bluuebunny/crossref_metadata_2025 huggingface dataset:
Super Resolution Disk with a Photochromic Mask Layer
Authors: Tsujioka Tsuyoshi , Kume Minoru , Horikawa Yukio , Ishikawa Atsushi , Irie Masahiro
Published: February 2023

Continuous efforts have been made to increase the recording density of optical memories because of the ever growing demands for high-speed and large data computing as well as for high-quality video recording. Super resolution disk technologies such as magnetically induced super resolution (MSR), which is one of the practical approaches, require a mask layer which shows a nonlinear response to the light intensity. Super resolution technique using photon-mode photochromic organic dye is expected to be applicable to any kind of recording layer, e.g., read-only, magnetooptical, phase change and so on, since the mask layer's response is independent of the recording layer and the mask layer is capable of high sensitivity. This paper presents a discussion on a super resolution disk with a photochromic mask layer.
Direct Overwrite Magneto-Optical Disks with Magnetic Super Resolution Readout Function
Authors: Fujii Yoshio , Tokunaga Takashi
Published: February 2023

In order to realize the higher recording density of LIMDOW-MO(Laser intensity modulation direct overwrite magneto-optical) disks, we have studied on adding the MSR(magnetic super resolution1)) function to it2). In LIMDOW-MSR disks, i) sufficient MSR read power margin and erase power margin, ii) a narrow erased fringe width, which may cause the erasure of marks on the adjacent track (cross erase), to narrow the track pitch and iii) the same or less writing energy compared with conventional LIMDOW disks to avoid the thermal damage on active layers are required. In this paper, we describe the suitable threshold temperature design for LIMDOW-MSR disks.
Super-High Density Optical Disk using Deep Groove method
Authors: Morita Seiji , Nishiyama Madoka , Konishi Hiroshi , Matsumoto Hiroyuki , Niwa Tatsuo
Published: February 2023

For the purpose to achieve large capacity and high density of optical disks, it is indispensable to narrow the track pitch. The track pitch decides the distance between recorded marks on a track and the adjacent track. To narrow the track pitch, the following two technical issues should be settled. One of the issues is the optical cross-talk from the adjacent track, the other is the thermal cross-talk to the adjacent track. (This thermal cross-talk is often called “cross-erase”.) For suppressing the optical cross-talk, the land/groove recording method1)and the magnetic super-resolution method2)have already been reported. Meanwhile, there is no report which clarifies how to decrease the thermal cross-talk. In the actual cases, the lower limit of the track pitch depends on the thermal cross-talk3). This paper describes the suppression of the thermal cross-talk by adjusting the groove depth more deeply. We call this technology “Deep Groove method”.
Recovering the Affine Transformation of Images by Using Moments and Invariant Axes
Authors: Lee Morris
Published: February 2023

The affine transformations of images are recovered in real-time with a closed-form solution using moments to find invariant axes in planar objects.
Robust Estimation of Shape from Shading
Authors: Ferrie F.P. , Lagarde J.
Published: February 2023

We have developed a solution to the problem of obtaining robust estimates of surface orientation from local analysis of shading. By robust we mean an algorithm that can cope with general, but realistic, assumptions about local surface geometry, in order to be tolerant of image noise and of imprecise estimates of light source direction. It is based on the minimization of a residual form that measures the total deviation from an implicit model of surface curvature. This model is similar to the one used by [3,6,7] in local estimation of shape from shading, but it is less restrictive. In fact, one may view our procedure as a second stage of processing that interprets these local estimates of shape subject to constraints about how the (differential) geometry of the surface can change between neighbouring estimates. Our experiments show that the algorithm not only improves the noise immunity of the local method, but also "undoes" some of the distortion that is incurred as a result of assumptions in the local shading model [3]. Practical machine vision applications based on this approach are a possibility given the development of low-cost parallel processing hardware.
Discrete Fourier Transform Based Depth-from-Focus
Authors: Bove V. Michael
Published: February 2023

A method is demonstrated for estimating range by using two-dimensional DFT’s to measure focus differences between images taken with two different lens apertures.
Efficient Estimation for Markov Random Fields
Authors: Swain Michael J. , Wixson Lambert E.
Published: February 2023

The problem of assigning labels from a fixed set to each member of a set of sites appears at all levels of computer vision. Recently, an optimization algorithm known as Highest Confidence First (HCF) [Chou, 1988] has been applied to labeling tasks in low-level vision. Examples of such tasks include edge detection, in which each inter-pixel site must be labeled as either edge or non-edge, and the integration of intensity and sparse depth data for the labeling of depth discontinuities and the generation of dense depth estimates. In these tasks, it often outperforms conventional optimization techniques such as simulated annealing[Geman and Geman, 1984], Monte Carlo sampling[Marroquin, 1985], and Iterative Conditional Modes (ICM) estimation[Besag, 1986].
Direct measurement of volume of arbitrarily shaped piles from binocular stereo images
Authors: Hunt Neil , Nishihara H. K.
Published: February 2023

We present a method for measuring the volume of an irregularly shaped pile of material from a stereo pair of images without computing its surface shape.

