bluuebunny/crossref_metadata_2025 huggingface dataset:
Holographic Data Storage using Thick Bacteriorhodopsin Recording Materials
Authors: Smithey D. T. , Babcock W. C. , Millerd James
Published: February 2023

Current holographic data-storage (HDS) technologies have not been commercially developed due in part to the lack of an optical-recording material with appropriate characteristics. The ideal optical-recording material would have high resolution, high sensitivity (for both recording and erasure), high photochemical and thermal stability, optical erasability, permanent storage capability, and read-without-erasure capability (Sincerbox, 1995).
Viterbi Decoding Circuit for DVD Players
Authors: Hayashi H. , Umezawa M. , Kobayashi H.
Published: February 2023

The DVD has the highest recording density in the optical discs of practical use. From such a high density medium, it is difficult to reproduce digital data accurately. We coped with this by developing a Viterbi decoding circuit for DVD players. In the following, we will outline the structure and the efficiency of the Viterbi decoder.
3.5 inch Drive Technology(HS) by Magnetic Field Modulation
Authors: Watanabe Tetsu
Published: February 2023

A high performance 3.5 inch magneto-optical disk drive that stores 650 mega Bytes user capacity is developed and commercialized. Laser Strobe Magnetic Over-lop recording technology is employed. Thinner disk with 0.8mm thick substrate in a cartridge with a dimension 5x92x97 mm is introduce. The highest area density 1.3 Giga bits per inch2 is achieved.
Real-time nonresonant and erasable holographic memories using an acceptor-donor azo-dye-polymer film
Authors: Bao Xinxian , Hou Ming , Li Chunfei
Published: February 2023

Photosensitive organic materials are showing promise as versatile candidates in the filed of information storage due to their special advantages: low cost, easy to handle, real-time recording capabilities, fast response time, wide frequency band and large third-order nonlinear susceptibility. The experiments were mainly focused on the resonant absorption region of materials because the resonant light may enhance the third-order nonlinear susceptibility and storage capability. In this paper, we report the experimental results of nonresonant real-time holographic memories on a azo-dye doped polymer (ADP) film. The ADP film shows quite large nonresonant third-order nonlinearity and real-time polarization holographic memories properties.
Optical Diffractive Storage
Authors: Ramenah H. , Bertrand P. , Soubari. E.H. , Meyrueis P.
Published: February 2023

Gratings are recorded in dichromated gelatin and diffraction efficiency uniformity of each 20 angularly multiplexes is showed. Energy coupling between gratings is studied and illustrated.
Real-time Staging on Optical Disk Library
Authors: Mizukami Makoto , Iwatsu Shigetaro , Izawa Nobuyoshi
Published: February 2023

In an optical library system [1], since the disks that have recently been used are often likely to be used again shortly thereafter, the presence of disks stored near the disk drive increases the overall speed of the system (Fig. 1). The movement of disks from a relatively far cell to a relatively close cell is known as "staging". In real-time staging, the disks are staged through the conventional read/write process between the storage cells and the disk drive to permit rapid access to the disks as required in the future.
Near Field Optical Technology for High Density Optical Storage and Nano-photonics
Authors: Saiki Toshiharu
Published: February 2023

Near-field optical excitation with apertured optical fiber has been utilized to realize the high density data storage with spot sizes beyond the diffraction limit. So far, magneto-optical-mode storage on a Co/Pt film [1] and optical-mode one on the LB film of amphiphilic azobenzene derivative [2] have been reported. Recently, with regard to the latter technique, much smaller pit sizes are successfully achieved by using a nanometric aperture. In order to increase the write speed, high excitation density through the aperture is required. For this purpose, we optimize the shape of fiber probe for attaining high transmission efficiency of light. Its ability in the application to nano-photonic devices is also demonstrated through the spatially resolved spectroscopy of novel-structured semiconductor devices.
3-D Data Storage in Two-Photon Photochromic Optical Memories
Authors: McCormick F. B. , Cokgor I. , Dvornikov A. S. , Wang M. , Kim N. , Coblentz K. , Esener S. E. , Rentzepis P. M.
Published: February 2023

