not necessarily increasing the source’s total optical power. The radiance R
bb
of a black-body “glow-bar” source in the 3-5 μm region is practically limited by the source’s temperature to around R
bb
≃ 0.17 Wcm−2Sr−1μm−1 (T=1100K, λ = 4.5 μm.) Optically pumped fluorescent sources do not suffer from this limitation, and have several other important advantages over blackbody sources. These other advantages include remote location, compact size, insensitivity to electrical interference, room temperature operation, and non-reactivity with harsh or explosive environments.
Single Particle Back Scatter Measurements with Size Parameters Near One
Authors: Hart Matthew , Bruce C.W.
Published: February 2023

We have developed a technique to measure the back scatter from particles using millimeter wavelengths. The system consists of two major components, the microwave source/receiving setup and the scattering chamber (lined with microwave absorbing material) [Fig. 1]. Millimeter wavelengths are used and thus size parameters near one are natural targets for the system. A waveguide horn antenna is utilized as both the source and the receiver. Ambient radiation, due to chamber reflections and antenna mismatch, is a major source of error in the system and is minimized by way of a cancellation bridge. The bridge adds to the received radiation a signal of equal amplitude and of opposite phase to the ambient leaving only the desired back scatter component. Although confined to the small (25 cm radius) vessel we have been able to perform far field measurements with good results.
Alternative Approaches to Sampling and Data Collection for Laser Induced Breakdown Spectroscopy (LIBS)
Authors: Miziolek Andrzej W. , Williamson Cindy , McNesby Kevin L. , Fell Nicholas F. , Medlin Stephen V. , Forch Brad E. , Daniel Robert G. , Cespedes Ernesto R. , Miles Brian H. , Cortes Javier
Published: February 2023

LIBS is a very powerful technique for spectrochemical analysis, particularly for the detection of metals in vapors, aerosols, liquids, and solids. Much of the pioneering work in LIBS development has occurred at Los Alamos National Laboratory1. Typically, a short-pulse laser beam is focussed into the sample causing optical breakdown and the plasma light is collected unto a spectrograph and detected by an array detector. This relatively straightforward set-up affords high sensitivity and efficiency in terms of data generation and collection. In traditional LIBS analyses a single laser is used to vaporize and ionize the sample.
Laser-Induced Plasma Spectroscopy (LIPS) for Environmental Applications
Authors: Haisch C. , Clara M. , Panne U. , Niessner R.
Published: February 2023

Laser-Induced Plasma Spectroscopy (LIPS) is a powerful instrument for quantitative elemental analysis of solid, liquid and gaseous matrices. For LIPS an intense, pulsed laser beam is focused on the sample of interest, resulting in the dissociation and partial ionisation of the sample in an expanding plasma cloud. Approximately 100 ns after the laser pulse recombination followed by relaxation of the atoms can be observed in the plasma cloud. The spectrally and temporally resolved detection of the atomic emission lines reveals analytical information about the elemental composition of a sample. The lack of sample preparation and the low costs for a single measurement make this technique a useful tool for environment analysis. The presented applications are excellent examples for the versatility of LIPS.
Tunable InP based semiconductor lasers for gas analysis
Authors: Broberg Björn , Nilsson Stefan , Rigole Pierre-Jean , Klinga Tiina , Bäckbom Lena , Stålnacke Björn
Published: February 2023

Fiber optics communications has been the driving force for research on
advanced semiconductor lasers based on InGaAsP-InP. Thus, single
frequency and tunable lasers with good modulation properties have been
developed. The normal wavelength range achievable in the InGaAsP-InP
system is ca 1.2-1.67μm. However, using compressively strained
quantum wells the wavelength range can be extended to ca 2μm.
We have exploited this possibility, by modifications of
telecommunications laser designs and processes, to fabricate very
compact, rugged and potentially cheap application specific
semiconductor lasers suitable for gas analysis. These lasers find
applications in instrumentation for real-time industrial process
control, smoke-stack emission and environmental monitoring etc. The
technology has advantages such as a high sensitivity for many
important gases, an unsurpassed selectivity, short response time, and
is inherently explosion-proof.
Imaging and Time-Resolved Spectroscopy of Single Molecules
Authors: Harris T. D. , Macklin J. J. , Trautman J. K. , Brus L. E.
Published: February 2023