Our method is applicable to such tasks as verifying the volume of solder paste applied to the pads of a circuit board prior to reflow soldering. It can be implemented using the stereo hardware of Nishihara [1984] to perform at a rate of one or more volume measurements per video frame time.
Brain Structural Mapping during Stereotactic Surgery for Movement Disorders Using Optical Reflectance Spectroscopy
Authors: Liu Hanli , Giller Cole. A. , Johns Maureen
Published: February 2023

Precise localization of anatomic structures within the brain is crucial to neurosurgeons. In this paper, we report our recent investigation of using a low-cost, miniaturized, optical reflectance (elastic) spectroscopy device to obtain, in real-time, brain structural mapping during stereotactic surgery for movement disorders. 20 subjects were studied with IRB approval during temporal lobectomy or stereotactic surgery. The Measurement results show that this instrument along with our developed algorithm allows us to distinguish white and gray matter with a resolution of 1 mm. The technique is extremely easy in practice, and the equipment is inexpensive, miniature, and provides real-time brain structural mapping and localization in the operating room.
Application of the confocal opto-acoustic tomography in detection of squamous epithelial carcinoma at early stages
Authors: Oraevsky Alexander , Savateeva Elena V. , Karabutov Alexander A. , Bell Brent , Johnigan Richard , Pasricha Jay P. , Motamedi Massoud
Published: February 2023

Confocal opto-acoustic transducer (COAT) was developed and applied for detection of early stages of squamous cell carcinoma in hamster model of oral cancer. COAT is a novel imaging modality capable of detecting profiles of wide-band ultrasonic transients at the site of pulsed laser irradiation. Animal model of oral cancer used Syrian golden hamsters treated with carcinogenic agent, DMBA (9,10-Dimethyl-1,2-Benzanthracene). Opto-acoustic tomography was applied to visualize the course of cancer development from normal to displasia, to carcinoma in situ, to invasive carcinoma. Correlation of the opto-acoustic images with H&E histology sections confirmed that early cancer lesions, invisible by gross observation, could be detected with the opto-acoustic tomography. Our hypothesis is that pronounced contrast revealed by the opto-acoustic tomography between normal and malignant tissues is associated with increased sizes and concentration of cellular nuclei at the stage of microscopic displasia and with tumor angiogenesis at the later stages. Characteristic feature of carcinoma progression as demonstrated by COAT is the gradual loss of layered structure in mucous and developing heterogeneity.
Time Resolved Photon Migration Tomography with a Novel Remote Ultra Low Light Imager (RULLI)
Authors: George John S. , Rector David M. , Ho Cheng , Albright Kevin , Smith Clayton , Hielscher Andreas H.
Published: February 2023

We describe the design and initial applications of an instrument for time and spatially resolved photon migration tomography. The remote ultra low light imager (RULLI) records photon X, and Y positions, and time with <20 ps resolution. Placing the RULLI detector on one side of a scattering object, and illuminating the other side, measures the time history, amplitude, and positions of photons traveling through the object. Another configuration uses a fiber optic collecting array with elements placed at many locations surrounding the object. Spatial and temporal patterns of photon arrival are recorded from multiple source locations around the object, allowing reconstruction of optical properties of the medium.
Modulation transfer function variation through anisotropic turbulence in biological tissue
Authors: Ata Yalçın , Gökçe Muhsın Caner , Baykal Yahya
Published: February 2023

Analysis of the long-exposure modulation transfer function (MTF) is performed for optical imaging using plane and spherical waves through anisotropic turbulence in biological tissues. To obtain the MTF, the wave structure functions of plane and spherical waves are obtained in closed-form expressions. Results are presented depending on various parameters of the turbulent medium and optical beam. The positive effect of anisotropy on optical imaging is remarkable in turbulent biological tissues. Besides scattering and absorption, taking anisotropy into account as well as turbulence will lead to a more accurate description of the performance of the medical imaging systems that use optical spectrums in biological tissues.
Identification of Bacterial Pathogens by Laser Excited Fluorescence
Authors: Lytle Fred E.
Published: February 2023

Aminopeptidase profiling is an established bioanalytical technique used for the identification of bacterial pathogens. This method is based on the production of highly fluorescent β-naphthylamine (BNA) through aminopeptidase hydrolysis of a series of nonfluorescent L-aminoacid-β-naphthylamide substrates by the microorganism of interest. The resultant profiles used to make the identification are bar graphs of the extent of hydrolysis of the substrate versus the identity of the nutrient. The shape of the plot is indicative of the pathogen.
Low-Temperature and Fragmentation Methods in Analytical Molecular Fluorescence Spectrometry
Authors: Wehry E. L.
Published: February 2023

Molecular fluorescence spectrometry is widely used in chemical analysis for several reasons, including (a) the ability to achieve very low limits of detection for intensely fluorescent analytes; (b) its capabilities for remote detection (e.g., by laser and/or fiber optic probe techniques), and (c) acquisition of information useful for molecular identification (excitation and emission spectra; decay times; polarization).
CARS Diagnostics for Applied Combustion Research
Authors: Eckbreth Alan C.
Published: February 2023