Rapid increases in the computer processing power available per unit cost, as well as a growing hunger for multimedia (text, audio, and image) entertainment and processing has led to heightened interest in multilayer and other volume optical storage technologies.1 One such technology is 2-photon absorption-based storage.2,3,4 In this approach, writing or erasure takes place only at the intersection of 2 beams of different wavelengths, thus allowing independent addressing of any point within a 3-dimensional volume. As a bit oriented (rather than holographic) memory, a unique physical location is allocated for each data bit. If individual bits are stored, volumetric densities on the order of terabits/cm3 may be achievable, and parallel reading of the bits (e.g.-in planes or pages) can enable 100 Gb/s data transfer rates. The key principle behind 2-photon memories is the creation of a molecular change in the media by the simultaneous absorption of 2 photons from 2 different beams by the dopant molecule, as shown in Fig. 1(a). The localized change can store bits by changing the index of refraction, absorption, fluorescence, or the material’s electrical properties. In our system experiments so far we have utilized materials in which 2-photon excitation creates a new absorption peak and subsequent 1 or 2-photon illumination results in efficient fluorescence for readout. The broad readout absorption profile, and the high fluorescence efficiency enable the use of inexpensive, low power replay sources, including LEDs and filtered lamps. In addition to non-destructive memory recall, we have also demonstrated optically induced erasure, thus enabling random accessibility and erasure of bits. These two-photon 3-D memories are similar to the multilayer optical disk systems with the potential for simple media fabrication, many layers, parallel access for high data transfer rates, and low raw bit error rates (BER). As shown in Fig. 1(b), orthogonal intersection of the writing beams may be used, or if ultra-short (e.g.-<100 femtosecond) pulses are used, a counter-propagating arrangement10,5 is feasible. While single bits may be stored and recalled, parallel access of lines or planes of data is naturally accommodated in two-photon 3-D memories, to provide increased data transfer rates. Due to diffraction of the addressing beam as it propagates across the data image, there exists a tradeoff between the volumetric density of the memory and the parallelism, or data transfer rate.9
Future perspective of Magnetic Super Resolution
Authors: Takahasi A. , Murakami Y. , Hirokane J. , Kurata Y.
Published: February 2023

For high density recording, it is important to record small marks under precise control of mark edges and also to detect them precisely. For example, some proposed methods are magnetic field modulation recording (MFM) with pulsed light, an optical head using a short wave length laser, partial response most likely hood detection (PRML) and a low noise substrate. Especially, the magnetic super resolution (MSR) method is one of the strongest technologies in order to improve readout resolution by the MO media.
Fast vector diffraction calculation for embossed optical disks with arbitrary profiles
Authors: Shimano Takeshi , Kawamoto Kazumi , Umeda Mariko , Nakao Takeshi
Published: February 2023

In the development of future higher density optical disks, it is quite important to determine quickly how the reconstructed signals change according to incident light polarization conditions and the profile shape of the optical disks. Current methods of vector diffraction calculation1-4) for this purpose, however, seem to be possible only when there are several restrictions, such as rectangular profile1-3), one-dimensional profile1), perfect conductive material1-3) or long computation time4). We have tried to offer a solution to this problem in this paper.
Efficient Thermal Modeling of Optical Disk Recording
Authors: Kowarz Marek W.
Published: February 2023

In order to accurately predict mark shapes on recordable optical disks so that write strategies can be more effectively evaluated and optimized, a model for the temperature distribution is required that takes into account heat flow. Thermal modeling is especially important for high-density recording since heat flow effects become more important as mark densities increase. In a few special cases, it is possible to obtain analytical solutions for the temperature in terms of known functions [1-5]. However, for most situations of practical interest, these solutions are not appropriate and some numerical work is required. A precise determination of mark shapes is then time consuming whether one uses semi-analytical solutions that are in integral form [6-12] or purely numerical methods, such as finite differences [13-16] or finite elements [17,18].
Optimum Recording Conditions of Direct Overwrite Magneto-Optical Disk Drive for the Widest Power Margin
Authors: Kurita S. , Saito J. , Ishii K. , Horikawa M. , Akasaka H.
Published: February 2023

In order to achieve a large capacity magneto-optical (MO) disk memory, multi-pulse writing method for accurate control of the locus of the recorded mark edge has been made practical[1]. After the development, 2GB/130mm MO disk memory is now a practicality. Meanwhile, to realize a high data transfer rate in recording, we have already reported the light intensity modulation (LIM) type direct overwrite (DOW) method with the exchange coupled multilayered DOW-MO disk. Also, we have confirmed 2GB/130mm memory is a practicality on the DOW-MO disk[2]. In this paper, we report that using the multi-pulse writing method on DOW-MO disk, optimum MO-drive conditions for the widest power margin have been found.
A New Thermal Response Design for High Recording Density Magneto-Optical Media
Authors: Abiko T. , Konishi A. , Kagawa M. , Igarashi S.
Published: February 2023

Recent magneto-optical ( MO ) disk systems adopt mark length modulation technique in order to improve linear recording density, in which the mark edges have to be recorded more precisely. In light intensity modulation recording MO system such as ISO standardized format, however, recorded marks are deformed because of thermal interference in write process. One of the most effective method to prevent the thermal interference is to use write compensation technique with elaborated write pulse patterns.[1] From this point of view, the thermal response design of recording layer structure must be serious subject in next generation MO disk media. We have investigated new layer structure suitable for higher density format. By means of a computer simulation, it is shown that the thermal response is improved by using a 6 recording layer structure, which has an extra thermal flow control layer. The improvement of recording characteristics is also confirmed experimentally.
Terrain Matching Using Image Sequence Analysis
Authors: Rodríguez Jeffrey J. , Aggarwal J. K.
Published: February 2023

