bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Gamut of Colors Seen In Airplane Windows
Authors: Bohren Craig F.
Published: February 2023

The colored patterns seen when airplane windows are viewed through polarizing filters have been commented upon many times (see e.g., [1,2]). Yet the gamut of colors seems not to have received quantitative treatment. Are all colors equally likely and of equal purity? I address these questions in this paper, a technical version of a popular article [3].
Reflections from Large Rippled Surfaces of Water
Authors: Bean Charles P.
Published: February 2023

Under the title of this paper, Minnaert1 discusses the work of Hulburt2 on the reflection of the sun by ocean waves. If the sun is low enough, one sees a bright patch of reflected light that is more or less triangular in shape with the base at the horizon. The position of the tip of the patch depends on the height of the observer above the water while its angular width at the horizon is quite invariant. Hulburt calculated this width at the horizon on the assumption that the waves were randomly oriented reflecting surfaces of a given maximum slope. He numerically calculated this width as a function of the maximum slope of the wave and the altitude of the sun. Hulburt stated2 that this relationship "is easily written down from spherical trigonometry but is too long to give here; it is made of six equations with parameters which may not readily be eliminated."
Finnish Halo Observing Network: Search for Rare Halo Phenomena
Authors: Pekkola Marko
Published: February 2023

During the first half of this century research on halo phenomena seems to have been in a chaotic state. Particularly the lists and theoretical views of Bravais (1847), Pernter and Exner (1922), Minnaert (1954) and Visser (1957, 1960) about the rarest known halos did not have much in common.
The Opening Rate of the Transverse Cusp Diffraction Catastrophe from Oblate Spheroidal Water Drops
Authors: Dean Cleon E. , Marston Philip L.
Published: February 2023

The opening rate of the transverse cusp versus oblateness for water drops was calculated. The work suggests the form of a naturally occurring generalized rainbow.
Seeing Polarisation with False Colour
Authors: Jackson Seán
Published: February 2023

There are many examples of polarised light in nature, such as sky and clouds, the solar corona, reflections from glossy surfaces, minerals, and even the Crab Nebula.
Horizon Brightness Revisited: Measurements and a Model
Authors: Lee Raymond L.
Published: February 2023

To the uninitiated, the clear daytime sky seems such a commonplace that its radiance and brightness distribution surely must be well known. Researchers in fields ranging from solar energy engineering1,2 to atmospheric optics3,4 have repeatedly measured and modeled the angular distribution of clear-sky radiances, and they have published scores of papers on the subject. What can be left to know?
Simulation of Pollen Caused Coronas
Authors: Tränkle E. , Mielke B.
Published: February 2023

Coronas with elliptical and rhompic shapes were observed and photographed by the Finnish halo observer group [1].
Light Scattering by Capped-Column Ice Crystals
Authors: Takano Y. , Liou K. N.
Published: February 2023

Capped columns have been frequently observed in cirrus and mixed-phase clouds.
The Effects of Ice Crystal Structure on Halo Formation: Cirrus Cloud Experimental and Ray Tracing Modeling Studies
Authors: Sassen Kenneth , Knight Nancy , Takano Y. , Heymsfield Andrew J.
Published: February 2023

During the 1986 Project FIRE Intensive Field Observations (IFO) program, four deep, large-scale cirrus cloud systems were jointly studied by a ground-based polarization lidar at Wausau, WI and the NCAR King Air aircraft.
Catastrophe optics: light caustics in nature
Authors: Nye J. F.
Published: February 2023

When sunlight is reflected from rippling water the emerging wavefronts are correspondingly uneven.
Simulating Rainbows and Halos in Color
Authors: Gedzelman Stanley David
Published: February 2023

Monte Carlo simulations of halos have helped confirm the precise mechanism leading to a number of the unusual arcs.
Rainbow Scattering by a Coated Sphere
Authors: Lock James A. , Jamison J. Michael , Lin Chih-Yang
Published: February 2023

On the basis of ray theory, the trajectory of the first order rainbow ray through a coated sphere is expected to be as shown in Fig. 1
Using Natural Optical Phenomena to Introduce Audiences to the Information Superhighway
Authors: Draper Clifton W.
Published: February 2023