The application of laser spectroscopy to the hostile, yet easily perturbed, environments of practical combustion devices is anticipated to afford considerable advances in combustion technology in the coming years. Of various laser approaches, coherent anti-Stokes Raman spectroscopy (CARS) appears to be the most promising approach for the remote, spatially and temporally precise measurement of temperature and major species in practical combustion systems. Over the last several years, the development of CARS has progressed from simple flames of increasing complexity to practical application in afterburning jet engines, internal combustion engines, furnaces and a myriad of other devices. Considerable effort has been expended over this period to extend the capabilities and applicability of CARS, e.g. to higher pressures, to more particle laden systems, etc. In this presentation, recent research activities in our laboratory along these lines will be discussed.
Refractive Index Detector Based on Two-Wave Mixing in Photorefractive Materials*
Authors: Nolan Thomas G. , Ramsey J. Michael , Whitten William B.
Published: February 2023

When two coherent beams of identical frequency intersect they interfere with one another, creating a stationary intensity pattern. This interference pattern will have planes of constant phase at an angle which bisects the two crossing beams. The spatial position of the intensity maxima depends upon the relative phase of the two interacting beams. When these two beams cross in a photorefractive material, photoinduced charges migrate or diffuse from high-intensity regions to low-intensity regions. The resultant spatial modulation of the charge density produces a spatially varying electric field. The electric field then produces a refractive index grating through the linear electrooptical effect. Because the electric field depends on the gradient of the electric potential, the resultant index grating is phase shifted from the interference pattern by π/2. The result of the non-local index grating is an isotropic scattering of the two incoming beams off of this grating. The net result is the coupling of energy out of one beam into the other. Provided the gain-length product for the coupling phenomenon is sufficiently large, essentially all of the energy is coupled into one beam while the other beam is extinguished. This two-wave mixing process can be understood by looking at the relative phase shift of the scattered light relative to the original laser beams.
Laser-Induced Photoconductivity in Polynuclear Aromatic and Carotenoid Thin Films
Authors: Tierney Michael , Lubman David
Published: February 2023

Photoconductivity in polynuclear aromatic hydrocarbons and straight-chained polyenes has been known for some time.1, 2 At room temperature and in the dark these compounds are all insulators; however, under the illumination of a bright light source (e.g., a laser), they become semiconductors. Polynuclear aromatics have been investigated as likely photoconductors because of their molecular geometry and electronic structure. The planar molecules crystallize so that some interaction between the pi-orbitals in the rings of adjacent molecules occurs. Charge carriers therefore can hop between adjacent molecules via the pi-orbitals. Straight chain polyenes, such as beta-carotene, are also photoconductors because of their geometries. The long conjugated backbone allows conduction of charge carriers along its length. The photoconductive behavior of carotenoids is believed to be involved in photosynthesis and vision. The light sources used in early studies were flashlamps or tungsten filament lamps and the currents produced were very small, i.e. on the order of picoamperes.
Low-Pressure Laser Spectroscopy with Flame Atomization
Authors: Whitten W. B. , Koutny L. B. , Nolan T. G. , Ramsey J. M.
Published: February 2023

The air-acetylene burner is commonly used as an atomization source for elemental analysis with various spectroscopic methods, ranging from flame emission to sophisticated laser-based techniques. The latter include laser-induced fluorescence, laser-enhanced ionization, polarization saturation spectroscopy, and degenerate four-wave mixing. All of these techniques exhibit excellent sensitivity for trace elements in water, typically in the parts per billion range or better. The spectral resolution, however, is limited to about 5 GHz because the spectral lines are broadened by collisions in the atmospheric pressure flame. We have developed a low-pressure interface that allows a hundred-fold improvement in resolution while retaining the sensitivity and convenience of flame atomization. We have tested the apparatus by studying the spectrum of the sodium D lines, using a type of saturation spectroscopy. We have been able to separate hyperfine transitions and crossover resonances with a resolution of better than 50 MHz. A recognizable hyperfine spectrum can be obtained with as little as 100 ppb of sodium.
Trace Analysis of Solids Using Multiphoton Resonance Ionization
Authors: Pappas D. , Hrubowchok D. , Mitchell L. , Winograd N.
Published: February 2023

Energetic ion bombardment has been coupled with Multiphoton Resonance Ionization Spectroscopy to yield a powerful tool for surface analysis. This technique will be used to search for and examine he double-beta decay of Xe to Ba.
New Imaging Technique Using Acousto-Optic Deflectors for Mapping of Transient Events
Authors: Yappert M. C. , Huie C. W. , Kimbrell S. M. , Yeung E. S.
Published: February 2023

The ability to scan acousto-optic deflectors very rapidly (105 -106 Hz), while maintaining spatial resolution makes it possible to obtain frozen one or two dimensional images at different times during the evolution of a single event, such as atomic or molecular populations in a laser generated plume.
A Fiber-Optic Two-Photon Combination for Real Time Analysis in a Factory Setting
Authors: Steffen Ray L. , Lytle Fred E.
Published: February 2023

The use of optical fibers as chemical sensors is becoming increasingly widespread and diverse, ranging from probes for determining enzyme activities to detecting contaminates in underground water. Of particular interest to this research group is the area of fiber optic fluorosensing. Typically, the probe is a bifurcated fiber bundle, where part of the bundle is used to transport the excitation radiation to the sample, and the remaining fibers deliver the emission to the detector. The common end of the bundle is placed in the sampling environment. Alternatively, a fiber fluorosensor can be simply a single fiber, serving both transportation and collection purposes.
Spectrochemical Analysis Using Degenerate Four Wave Mixing
Authors: Ramsey J. Michael , Whitten William B.
Published: February 2023