Recent progress in the fluorescence detection of individual molecules [1-8] suggests that a single dye molecule can be a useful tool to probe chemical identity and activity. Measurement of fluorescence lifetime [5,6] and spectrum [6] can be augmented by knowledge of molecular orientation using polarized light [3], and triplet [2] and photoisomer excitation, as well as diffusion processes, via fluorescence-intensity correlation. Applications of fluorescent probes include the study of the dynamic conformation of membrane-bound proteins, transport of and signaling by messenger molecules, and the optical detection of the sequence of DNA. While molecules can be spatially located using near-field microscopy [5-8], near-field probes can perturb the molecule under study. We show here that molecular properties can be determined easily and in a non-perturbative manner using far-field illumination, and we obtain unperturbed spectral and lifetime data that cannot be extracted from an ensemble measurement.
How many labeled mononucleotide molecules can be identified in water on the single-molecule level
Authors: Sauer M. , Arden-Jacob J. , Drexhage K. H. , Göbel F. , Lieberwirth U. , Zander C. , Wolfrum J.
Published: February 2023

One of the most popular application of the single-molecule detection
(SMD) technique is fast DNA sequencing on the single-molecule level as
proposed by Keller and coworkers.1,2 The principle idea of this very
elegant method involves the incorporation of fluorescently labeled
mononucleotides in a growing DNA strand, attachment of a single
labeled DNA to a support (generally latex beads), movement of the
supported DNA into a flowing sample stream, microchannel or
microcapillary3 and detection of the analyte molecules as they are
cleaved from the DNA strand by an exonuclease. The DNA sequence is
determined by the order in which differently labeled nucleotides are
detected and identified. Although a lot of problems are associated
with the enzymatic incorporation of labeled mononucleotides and the
selective handling of a single DNA strand different detection and
identification strategies have been developed. However, up to now,
only two different dyes have been successfully identified on the
single-molecule level in aqueous solution due to their different
fluorescence lifetimes.4,5 Hence, the critical question in DNA
sequencing on the single strand is how many labels can be identified
on the single-molecule level in aqueous solvent systems.
High Speed Microchip Electrophoresis
Authors: Jacobson Stephen C. , Culbertson Christopher T. , Ramsey J. Michael
Published: February 2023

Open tubular separations in the liquid phase including capillary electrophoresis are conventionally practiced in capillary tubes with diameters of tens of micrometers and lengths of tens of centimeters. Structures having similar dimensions can be fabricated on planar substrates using micromachining techniques. Microfabricated separation devices have been demonstrated for capillary electrophoresis,1 2 synchronized cyclic electrophoresis,3 and free-flow electrophoresis.4 The separation performance hinges upon minimizing the spatial extent of the injection plug and detector observation region, and optimizing the separation field strength. The injection plug width can be minimized by fabricating narrow channel dimensions for the injection valve, and the detector observation region can be minimized by having a small excitation volume or tight spatial filtering for fluorescence detection. For high speed separations, the separation column does not have to be long, e.g., < 1 mm long. Unfortunately, the footprint of these microfluidic devices is usually > 200 mm2, but the channel manifold can be designed such that the potential drop is small in areas not contributing to the separation. This results in a maximum field strength in the separation column. Because the resistance in the channel is proportional to the length and inversely proportional to the cross-sectional area, thin channels are fabricated for the injection valve and separation column, and wide channels for all other sections of the channel manifold.
Interferometrically-decoded fibre-optic vibration sensor using low-power laser diode
Authors: Gangopadhyay Tarun Kumar , Henderson Philip James
Published: February 2023

Laser-based sensors have a number of significant advantages over other sensors for monitoring of vibration. Proper control of vibration may prevent deformation of components, failure of machineries and also unwanted vibrational sound hazard (as an environmental remediation). Applications of laser with fibre-optic technologies are providing a new approach to vibration monitoring in electromechanical equipment. Evolution of vibration signature is a recognised hallmark of equipment degradation [1,2]. Optical fibre sensors using laser interferometry are particularly suited to this application because of their inherent electrical isolation, superb dielectric properties and immunity to electromagnetic interference.
Near-Infrared Frequency Modulated Detection of Transient Species
Authors: Marr Andrew J. , Chang Bor-Chen , Hall Gregory E. , Sears Trevor J.
Published: February 2023