There has been considerable interest recently in the use of digital terrain maps for aircraft avionics systems. Recent advances in the real-time manipulation of digital cartographic databases have led to the development of sophisticated airborne terrain management systems [6]. This capability has sparked renewed interest in digital map-aided navigation.
Shape from Egomotion: A Model-Based Probabilistic Approach
Authors: Hung Yi-Ping , Cooper David B.
Published: February 2023

An important subject in computer vision is to determine 3D scene structure and motion from multiple 2D images taken by one or more, stationary or moving cameras. When there is no relative motion among the objects in view and the camera, and only one fixed camera is available, one tries to extract 3D information using techniques such as shape from shading, or shape from texture. When there is no relative motion, but more than one camera is available, shape from stereo is applicable. Suppose there is relative motion (which may be due to the motion of one or more objects, the motion of the camera, or both), 3D information can be obtained by the techniques generally referred to as shape from motion. If there is motion and more than one camera, one can integrate the information from both the stereo module and the motion module, e.g., [Mit88], [Wax88], Note that stereo problem can be treated as a special case of motion if the spatial distribution of the camera is considered as the result of "instantaneous" camera movement.
Psychophysical and Computational Tests Comparing the Sign-Correlation and Zero-Crossing Models of Human Stereo Vision
Authors: Nishihara H.K.
Published: February 2023

Prazdny[5] introduced a clever wrinkle into the debate on binocular stereo models suggesting that transparent random-dot stereograms would be difficult to solve using just coarse-scale information as would be the case for Marr and Poggio’s zero-crossing theory[1]. These transparent stereograms are, however, relatively easy for human subjects to see. Prazdny proposed an alternate approach which operated on the fine structure in the images.
An Efficient and Accurate Method for Computing Vanishing Points
Authors: Collins Robert T. , Weiss Richard
Published: February 2023

Under perspective projection, parallel lines in three space project to line segments in the image plane which converge to a common point of intersection (perhaps at infinity) called a vanishing point. There are two basic approaches to computing vanishing points from line segments and thereby estimating the surface gradient of a plane assumed to contain the original 3D lines. We will call these the histogram approach and the cross product approach.
Part Description and Segmentation of Range Images by integration of Contour, Surface, and Volumetric Primitives
Authors: Bajcsy Ruzena , Gupta Alok
Published: February 2023

A paradigm for part description and segmentation of range images by integration of contour, surface, and volumetric primitives is proposed. The argument for integration is substantiated by examples.
A proposal for a Real-time Handheld NIR Breast Tumor Imager
Authors: Akin Ata , Pourrezaei Kambiz , Chance Britton
Published: February 2023

Near infrared (NIR) technology using laser light sources at an optical window from 700-900 nm is shown to carry diagnostic value for early detection of breast cancer. The basic principle behind a breast tumor imager depends on detecting the abnormal changes in the optical properties of the breast tissue during cancerogenesis. This imager operates on the well established principle of amplitude cancellation time multiplex system which features congruent images of angiogenesis and hyper-metabolism, two diagnostics for tumors which both may be prognostic as well. The proposed device is a much more compact hand-held, battery operated system that can be used in field studies which is much faster, giving an image every second of the underlying deviation of optical properties of the tumor bearing breast from normal. The image is displayed in real-time on the back of the hand-held optical probe. The imager is a microcontroller controlled, self-calibrating device that requires minimum user interface. It is designed to be operated by technicians.
Quantitative Optical Imaging Using Random Walk Theory
Authors: Chernomordik Victor V. , Hattery David , Gandjbakhche Amir H.
Published: February 2023

The robustness of a random walk model that uses time-dependent contrast functions to quantify the cross-section and the corrected scattering and absorption coefficients of optically abnormal targets from time-of-flight (TOF) data obtained in time-resolved transillumination experiments is successfully analyzed. Several independent sets of experimental TOF data are used to show that the random walk methodology is able to quantify the size and optical properties of embedded targets with an error ≤25%. The underlying theoretical assumptions of the model are tested. Finally, the effect of lateral boundaries on time-resolved measurements of light transmitted through slabs of finite thickness is considered within the framework of a random walk model.
Nonlinear Multigrid Optimization for Soft Tissue Imaging Using a Bayesian Optical Diffusion Approach
Authors: Webb Kevin J. , Ye Jong C. , Bouman Charles A. , Millane Rick P.
Published: February 2023

Optical diffusion tomography involves the reconstruction of an object cross section from measurements of scattered and attenuated light. While Bayesian approaches are well suited to this difficult nonlinear inverse problem, the resulting optimization problem is very computationally expensive. We propose a nonlinear multigrid technique for computing the maximum a posteriori (MAP) reconstruction in the optical diffusion tomography problem. The multigrid approach improves reconstruction quality, by avoiding local minima, and it dramatically reduces computation. Each iteration of the algorithm alternates a Born approximation step with a single cycle of a nonlinear multigrid algorithm. Reconstructed images are shown for examples using a tissue model.
Cerebral Hemodynamics Measured by Near-Infrared Spectroscopy at Rest and During Motor Activation
Authors: Franceschini Maria Angela , Fantini Sergio , Toronov Vlad , Filiaci Mattia E. , Gratton Enrico
Published: February 2023