Degenerate four-wave mixing, or DFWM, has been shown to have considerable potential as a technique for optical spectrometry (1)(2). Spectral resolution comparable to the natural linewidth can be obtained for atomic vapor samples due to the Doppler free nature of the measurements. To our knowledge, however, the applicability of the DFWM technique to trace elemental analysis has not been explored. Pender and Hesselink (3) have shown that DFWM can take place in an air-acetylene flame with sodium from an aspirated aqueous solution as the sample. However, they were attempting to show that DFWM could be used as a combustion diagnostic tool and involved measurements at relatively high concentrations. In this talk we will present the results of a study of degenerate four-wave mixing in atomic sodium produced in an analytical flame.
Balloon-Borne Remote Laser Induced Fluorescence Measurements of Hydroxyl Radical in the Stratosphere
Authors: McGee Thomas J. , Heaps William S.
Published: February 2023

A balloon-borne instrument designed to measure hydroxyl radical (OH) in the stratosphere has been successfully flown four times in the last three years. Data from these flights have resulted in measurements from ~22 - 38 km. These measurements represent the only measurements made to date of OH below 30 km.
The Use of cw Lasers in Resonance Ionization Mass Spectrometry
Authors: Parent Denise C. , Keller Richard A. , Miller Charles M.
Published: February 2023

Resonance ionization mass spectrometry (RIMS) was developed as an analytical tool using pulsed lasers and element selective ionization.1 We have demonstrated recently that the 100% duty cycle of cw lasers results in a larger ionization efficiency for Lu relative to the use of pulsed lasers.2 However, it was necessary to tightly focus the cw laser, leading to poor sample utilization and power broadening of the resonant transition. We are ultimately interested in high efficiency, isotope selective ionization. In this paper we present the results of combining a low irradiance tunable laser to provide selectivity without power broadening, with a high irradiance argon ion laser to provide efficient ionization over large volumes. Progress towards Doppler-free excitation will also be discussed.
Differential Thermooptic Spectroscopy Using the Two-Frequency, Zeeman Effect Laser
Authors: Johnston Roger G.
Published: February 2023

Differential thermooptic spectroscopy [1,2] involves measuring small differences in the optical absorption of two samples. When exposed to incident light, the two samples will be differentially heated due to their differing absorption efficiencies. Such heating differences will cause a change in their relative indices of refraction. This change can be precisely measured using interferometry [1-4].
Tunable Diode Lasers for Resonance Ionization Mass Spectrometry and Very High Resolution Atomic Spectroscopy
Authors: Shaw R. W. , Young J. P. , Smith D. H.
Published: February 2023

Many tunable laser-based analytical techniques developed over the past decade have remained research curiosities. The sensitivity and selectivity limits that have been demonstrated using these techniques are impressive. The lasers required for their implementation, however, are either too expensive or too complicated for routine settings. The advent of inexpensive, simple GaAlAs diode lasers offers the hope that this situation can be improved. These devices emit in the near infrared spectral region (670 - 850 nm) at typical powers of 5 to 30 mW. They generate coherent output beams and are tunable either by temperature or drive current control. Single longitudinal mode operation is standard for off-the-shelf, index-guided devices, and linewidths can be as narrow as a few tens of megahertz without any external cavity arrangement. An entire laser source (including laser and mount, temperature controller, and current supply) can be assembled from commercial components for less than $5000.
Laser Photoionization in an Ion Trap Mass Spectrometer
Authors: Goeringer D. E. , Whitten W. B. , Ramsey J. M.
Published: February 2023

The use of three dimensional quadrupole electrodynamic traps for conventional mass spectrometry and for MS/MS experiments has become popular since their commercial introduction by Finnigan. The development of the mass selective instability mode of scanning these devices to generate a mass spectrum is largely responsible for their popularity. This mode of operation allows ions with a broad range of m/e values to be stored in the trap. Ions can then be sequentially ejected from the trap (from low to high m/e) as the RF voltage is increased. The ejected ions are detected with high sensitivity by an electron multiplier.
Optical Emission Spectrometry and Laser Induced Fluorescence Spectrometry of Laser Produced Sample Plumes
Authors: Niemax Kay
Published: February 2023

The experimental investigations of the ablation and atomization process of solid samples by pulsed laser radiation were performed with an arrangement shown in Fig. 1. A Nd:YAG laser of excellent mode profile and power stability working at its fundamental wavelength was used for ablation. Metallic samples of good homogeneities were placed in a vacuum-tight vessel which could be filled with buffer gas (Ar). In order to excited analytes selectively in the plasma plume produced by the Nd:YAG laser, the beam of a pulsed dye laser was sent into the microplasma with a preselected delay. Radiation from the plasma as well as the fluorescence transitions were detected with a sensitized, gatable optical multichannel analyser adapted to a medium-resolution spectrograph.
An Intercomparison of the NASA/GSFC Stratospheric Ozone Lidar with Rocoz Sondes and Microwave Measurements
Authors: McGee T. J. , Ferrare R. , Burris J. , Connor B. , Barnes R. , Butler J. , Whiteman D. , Parrish A. , Torres A.
Published: February 2023