Rainbows, mirages and other optical phenomena in the lower atmosphere are beautiful gifts of nature. Through the use of simple ray and a healthy dose of hand waving, they are also relatively simple to explain in terms of optical physics. In part, the information superhighway is made possible by the replacement of copper wires with thin strands of glass known as optical fiber. What happens to light inside the optical fiber has much in common with the natural phenomenon we know as the mirage. The use of colorful images and anecdotal stories can do much to enhance what otherwise might be a boring technical discussion, or even worse, a disastrous non-technical talk before a lay audience. Most audiences could care less about the theoretical Rayleigh scattering limit in dB/km for ultrapure silica glass. These same audiences will remember that at the mid-latitudes it takes more than sunshine and rain to find a rainbow in the sky around lunch time.
Generalized tertiary rainbow of slightly oblate drops: observations with laser illumination
Authors: Langley Dean S. , Marston Philip L.
Published: February 2023

Oblateness in drops has been shown to produce caustics in the farfield scattering that are more complicated than the ordinary rainbow [1-7]. The complicated caustics generated are examples of "diffraction catastrophes" involving the coalescence of more than the two rays present for the usual Airy caustic [8,9]. Such diffraction catastrophes produced by scattering from oblate drops of water have been referred to as "generalized rainbows" [2,7]. While the analysis of such caustics is relevant to understanding complexity in wave propagation [8-11]. consideration of the scattering by oblate drops is helpful for anticipating whether or not generalized rainbows are likely to be visible in sunlit raindrops. The situation usually considered is the one which has the greatest symmetry: horizontal illumination of an oblate drop having a vertical symmetry axis. Generalized rainbows occur because of vertical focusing within the drop which causes the vertical curvature of the outgoing wavefront to vanish in the equatorial plane. Let D be the diameter of such a drop in the equatorial plane and let H the height. A relevant question is whether the values of the aspect ratio q = D/H required to produce the vertical focusing are sufficiently close to unity so as to be present for naturally falling raindrops. Naturally falling drops are ordinarily only slightly oblate because of the flow of air past the drop [12]. Previous laboratory observations and calculations indicate that for rays having two or three internal chords (corresponding to primary and secondary rainbow mechanisms), the required values of q are so large as to make their natural occurrence extremely rare, if ever [3-7]. It was calculated and observed that for drops having 6 chords, a bright complicated caustic was produced for q near 1.08. It was also predicted that cusps would be present for even smaller q as part of the unfolding of an axial glory caustic (as has been observed for bubbles in water [11]).
Identification and Frequency of 23° Parroids
Authors: Riikonen Marko , Ruoskanen Jukka , Pekkola Marko , Moilanen Jarmo
Published: February 2023

A marginally known pyramidal halo that can be e.g. referred as “23° parroid” is unexpectedly emerging at least as one of the three most frequent rare halos. It appears that during this century hundreds of high solar elevation 23° parroids have been missidentified as 22° upper tangent arcs. An Antarctic display from year 1950 offers an example where a low solar elevation 23° parroid has been missinterpreted as a Parry arc. In Finland during the April-August period numerous 23° parroids have been sighted annually in weak or mediocre halo displays since 1994 when the error in the identification criteria was first confirmed. Due to unknown reason the visibility of 23° parroids seems to peak in sultry days.
Atmospheric Refraction and its Effects on Sunrise and Sunset
Authors: Sampson Russell Dean
Published: February 2023

Observed timings of 244 sunrises and 125 sunsets over the span of three years were used to determine the atmospheric refraction of the Sun's upper limb at the moment of sunrise and sunset on a zero horizon. Sunrise and sunset was defined as the moment the upper limb of the Sun appeared above the local horizon. All observations were done from two sites in Edmonton, Alberta separated by a distance of 2.2 kilometers.
Optical Doppler Tomography: Imaging In Vivo Skin Blood Flow
Authors: Chen Z. , Milner T.E. , Srinivas S. , Nelson J.S.
Published: February 2023

Summary not available.
“Recycling” Wasted Photons: A Device to Increase Laser Energy Used in Surgery
Authors: Ross E.V. , Raythen J.S. , Farinelli W.A. , Naseef G.S. , Anderson R.R. , Gaudette T. , DiMarzio C.A.
Published: February 2023

The reflectance of human skin is wavelength-dependent and ranges from 15% to 70% through the visible and near-infrared regions of the electromagnetic spectrum. These reflected photons are scattered into the environment and essentially “wasted” in surgical laser applications.
Anatomy, Colour and Treatment of Port Wine Stains
Authors: van Gemert Martin JC , Verkruysse Wim , Smithies Derek J , Milner Thomas E , Nelson J Stuart
Published: February 2023