Near-infrared spectroscopy and imaging are powerful tools to detect and continuously monitor the cerebral hemodynamic and oxygenation changes induced by brain activity. However, in addition to the focal neuronal-activation-induced hemodynamic signals, near-infrared methods are also sensitive to the cerebral hemodynamic fluctuations of systemic origin associated, for instance, with the arterial pulse, respiration, and heart rate fluctuations. We have used near-infrared spectroscopy to non-invasively measure the cerebral hemodynamics in a human subject at rest. We have observed hemoglobin oscillations at the heart rate (~1 Hz), respiratory rate (~0.2 Hz), and at lower frequencies that are associated with heart rate fluctuations and vasomotion activity. With near-infrared imaging, we have measured the spatial maps of temporal changes in the cerebral oxy- and deoxy- hemoglobin concentrations during motor activity (hand tapping). We have found a more localized activation-induced response in the deoxy-hemoglobin map with respect to the oxy-hemoglobin map. This result can be explained by the observed synchronization between the sequence of tapping/rest periods and several systemic physiological oscillation such as the arterial pulse, respiration, and heart rate fluctuations.
Functional optical imaging of human brain activity—A study with a time-resolved optical tomographic system—
Authors: Tamura Mamoru , Hoshi Yoko
Published: February 2023

Using a newly developed 64-channel time resolved optical imaging system, we have attempted to obtain quantitative functional images of brain activity. For the human head, the reflectance tomographic imaging of the changes in oxy-hemoglobin, deoxy-hemoglobin and total hemoglobin associated with neural activation were obtained where the changes were given as absolute concentration changes. The obtained optical functional images were superimposed on 3-D images of the subject’s brain reconstructed from MRI. The activation area was found to be very reasonable. The optical imaging system employed here can be applied to subjects of all ages and used at the bedside, and thus presents new possibilities for neuropsychological studies.
Fluorescence Lifetime Imaging System for Biomedicine and Spectroscopy
Authors: Cole M. J. , Dowling K. , French P. M. W. , Jones R. , Parsons-Karavassilis D. , Siegel J. , Lever M. J. , Neil M. A. A. , Juškaitis R. , Wilson T. , Dymoke-Bradshaw A. K. L. , Hares J. D.
Published: February 2023

Fluorescence lifetime measurements permit both detection of specific fluorophores and quantitative monitoring of their local environment for biomedical imaging and other applications. Fluorescence lifetime imaging (FLIM) can provide non- invasive functional/diagnostic imaging by exploiting the sensitivity of fluorescence lifetime to the local environment. This paper reviews our development of a 2-D FLIM time domain instrument based on ultrafast solid-state laser technology that is potentially portable and inexpensive. We have applied this 2-D FLIM system to animal tissue in vitro using autofluorescence to obtain strong contrast between different types and states of tissue. We also report first results of a whole field 3-D FLIM microscope.
Compact NIR Confocal Imaging Raman Microspectrometer
Authors: Dickensheets David L. , Crowder D. Michelle , Faulhaber Matthew J. , Schoen Christian L. , Carron Keith T.
Published: February 2023

Advances in the fields of micro-optics and micro-mechanics are enabling the construction of increasingly miniature optical instruments capable of high-resolution imaging and spectroscopy. Such instruments will be of considerable practical value for a range of in vivo imaging and spectroscopy techniques, where use of traditionally sized optical instrumentation is a barrier preventing access to many sites in the body. In this paper we describe a compact confocal laser scanning microscope and Raman microspectrometer that incorporates a micromechanical scanning mirror in a compact optical design. We present preliminary images and spectra obtained with a prototype instrument (λ=852 nm, N.A.=0.2, 1 μm spot size), and discuss a development path that would employ micro-optical and micromechanical elements in an endoscopically deployed confocal imaging microspectrometer.
An Animal Model for In-Vivo Characterization of Laser Induced Retinal cellular Pathology and Recovery Processes
Authors: Zwick H. , Stuck B. E. , Elliott W.R. , Lund D.J. , Schuschereba S.T. , Li G.
Published: February 2023

In the high numerical aperture eye of the snake, the photoreceptor matrix can be imaged in vivo under anesthetized conditions, providing a unique capability to image acute photic damage effects on photoreceptor and anterior retinal blood cell dynamics in response to retinal laser injury. New insights into photic damage and neural repair mechanisms become available from such in vivo cellular observations.
Combined optical coherence and two-photon excitation microscopy
Authors: Beaurepaire E. , Moreaux L. , Mertz J.
Published: February 2023

We demonstrate simultaneous imaging by optical coherence microscopy (OCM) and two-photon-excited fluorescence (TPEF) microscopy. Independent contrast mechanisms derived from fluorescence and backscattered light provide complementary information on biological tissues. The coupling of OCM and TPEF microscopy is natural in that the two imaging modes may be run off the same laser source. The confocal arrangement for OCM provides a sub-micrometer resolution compatible with TPEF microscopy.
Two-Photon Microscopy based Tissue Biopsy
Authors: So Peter T. C.
Published: February 2023