NASA Goddard's Stratospheric Ozone Lidar Trailer Experiment (STROZ LITE) was deployed at JPL's Table Mountain Facility (34.4N, 111.7W) during July 1989 for the purpose of intercomparing with other types of ozone sensors. This paper discusses some of the Goddard results and compares them with a new microwave instrument (co-located at Table Mountain), and with in-situ measurements of ozone from rocket-borne sondes (launched from San Nicholas Is., about 100 miles west of Table Mountain).
Construction of a Resonance Ionization ToF Spectrometer with a Filament heated Tantalum Furnace
Authors: Bengtsson Lars
Published: February 2023

Common mass spectrometry utilizing non-selective ionizationprocesses, like electron bombardment, has an excellent isotopic selectivity, but is unable to distinguish different isobars. For example, the 90Sr signal would interfere with the 90Rb signal in a mass spectrometer based on electron impact ionization. The introduction of tuneable dyelasers in the mid 70's made it possible to selectively excite and/or ionize free atoms. A method based on resonance excitation of atoms, laser enhanced ionization (LEI), have been developed and used for trace element analysis in flames (1) and recently also in atmospheric pressure graphite furnaces (2). Sensitivities in the ppb and even in the subppb range have been reported for many elements. The selective excitation of the atoms eliminate the isobaric interferences confronted in mass spectrometry, but unless a very narrow band-width laser is used, the method will suffer from an unability of distinguishing different isotopes. For example 90Sr can not be distinguished from 91Sr or 92Sr in LEI.
Detection of Transient and Stable Species in Low Pressure Flames
Authors: Sausa R.C. , Locke R.J. , Howard S.L. , Forch B.E. , Miziolek A.W. , Bernstein J.S. , Cool T.A.
Published: February 2023

Profiles of major and minor species in low pressure flames are needed to better understand the chemistry occuring in flames and to validate existing chemical kinetic flame models.
Optimization of a Photoacoustic Cell Using a Finite Difference Model
Authors: Schurig D.A. , Russo R.E. , Silva R.J.
Published: February 2023

Photoacoustic spectrometers, for high-sensitivity solution absorption measurements, have been set up using pulsed laser illumination of cuvettes with piezoelectric transducers and gating amplifiers1. Such systems can attain higher sensitivity if the systems’ parameters are optimized and a few modifications are made. We developed and tested a model for describing the photoacoustic energy generation, propagation, and detection.
Laser In-Situ Monitoring Of Combustion Processes
Authors: Wolfrum J.
Published: February 2023

In recent years various methods have been developed for non-intrusive observation of complex chemical reaction such as combustion processes.
Photon Migration in Biological Tissue
Authors: Nossal Ralph
Published: February 2023

In recent years considerable effort has been given to developing noninvasive diagnostic procedures which utilize light to penetrate optically turbid biological tissues. Among these are pulse oximetry1,2 and time-resolved absorption spectroscopy3–5 to assess regional blood oxygenation, laser Doppler techniques to measure peripheral blood flow,6 and imaging modalities to discern tumours or other tissue inhomogenities.7–9 These methods, which are directed towards the analysis of living tissues, rely upon photons which have migrated through a highly scattering tissue matrix before being re-emitted and detected at an accessible surface.
Spectroscopic Measurements on Single Molecules in Solution
Authors: Shera E. Brooks , Soper Steven A. , Davis Lloyd M.
Published: February 2023

The detection of single atoms in the gas phase was first accomplished in 19771 and the detection of single molecules in a solid matrix at low temperatures in 1989.2 The detection of single chromophore molecules in aqueous solution presents different problems and has only recently been achieved.3 Because of the many applications of ultrasensitive detection in liquid environments, the sensitivity obtained using fluorescence detection has had a long history of incremental improvements. A new urgency came to the field when it was suggested that DNA may be sequenced at rates many times that of current methods by sequential enzymatic cleavage of an appropriately labeled single DNA strand followed by detection and identification of the individual labelled nucleotides.4
Orientation and Picosecond Reorientation at Interfaces
Authors: Wirth Mary J. , Burbage John D.
Published: February 2023

The orientational dynamics of a surfactant at both liquid/solid and liquid/liquid interfaces are characterized and compared. Acridine orange, a fluorophor, accumulates at water/hydrocarbon interfaces. Using fluorescence anisotropy measurements, the orientational relaxation is characterized with resolution on the picosecond time scale. At the interface of water and a monolayer of C18 alkyl chains, the molecules reorients in-plane in 0.4 ns, with little hindered rotation. The molecule is strongly hindered from out-of-plane rotations: it is restricted to orientations within ±13° of the plane of the surface. Small amounts of alcohol widen the distribution to ±20°. At the interface of water and n-hexadecane, which is a liquid at room temperature, the in-plane reorientation is slightly faster: 0.3 ns, and it is unhindered. Compared to the liquid/surface interface, the molecule is even strongly hindered from out-of-plane orientation: it is restricted to only ±4° of the plane of the interface. The interpretation is that the surface of water is much smoother in contact with the hydrocarbon liquid than it is with the hydrocarbon monolayer. The effect of alcohols on the smoothness of the water/hexadecane interface is being investigated experimentally.
Laser Applications of Vibrational Spectroscopy to Mineral and Coal Processing
Authors: Young C. A. , Yu Q. , Knutson K. , Miller J. D.
Published: February 2023