Recently, a frequency modulated Ti:sapphire laser was used as a highly sensitive means for detection of transient species (1). In particular it was used to measure spectra of methylene and its halo-derivatives (2,3) and in addition very high signal-to-noise Doppler lineshapes were recorded from which significant dynamical analyses have derived (4). Within the last year we have incorporated the frequency modulation (FM) method into a near-infrared diode laser system which works at wavelengths around 1 μm and this has produced an order of magnitude improvment in signal-to-noise of that system. A further improvement in sensitivity has been achieved by extending the interaction region of the probing laser and the gas sample using a Herriott-type cell. Systems based upon this diode laser spectrometer which is cheap, simple to use and maintain, and relatively compact may provide a sensitive monitor of important gaseous molecules that absorb at similar wavelengths.
Instantaneous Velocity Field Measurements of Air Flows by Ozone Tagging Velocimetry (OTV)
Authors: Ribarov Lubomir A. , Wehrmeyer Joseph A. , Pitz Robert W. , DeBarber Peter A.
Published: February 2023

Although species concentrations and temperature are routinely measured by laser-molecular interactions (laser-induced fluorescence, Raman scattering), velocity is most often measured by the introduction of foreign seed particles, such as oil droplets or ceramic particles. Particle-imaging velocimetry systems are commercially available and provide velocity field measurements based on time-of-flight data from many particles. However, seeding non-uniformities and particle drag can lead to differences between the particle and gas velocity fields. Environmental and operational issues discourage the introduction of particles into large wind tunnel test facilities.
Laser diode refractive index detection in capillary.
Authors: V.L. Kasyutich
Published: February 2023

A cylindrical sample cell (capillary) is used widely in photothermal lens spectroscopy [1-4], refractive index (RI) detectors for microbore liquid chromatography [5,6] and capillary electrophoresis [7-9], in analysis of fluids [10,11]. An inner diameter of the capillary can be varied from hundreds down to tens microns and laser sources are appreciable for probing of the samples in the capillary.
Mid-Infrared Laser Source for Gas Sensing Based on Frequency-Converted Diode Lasers
Authors: Bamford Douglas J. , Petrov Konstantin , Ryan Andrew T. , Patterson Thomas L. , Huang Lee , Hui David , Field Simon J.
Published: February 2023

Compact, room-temperature mid-infrared laser sources have a variety of
applications in the quantitative detection of gases. For example, many
gases of importance for atmospheric science can be detected
quantitatively using strong absorption lines in this spectral region.
We are developing a room temperature mid-IR laser source based on the
frequency mixing of two diode lasers in periodically poled lithium
niobate (PPLN). This laser source has been used to measure strong
absorption lines of water vapor (at 2.7 μm), methane (at 3.4
μm) and carbon dioxide (at 4.3 μm).
Theoretical Investigation of Phase Matching Schemes for Degenerate Four-Wave Mixing Spectroscopy
Authors: Reichardt Thomas A. , Lucht Robert P.
Published: February 2023

Degenerate four-wave mixing (DFWM) spectroscopy is a potentially powerful technique for quantitative measurement of minor species in gas-phase media [1-3]. In this paper we compare the DFWM signal levels and lineshapes obtained using two different phase-matching geometries: the phase-conjugate geometry and the forward phase-matched geometry. DFWM signal levels are calculated by solving the time-dependent density matrix equations using direct numerical integration (DNI) [4, 5] for a two-level system interacting with three laser beams. This numerical analysis includes the effects of molecular motion, intermolecular collisions, and high laser intensities, all of which have been shown to affect the DFWM signal level.
Characterization of mechanical modification of anchored surfactants using sum-frequency generation
Authors: Furtak T. E. , Chow B. C.
Published: February 2023

We have used optical sum-frequency generation to reveal the structure and orientation of organic monolayers self-assembled on dielectric surfaces. We studied the influence of mechanical modification, as occurs with rubbed display windows and model lubricants.