Two-photon microscopy is a powerful technique that allows three- dimensional imaging of tissue structures with sub-micron resolution. Equally important, two-photon microscopy uses excitation light in the near infrared spectral range, where tissue absorption and scattering is minimal. Two-photon excitation allows non-invasive tissue imaging down to a depth of a few hundreds of micrometers for typical tissues. The use of two-photon excitation for non-invasive biopsy has been suggested but remain unrealized. The progress of two-photon microscopy for clinical tissue biopsy will depend on a number of key technological advances such as the video rate imaging of 3-D tissue structures and the availability of spectral resolution to determine tissue metabolic states and biochemical components.
Strongly suppressed diffuse scattering in periodic graphene metamaterials
Authors: Zhang Tieyan , Yu Jiachen , Xing Li , Wulan Qiqige , Liu Zhijun
Published: February 2023

As an emerging two-dimensional material, graphene offers an alternative material platform for exploring new metamaterial phenomena and device functionalities. In this work, we examine diffuse scattering properties in graphene metamaterials. We take periodic graphene nanoribbons as a representative example and show that diffuse reflection in graphene metamaterials as dominated by diffraction orders is restricted to wavelengths less than that of first-order Rayleigh anomaly, and is enhanced by plasmonic resonances in graphene nanoribbons, as similar to metamaterials made of noble metals. However, the overall magnitude of diffuse reflection in graphene metamaterial is less than 10−2 due to the large period to nanoribbon size ratio and ultra-thin thickness of the graphene sheet, which suppress the grating effect from the structural periodicity. Our numerical results indicate that, in contrast to the cases of metallic metamaterials, diffuse scattering plays a negligible role in spectral characterization of graphene metamaterials in cases with large resonance wavelength to graphene feature size ratio, which corresponds to typical chemical vapor deposition (CVD)-grown graphene with relatively small Fermi energy. These results shed light on fundamental properties of graphene nanostructures and are helpful in designing graphene metamaterials for applications in infrared sensing, camouflaging, and photodetection, etc.
Heterogeneously integrated III–V-on-Si laser with embedded photonic molecule mirrors
Authors: de Rezende Guilherme F. M. , Frateschi Newton C. , Roelkens Gunther
Published: February 2023

We have designed, fabricated, and characterized a III–V-on-Si laser employing photonic molecule mirrors with high potential for laser tunability and control. Resonant mirrors are realized by tailoring supermodes of coupled microrings. A laser threshold of 40 mA (L-band), series resistance of 10 Ω, and side mode suppression ratio of 40 dB are demonstrated.
Fiber Optic Microprobe
Authors: Davis Lloyd M. , Alvager Torsten
Published: February 2023

A fiber optic microprobe using pulsed ultraviolet laser excitation allows in vivo detection of fluorescence emission spectra, time resolved from the large scattering signal.
In-Situ Measurements of Surface Ordering on Single Crystal Electrode Surfaces by Optical Second Harmonic Generation
Authors: Shannon V. L. , Koos D. A. , Richmond G. L.
Published: February 2023

The characterization of the single crystal electrode surface is of central importance to a detailed understanding of interfacial chemistry. In this paper, we report the first in-situ measurements of electrode surface structure by an optical technique. Sensitivity to surface ordering and symmetry is observed for silver single crystals.
Vibrational Mode Coupling in Multiresonant Molecular Cars
Authors: Carlson Roger J. , Wright John C.
Published: February 2023

A simple rule is presented which describes the selective enhancement of a single vibrational mode of an electronically excited state in CARS.
Analytical Applications of High Resolution Infrared Tunable Diode Laser Spectroscopy
Authors: Fried Alan , Sams Robert
Published: February 2023

Measurement techniques based upon absorption of mid-infrared radiation (2.5 - 25 μm) have proven to be extremely attractive in numerous research, environmental and industrial applications. Studies of atmospheric trace gases in both the laboratory and the ambient environment (1-3); as well as studies of flame (4), combustion (5), and laser diagnostics (6); studies of emissions from cigarette smoke (7), automobiles (8) and power plants (9); analysis of industrial process stream compounds (10); and moisture determinations in integrated circuit packages (11) are but a few examples of the broad range of such applications. This diversity is a direct result of the fact that many constituents exhibit moderate to strong absorption features in the mid- infrared, sometimes referred to as the "fingerprint region". Obviously, to cover all such applications is well beyond the scope of this paper, and we will therefore restrict our discussion of analytical applications of high resolution IR spectroscopy to one of the fasted growing and widespread areas: laboratory and ambient environmental studies of important atmospheric trace gases. In particular, we will focus our discussion on studies utilizing tunable diode lasers (TDLs) as the infrared radiation source, although one example of measurements utilizing another IR source will also be given. Even this specific topic is too extensive to comprehensively cover in such a short review, and we thus only attempt to give a broad overview of some of the more recent analytical applications of TDLs in studying atmospheric gases. Purely spectroscopic applications, which are equally numerous and very important, are not covered here.
Trace Copper Detection in High Salt Matrices by Laser Enhanced Ionization Spectrometry
Authors: Havrilla George J. , Carter Christopher C.
Published: February 2023