The spectroscopic analysis of mineral and coal samples from various process operations has received much attention worldwide. Our research group is presently using four vibrational spectroscopic techniques for the in-situ characterization of these samples and their surfaces. These techniques involve Fourier-transform infrared (FT-IR), Fourier-transform Raman (FT- Raman), low-intensity Raman (LIRS), and scanning fluorescence (SFS) spectroscopies, each of which incorporate lasers for interferometry and/or sample excitation purposes. The fundamentals behind each of these techniques are reviewed, thereby demonstrating why lasers are necessary. Finally, experimental results are presented which describe the surface chemistry of coal/resin flotation systems and the adsorption phenomena/double-bond reactivity of unsaturated fatty acids at semisoluble salt mineral surfaces.
OH detection and spectroscopy by DFWM in flames; comparison with CARS
Authors: Bervas H. , Taran J. P. , Le Boiteux S.
Published: February 2023

OH detection by degenerate four-wave mixing in a Ch4-air flame is performed, and a comparison between CARS and DFWM is given.
Laser-Induced Fluorescence and Stimulated Emission in Combustion Diagnostics
Authors: Westblom Ulf
Published: February 2023

Results from investigations of the effects of photo-chemical processes and stimulated emission on laser-induced fluorescence are discussed in the context of combustion diagnostics.
One Molecule Detection by Laser Induced Fluorescence of Levitated Microdroplets
Authors: Whitten W. B. , Ramsey J. M. , Ng K.C. , Arnold S.
Published: February 2023

The extreme sensitivity of fluorescence spectrophotometry results from the fact that a molecule can undergo many excitation-emission cycles before destruction by photochemical degradation. For example, Rhodamine 6G (R6G) can emit in excess of 105 photons before photolysis takes place1. The fraction of emitted photons collected and converted to countable pulses can be as high as 10-3, although 10-4 is more readily attainable. Therefore, sufficient signal exists for single molecules to be detectable. Detection limits for molecules in solution have been limited by background signal from solvent Raman scattering and fluorescence. This background signal adds noise to the measurement and has effectively restricted the detectable concentration to about 10-13 M. Over the past decade, advances in detection of fewer molecules have all been made by reducing the measurement volume and/or increasing the measuring time. Given the above concentration detection limit a reduction of the measurement volume to 1 pL leads to a minimum observable quantity of ≈1 molecule. The ability to detect a single molecule in condensed phase could have many important applications in addition to being an interesting problem. The obvious application of this approach is to situations where small quantities of material are available for analysis. The capability to reliably detect a single fluorophore might also allow the screening and/or sorting of a collection of molecules. Such abilities would have application to many biological problems such as DNA sequencing and detection of DNA adducts.
Application Specific Semiconductor Lasers in sensor systems for chemical analysis
Authors: Höjer Svante , Ahlberg Henrik , Broberg Björn
Published: February 2023

Measurement methods based on laser spectroscopic techniques have always been a very attractive solution for chemical analysis of gaseous compounds due to well known properties like high selectivity, high sensitivity, and an inherent resistance to interference effects from other gases. Laser systems for real-time monitoring of gases have been used in a number of different applications. Emission control of diffuse leakages from petrochemical plants [1] and measurements of pollutants in urban areas [2] have successfully been performed. However, due to a high degree of complexity where well trained personnel is necessary these systems are ordinarily related with high costs and therefore its use are often limited to research establishments.
Elemental Analysis of Actinide Compounds / Materials Via the Optical Emission from Laser-Initiated Microplasmas
Authors: Barefleld J.E. , Dyer R.B. , Ferran M.D.
Published: February 2023

The purpose of this work is to develop real-time in situ capabilities for monitoring actinide (particularly plutonium and americium) concentrations in molten salt media. In this report, we discuss the state of the art Laser-Induced Atomic Emission (LIAE) apparatus which we have developed and report survey atomic emission spectra for solid samples of PuC13, AmO2, PuO2, and SRL waste glass.
Atmospheric Multi-Component Pollution Analysis Using CO2 Laser
Authors: Rob Mohammad A. , Franceschetti Frank C.
Published: February 2023

The laser spectroscopic techniques for detecting minor gaseous pollutants of the atmosphere have made rapid advances in the last few years. The most important optical process for detection of air pollutants is based on the extinction of radiation by molecular absorption. Each molecule absorbs light at a particular wavelength or a range of wavelengths, a characteristic of the molecule. Thus a measurement of absorption of light at the molecule's characteristic wavelength produces a mean of determining a particular molecule at the presence of other molecules. Problems can, and often arise from overlapping spectrums due to other molecules of the atmosphere. In this case, it is necessary to identify the molecules which cause these overlappings. In some cases, one might be interested in finding multiple pollutants of the atmosphere.
Tunable Diode Laser Study of Premixed Methane/Oxygen Flames Inhibited by Halogenated Compounds
Authors: Daniel Robert G. , McNesby Kevin L. , Miziolek Andrzej W.
Published: February 2023

We are presently conducting experiments in which we obtain both temperature and species concentration profiles of a low pressure, premixed methane/oxygen flame, to which small amounts (0.25 -1.0 %) of a halogenated methane compound have been added. We are using the method of Two Line Thermometry [1], in which a pair of IR active transitions are recorded by tunable diode laser (TDL) absorption spectroscopy and analyzed to determine the temperature of the flame and the partial pressure of the absorbing species. This method offers a nonperturbing probe of flame characteristics and has the abilitiy to operate over a broad range of elevated temperatures. TDL absorption spectroscopy can be used wherever a line-of-sight configuration is possible and background gas absorptions do not interfere.
Laser-Induced Fluorescence Measurements of CH and C2 During Diamond CVD
Authors: Raiche George A. , Brown Michael S. , Jeffries Jay B.
Published: February 2023

Chemical vapor deposition (CVD) of diamond film has recently been discovered in variety of flame and plasma environments. A gas jet of effluent from a dc-arc plasma has one of the fastest growth rates for high quality diamond film. To improve the yield from such arc-jet plasmas, models of the deposition chemistry and sensors to control the reactive gas jets are needed. Measurements of the gas temperature in the jet and boundary layer above the substrate surface are crucial to develop models of the process chemistry. Laser-induced fluorescence (LIF) measurements of the rotational distribution of diatomic radicals has proven an effective method for non-intrusive determinations of gas temperature in low-pressure flames.1 In this presentation we discuss LIF observations of CH radicals in a dc-arc-jet reactor during diamond CVD and explore different excitation and detection strategies to determine the optimum method for temperature measurements.
Degenerate Four-Wave Mixing for Quantitative Diagnostic Measurements
Authors: Farrow R. L. , Paul P. H. , Friedman-Hill E. J. , Danehy P. M.
Published: February 2023

We report theoretical and experimental studies of the effects of collisional quenching and the contributions of thermal gratings in degenerate four-wave mixing (DFWM).1 Using single-mode laser radiation, peak signal intensity measurements were performed on an isolated line in the A-X transition of NO. By using appropriate mixtures of N2 and CO2 as buffer gases, we varied the collisional quenching rate over several orders of magnitude while maintaining a fixed total collisional dephasing rate. The varying quenching rate also had the effect of varying the heat released by population gratings to form thermal gratings, permitting detailed comparisons of signal intensities from both mechanisms.
Effects of Doppler Broadening and Unequal Pump Intensities in Saturated Degenerate Four-Wave Mixing Spectroscopy
Authors: Lucht Robert P. , Brown Michael S. , Rahn Larry A.
Published: February 2023

Degenerate four-wave mixing (DFWM) is a technique that shows great promise for sensitive measurements of transient gas-phase species, and diagnostic applications of DFWM are being pursued actively at laboratories throughout the world. Applications of DFWM as a combustion diagnostic and as a tool for molecular spectroscopy are reviewed in a recent article by Farrow and Rakestraw (1992). However, significant questions remain regarding strategies for quantitative concentration measurements using DFWM.
Mass Spectrometry of Individual Microparticles in an Ion Trap
Authors: Ramsey J. M. , Dale J. M. , Yang M. , Whitten W. B.
Published: February 2023

The characterization of individual microparticles has become more important recently with the increasing need for meteorological, environmental, medical, and intelligence data (1). Early attempts at on-line analysis used a heated filament to evaporate a portion of the particulate sample. Ionization in some cases occurred on contact, in other experiments, a supplemental electron beam was employed. Off-line measurements on individual particles have been made by laser microprobe analysis, SIMS, and by optical measurements (1). There have been several recent reports of online single particle measurements with pulsed laser desorption and ionization with time-of-flight mass spectrometry (2-4).
Time-resolved Thermometry in a Condensing Laser-ablated Copper Plasma Plume by Doppler-resolved Laser Induced Fluorescence
Authors: Zerkle David K. , Sappey Andrew D.
Published: February 2023

Doppler-resolved laser-induced fluorescence (LIF) excitation scans of the Cu atom ground state are used for thermometry in laser-ablated plasma plumes. The resulting LIF line shape is analyzed by fitting Voigt profiles to determine the Doppler width of the transition which then yields directly, translational temperature. Temperature is an extremely important parameter in determining the rate and extent of condensation occurring in metal vapor plumes such as the copper plumes which we have been studying. The other seminal controlling parameter, density, has been determined using a combination of hook spectroscopy and planar laser-induced fluorescence (PLIF) as described in several preceding papers1,2 and a newer, more extensive study which is to be published3. In this work, the plume is produced by excimer laser bombardment of an OFC copper target rotating in a vacuum chamber (308 nm, > 20 J/cm2, 1-5 GW/cm2). The copper plasma plume expands rapidly into a helium or argon background gas at pressures of 1 and 10 torr. Scans with 25 torr of background gas yield no useful data as a result of various broadening mechanisms which make fitting unique Voigt profiles difficult. We find that plumes expanding into argon are kinetically hotter and cool more slowly than those in helium. For example, temperatures in 1 torr of helium and delay times between the ablation and probe pulses of 0.5, 1.0 and 3.0 msec are 1800 ± 250 K, 1600 ± 200 K, and 1300 ± 150 K , while temperatures in 1.0 torr of argon for identical delays are 3900 ± 700 K, 3000 ±350 K, and 2600 ± 250 K. In 10 torr of helium, the temperatures are 300 ± 150 K, 300 ± 300 K, and 300 ± 300 K for delays of 0.2, 0.5, and 1.0 msec; whereas temperatures for the identical delay times in argon background gas at 10 torr are 2000 ± 350 K, 1600 ± 200 K, and 1000 ± 100 K. This result helps to explain our earlier observation that the rate of disappearance of Cu atom due to condensation reactions in these plumes is faster in helium than in argon as well as the more general observation that forming clusters and particulate in argon is not as easy as in helium3,4. Physically, this likely results from the higher thermal conductivity of helium relative to argon making helium better suited at removing the excess heat from the plume.
Phase-Sensitive Flow Cytometry: New Technology For Analyzing Biochemical, Functional, and Structural Features in Fluorochrome-Labeled Cells/Particles
Authors: Steinkamp John A.
Published: February 2023