The detection of trace levels of copper in high salt matrices, including matrices with low ionization potential elements such as alkali and alkaline earth elements and metal sulfate solutions, present unique challenges to conventional methods of analysis like inductively coupled plasma (ICP) atomic emission spectrometry and atomic absorption (AA) spectrometry. In each case the conventional method of analysis possesses sufficient sensitivity to perform the analysis at the 1 ng/mL level in aqueous solutions (1). However in matrices such as seawater and metal sulfate solutions chemical and spectroscopic interferences prevent these methods from achieving this level of sensitivity. This paper describes the use of laser enhanced ionization (LEI) spectrometry to detect copper in 0.5 M sulfate solutions and synthetic seawater at the 0.5 ng/mL level.
Study of Copper Underpotential Deposition on Gold using Optical Second Harmonic Generation and the Quartz Crystal Microbalance
Authors: Bennahmias Mark J. , Lakkaraju H. Sarma , Stone Bradley M. , Ashley Kevin , Lazaga M.
Published: February 2023

The second harmonic (SH) signal was generated using 1.064 μm radiation from a Nd:YAG laser operating at a 5 Hz repetition rate. The beam diameter was 3 mm at the electrode surface with an operating energy per pulse of about 8 mJ. The collected SH light was focused onto the entrance slit of an f/3 monochromator that was tuned to 532 nanometers. A photomultiplier was used for detection of the SH signal and the output averaged by a gated integrator/boxcar averager. A filter removed the 1.064 micron fundamental from the collected SH radiation. A reference SH signal was generated using a similar detection line from a quartz crystal, tuned to the peak of a Maker fringe, in order to normalize out fluctuations in the laser output. A modified, three electrode, spectroelectrochemical cell with a VIS/NIR transparent window was used. The reference electrode used was a Ag/AgCl microreference tip, and was placed approximately 1 mm from the edge of the gold mirror electrode. A platinum auxiliary electrode provided a current source for the cell.
Fluorescence Analysis of Microdroplets: An Approach to Single Molecule Detection
Authors: Ramsey J. M. , Whitten W. B.
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 place (1). 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 molar. 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.
Do You Really Know What You Are Looking At - "True" or "False" Signals in Laser-Enhanced Ionization Spectrometry
Authors: Axner Ove , Sjöström Sten
Published: February 2023

"Things are not always what they seem to be"
- is a phrase which particularly concerns spectroscopists. This is nicely illustrated by the present paper which discusses and exemplifies a situation which, for more than a decade, has passed virtually unnoticed within the community of spectroscopists which are working with ionization techniques in flames, especially the Laser-Enhanced Ionization technique, (LEI), namely the influence of scattered laser light.
Measurements of High Temperature Superconductors by Thermal Modulation of Electrical Conductivity.
Authors: McLaren Robert , Dovichi Norman J.
Published: February 2023

The discovery of materials that show superconductivity at a temperature above the boiling point of nitrogen1 has generated a flood of interest in the area of high temperature superconductivity. The large change in resistance of a superconducting sample at its transition temperature makes it appropriate for analysis by thermal modulation techniques. Studies are presently being performed on the YBa2Cu3O7 and Bi-Sr-Ca-Cu-O classes of high temperature superconductors.
Robust Fitting of CARS Spectra for Temperature Measurement in Hostile Combustion Environments
Authors: Dunn-Rankin D.
Published: February 2023

As Coherent Anti-Stokes Raman Scattering (CARS) becomes actively applied in complex, hostile, and practical combustion systems, the trade-off between reliability and accuracy of CARS temperature measurement becomes important. Noise in the CARS signal can undermine detailed spectral fitting techniques, leaving calculated temperatures somewhat uncertain. This paper uses the CARS fitting code developed at Sandia National Laboratories (Palmer, 1989) to explore the robustness of “quick” fit, or integral fitting methods, as a technique for avoiding the difficulties in fine detail fitting of noisy CARS data. The theoretical temperature resolution from such integral fitting is much lower than for detailed calculations, but the reliability of the temperature can be significantly improved.
Two-Photon-Excited Stimulated Emission from Atomic Hydrogen in Flames
Authors: Goldsmith J. E. M.
Published: February 2023

Two-photon-excited stimulated emission (SE) has been studied in a variety of atomic and molecular systems for over a decade. However, the effect that SE may have on diagnostic applications of multiphoton-excited fluorescence (FL) detection, and the potential use of SE detection as a useful technique in its own right, have received little attention until a recent report describing SE from atomic oxygen in flames.1 In this summary, we describe two-photon-excited SE and FL measurements of atomic hydrogen in flames.
How to find the limit of sensitivity for DNA-base identification by laser-induced fluorescence
Authors: Köllner Malte , Wolfram Jürgen
Published: February 2023