Flow cytometry (FCM) instruments rapidly measure biochemical, functional, and cytological properties of individual cells and macromolecular components, e.g., chromosomes, for clinical diagnostic medicine and biomedical and environmental research applications. These measurements are based on labeling cells with multiple fluorochromes for correlated analysis of macromolecules, such as, DNA, RNA, protein, and cell-surface receptors. In addition to utilizing the spectral emission properties of fluorescent markers, i.e., different colors/intensities, to measure specific cellular features, the excited state lifetimes also can provide a means to discriminate among the different fluorochromes. A new FCM approach, based on phase-resolved fluorescence lifetime spectroscopy methods (Vesoelova et al, 1970, Lakowicz and Cherek, 1981), recently has been developed to provide unique capabilities for separating signals from multiple overlapping emissions in fluorochrome-labeled cells as they pass across a modulated laser excitation source (Steinkamp and Crissman, 1993). In addition, the measurement of fluorescence lifetime (Pinsky et al, 1993, Steinkamp et al, 1993) also is of importance because it provides information about fluorophore/cell interactions. An important advantage of lifetime measurements is that lifetimes in some case can be considered as absolute quantities. However, the lifetime of fluorophores bound to cellular macromolecules can be influenced by physical and chemical factors near the binding site, such as solvent polarity, cations, pH, energy transfer, excited-state reactions, and quenching. Thus, lifetime measurements can be used to probe the cellular environment, possibly including chemical and structure changes that occur in DNA and chromatin. Table I lists the lifetimes of some typical fluorochromes that are used to quantify cellular DNA, total protein, and antibody-labeling to cellular antigens.
Single-Molecule Detection in Microdroplets
Authors: Barnes Michael D. , Whitten William B. , Ramsey J. Michael
Published: February 2023

Detection of single molecules in condensed phase with high signal-to-noise ratios is important for applications which involve detection of fluorescent tags such as DNA sequencing1, fluorescence immunoassay2, or hydrology.3 In addition, observation of photophysical phenomena unique to the interaction of a radiation field with an isolatedmolecule, such as photon antibunching,4 depends upon having such high sensitivity. As demonstrated by the experiments of Moerner5 and Orrit,6 very high sensitivity at the single molecule level can be achieved by probing "guest" molecules in solid hosts at cryogenic temperatures. However, practical applications requiring single molecule detection usually require measurements on liquid phase solutions at room temperature. These demands pose new problems such as solvent dependent quantum yield, finite photochemical lifetime (the number of absorption-emission cycles which occur before irreversible bleaching of fluorescence), and solvent Raman scattering and fluorescence.
Surface Chemical Analysis on Diamond C(111) by IR Sum Frequency Generation and Second Harmonic Generation Spectroscopy
Authors: Chin R.P. , Huang J.Y. , Shen Y.R. , Chuang T.J. , Seki H.
Published: February 2023

Infrared sum frequency generation (SFG) and second harmonic generation (SHG) has found widespread use as surface sensitive probes [1]. As second order nonlinear processes, SFG and SHG are forbidden in the bulk of centrosymmetric media but allowed at its interface where the symmetry is broken. We have used the techniques to study adsorption of H and CHX on diamond. In particular, with the help of a tunable infrared laser, the infrared-visible SFG allows us to measure in-situ surface vibrational spectra and hence identify the adsorbed species. The results provide us with useful insight about possible mechanisms governing the chemical vapor deposition (CVD) process for diamond growth.
Detection of Chlorine and Oxygen in a Microwave-Induced Plasma Using Frequency Modulation Spectroscopy
Authors: Chien Ring-Ling
Published: February 2023

Frequency modulation spectroscopy (FMS) in the wavelength range 700-1500 nm, is becoming increasingly important as an analytical technique for two reasons. One is the rapid development of diode lasers and the other is the improvement in detector technologies. Near-infrared diode lasers are inexpensive, reliable, and readily available. Line-locked wavelength modulation with second-harmonic (2f) detection using these diode lasers has been demonstrated to be a sensitive and accurate absorption technique.1 This technique is ideal for small molecules such as H2O, HCl, CO, and CO2. By locking the wavelength to the molecular line of interest, the technique is well suited for continue and real-time monitoring applications as in gas chromatography (GC).
C2 Swan Band Spectral Measurements of Temperatures in a Decaying Laser-Induced Plasma
Authors: Parigger Christian , Plemmons David H. , Hornkohl James O. , Lewis J. W. L.
Published: February 2023

It is of interest to characterize temperature fields from laser-induced breakdown plasmas in a temporal regime well separated from the breakdown initiating laser pulse. The post-breakdown emission spectra are predominantly recombination molecular spectra. The use of such spectra has been previously demonstrated to yield high temperatures for CN.1