To optimize laser-induced fluorescence experiments, we will undertake to find the limit of sensitivity - in numbers of molecules - for experiments that identify certain types of molecules, e.g. DNA-bases labelled with dyes. The experimental method to be considered is single photon counting or time-con-elated-single-photon-counting (TCSPC). The basic idea for the analysis is to look at the experiment from the data-analysis side, to find (a) an optimum statistical procedure for the analysis problem and (b) to find out what signal strength it needs.
The Influence of External Stress on the Molecular Order of Monolayer Assemblies
Authors: Evans Christine E. , Bohn Paul W.
Published: February 2023

Monolayer assemblies of molecules offer chemists an intriguing system for study. In addition to the variety of possible applications ranging from chemical sensing to corrosion inhibition, the structured simplicity of these two-dimensional arrays makes possible more accurate predictions of molecular behavior. Thus, these well-ordered systems present a unique opportunity to correlate theoretical predictions of molecular- scale structure to experimental measurements. These correlations are of particular importance in understanding the response of molecular arrays to external perturbations. Although a number of physical and chemical sources of external stress are possible, initial studies presented here will focus on the influence of temperature on the molecular-scale order.
Degenerate Four Wave Mixing techniques for Combustion Diagnostics
Authors: Ewart P
Published: February 2023

Degenerate Four Wave Mixing, DFWM, is a third order nonlinear optical process which has been used for high resolution spectroscopy and, by virtue of its phase conjugating property, for adaptive optics(1). The process is closely related to Coherent Anti-Stokes Raman Scattering, CARS, which is widely used for temperature and concentration measurements of majority species in combustion studies(2). Minority species, on the other hand are usually detected using the more sensitive technique of Laser Induced Fluorescence, LIF. DFWM shares the coherence property of CARS and the sensitivity of LIF and thus provides a coherent technique for the detection of minority species such as radicals and combustion intermediates. This new technique has the added advantageous property of phase conjugation. DFWM signals have been generated from atomic Na in seeded flames(3,4) and the potential of the technique for combustion diagnostics was demonstrated by the detection of the OH radical in a methane/air flame(3). More recent developments have included two-dimensional single-shot imaging of atomic and molecular distributions(5,6), accurate flame temperature measurements based on rotationally resolved DWFM spectra(7), broadband or multiplex DFWM in flames(8) and two-dimensional mapping of temperature fields(9).
First, detection of the visible absorption spectrum of H2O+ and D2O+
Authors: Das Biman , Xia Zuyong , Marawar Ravi , Farley John W.
Published: February 2023

The visible emission spectrum of the water cation, H2O+, is a prominent feature in comet tails, and is often observed in laboratory discharges. However, until now the visible electronic spectrum has never been observed in absorption. We have used a tunable ring dye laser and a velocity-modulated discharge to detect the

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visible electronic spectrum in absorption, in H2O+ and D2O+.
Diagnostics for Emission Monitoring for Hazardous Waste Incineration
Authors: Cool Terrill A.
Published: February 2023

The unique attributes of resonance-enhanced multiphoton ionization/time-of-flight mass spectrometry (REMPI/TOFMS) for rapid, ultrasensitive, and selective detection of toxic organics make it a promising new tool for quantitative evaluation of incinerator performance. The spectral selectivity of resonance ionization mass spectrometry, realizable with jet-cooling, eliminates the need for the time-consuming capillary column sample separation of conventional GC/MS analysis. Recent research indicates that real-time repetitive monitoring of a wide class of trace emissions at the part-per-billion level (ppb) is possible with the REMPI/TOFMS method.[1,2] Indeed, REMPI detection capabilities for specific compounds are expected to significantly influence stategies for the use of surrogates for stack gas monitoring.
Degenerate Four-Wave Mixing in a Methane/Air Flame Using a Regeneratively Mode-Locked Ti:Sapphire Laser
Authors: Linne M.A. , Fiechtner G. J.
Published: February 2023

The potential of resonant Degenerate Four-Wave Mixing (DFWM) for measurements of major and minor species concentrations and temperature in reacting flows has been established by several groups1. Spatial resolution has been demonstrated, as has two-dimensional planar imaging. Perhaps most significantly, large signals have been observed at moderately high pressures (1100 Torr)2, establishing the potential for measurements inside practical combustion systems. As a result, a good deal of research is currently devoted to understanding the fundamental physical aspects of the technique.
On-Line Analysis of Single Microparticles by Rapid Single-Particle Mass Spectrometry
Authors: Johnston M. V. , Carson P.G. , Neubauer K.R. , Mansoori B.A. , Wexler A.S.
Published: February 2023

Numerous methods have been developed to analyze particulate matter in ambient aerosols. Typically, particle composition is measured by removing the particles from the gas by filtration or impaction and transporting the sample to a laboratory where “off-line” analysis is performed with either bulk or single particle analytical techniques. There are a several difficulties with these methods. First, the sample is collected over an extended period of time, so short term temporal variations in the composition cannot be resolved. Second, compounds may condense on or evaporate from the impactor surface or filter over the course of sampling, altering their composition. Third, the turnaround time between sampling and analysis is slow. For these reasons, off-line analysis based upon filtration or impaction cannot be easily adapted to real-time sampling and analysis and they may not give analytical results that are representative of the true composition. These problems can be overcome with on-line methods of analysis.
New Horizons for Solid-State Lasers
Authors: Bischel William K.
Published: February 2023

There has been an explosion of new products introduced during the past year in the area of pulsed solid state lasers and their tunable accessories. In this talk I will discuss two emerging new technologies that may have a significant impact on laser development for applications in chemical analysis: high repetition rate YAG lasers and new “quasi-phase matched” periodically poled nonlinear materials.
A Study of Aerosol-Cloud Interaction using Laser Microprobe Mass Analysis
Authors: Gieray R. , Wieser P.H.
Published: February 2023

Cloud formation, radiative properties and cloud droplet chemistry is strongly affected by the size distribution and chemical composition of the atmospheric aerosol on which the cloud has been formed. Once a particle is incorporated into a droplet, chemical reactions in aqueous solution may occur changing the loading of air pollutants (e.g. oxidation of dissolved SO2 under the catalytic influence of metal ions). In addition the incorporation of airborne particles into cloud droplets play an important role in determining the atmospheric residence time of air pollutants.
Raman Spectroscopy of Phosphonate Solutions by Real time, In-Situ Fiber Probe With Metal Oxide Adsorbent
Authors: Dagenais D.M. , Ewing K.J. , Bucholtz F. , Aggrawal I.D.
Published: February 2023

Fiber optic Raman spectroscopy is a powerful tool for in-situ detection and selectivity, but it lacks sensitivity. Significant enhancement has been obtained by pre-concentration in a matrix of metal oxide, leading to selective in-situ detection of traces of DMMP, DIMP and MPA both in water and in gas phase, for a potentially portable device for detection of traces of chemical breakdown products.
Quantitative Detection of CH Radicals by Laser-Induced Fluorescence in ARCJETS and Flames
Authors: Luque Jorge , Juchmann Wolfgang , Jeffries Jay B. , Crosley David R.
Published: February 2023

Flames and chemical vapour deposition (CVD) processes are examples of systems where the chemistry involved is very complex, and the outcome of final products is often strongly dependent on intermediate species present in very low concentrations. Optical methods are ideal for detection of these short-lived transient molecules, and laser-induced fluorescence offers the advantage of simultaneous measurements of concentrations and temperatures1.
Mean Orientation Measurements of Fibrous Aerosols in Atmospheric Boundary Layer Turbulence
Authors: Newsom R. K. , Bruce C. W. , Jelinek A. J. , Thurston M.
Published: February 2023

It is well known that thin axisymmetric particles such as fibers sedimenting in a quiescent medium with a Reynolds number of order unity (R
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≈ 1) will align their symmetry axes perpendicular to their fall direction. It is not clear to what extent this behavior remains in effect when the particle is subject to the randomizing forces imposed by turbulence. The goal of this research is to establish a firm connection between the degree of horizontal orientation of a large ensemble of fibers in the atmospheric boundary layer and the mean kinetic energy density associated with the turbulent motion of the air.
Spatial maps of analyte and Ar buffer gas atoms and ions by LIF in ICP-MS
Authors: Duersch B. , Chen Y.B. , Ciocan A.C. , Farnsworth P.B.
Published: February 2023

Laser induced fluorescence as a selective and sensitive diagnostic tool is used for ion beam analysis downstream from the skimmer in an ICPMS. Using selected spectral lines, analyte atoms and ions and Ar metastable atoms are measured for a range of ICP operating conditions, vacuum pressures and over a wide range of element’s masses. To our knowledge, optical measurements of ions extracted from an ICP, either by emission [1-2] or by laser induced fluorescence [3-4], were limited to the first stage of ion extraction and only few probe elements were chosen.
Effects of Valence Electron Shell Structure on Ion Beam Sputtered Neutrals
Authors: He Chun , Postawa Z. , Rosencrance S. , Chatterjee R. , Reiderer D. E. , Garrison B. J. , Winograd N.
Published: February 2023

Energetic ion impact on a solid initiates a complex dynamical chain of events which include atomic motion, electronic excitation, ionization, and desorption of atomic and molecular species. Measurements on the desorbed particles during the ion-solid interaction process provide a valuable opportunity to understand the ion-solid interactions.[1-2] For more than three decade, research has been focused on understanding the formation of electronic excited states subsequent to ion bombardment in order to establish the role of inelastic energy transfer on ionization and sputtering yield[2]. The widely accepted conclusion is that the rate of relaxation is determined by the energy gap between the excited and ground state, i.e., the larger the magnitude of the excitation energy the more rapid relaxation of the electronic excitation.