Clinical response of port wine stains (PWS) to laser therapy, using currently accepted parameters (585 nm wavelength, 0.45 ms pulse duration, 5-10 mm spot diameter, single pulses), cannot be accurately predicted. Extensive histologic analysis [1], three dimensional reconstruction [2] or classification [3,4] of vascular anatomy, and modeling [5,6] have not provided conclusive insight as to why some PWS respond poorly to laser treatment.
A Critical Analysis of Thermal Injury and Laser Resurfacing
Authors: Venugopalan Vasan
Published: February 2023

The results of skin resurfacing studies are analyzed using models for laser coagulation and ablation with the hope of identifying the laser parameters most critical in alfecting a positive clinical outcome.
Advances in Laser Skin Resurfacing
Authors: Fitzpatrick Richard
Published: February 2023

CO2 laser resurfacing of facial wrinkles, acne scarring, and other cutaneous lesions has generated tremendous interest and excellent clinical results. The recent introduction of the erbium laser has added further sophistication. Principles of their laser/tissue interaction and clinical use are presented.
Laser-Assisted Hair Removal
Authors: Grossman Melanie C.
Published: February 2023

This paper examines the various laser-assisted hair removal systems available and discusses practical clinical issues of patient selection, efficacy and technique for each system.
Hair depilation using the Ruby laser in a continuous mode - correlation between efficacy of treatment and melanin content of hair and the growth phases of hair at a specific site
Authors: Liew SH , Linge C , Grobbelaar AO , Gault D , Green C
Published: February 2023

There is a clinical need for an efficient and reliable method of hair removal from the body. The Ruby laser in a continuous mode has been used to achieve selective photothermolysis of hair follicles with encouraging results (1, 2). However, the efficacy of this treatment appears to vary from patient to patient with dark coloured hair. Based on the theory of selective photothermolysis, it is logical to assume that the darker one’s hair is, the more effective the laser treatment would be. It is also not known if laser depilation is more effective if hair is treated while it is in its anagen phase. A prospective clinical study was carried out to answer these questions.
Influence of Hair Growth Cycle on Hair Follicle Destruction by Pulsed Ruby Laser Treatment in Newborn Mice
Authors: Lin Tai-Yuan David , Manuskiatti Woraphong , Dierickx Christine , Farinelli William A. , Fisher Marney , Flotte Thomas , Baden Howard , Anderson R. Rox
Published: February 2023

It has been shown that using normal mode ruby laser pulses (694 nm) is an effective method of selectively destroying brown or black pigmented hair follicles in adult Caucasians (Grossman et al, 1996). The pigment, melanin, contained within the dark hair follicles acts as a target for light absorption when exposed to a well characterized range of wavelengths (Anderson and Parrish, 1981). Based on principles of selective photothermolysis, exposure to carefully chosen wavelength and pulse duration characteristics result in preferential absorption by the target pigment and sufficient heating to cause localized cellular destruction (Anderson and Parrish, 1983).
Ultraviolet Laser Etching: Diatomic Temperatures by Laser-Induced Fluorescence Measurements
Authors: Dreyfus R. W. , Walkup R. E. , Kelly Roger , Srinivasan R.
Published: February 2023

Laser-induced etching is receiving significant attention, motivated by applications in microelectronics and medicine and by long standing concern about optical damage phenomena. In the present experiments, we emphasize etching with pulsed UV (excimer) lasers in the low fluence, i.e. near threshold, region. Under these conditions etching has been attributed to a variety of phenomena, among them thermally activated vaporization and photochemical bond breaking processes. The present work is aimed at distinguishing between the thermal and electronic processes for several materials. According to the thermal model, one requires a sufficiently high peak temperature that vaporization is the primary source of surface etching.
Developments in Raman Spectroscopy for Ion Implant Monitoring
Authors: de Wilton A.C. , Simard-Normandin M. , Wong P.T.T.
Published: February 2023

As part of a strategy for development of in situ process monitoring for VLSI technology we are evaluating a number of optical techniques applicable to implantation and annealing processes. Techniques with potential for non-destructive characterization of patterned production wafers, rather than test wafers, are of primary interest. Consequently, the techniques to be considered must (i) be non-contact and non-contaminating; (ii) have high spatial resolution; (iii) provide rapid real time analysis; and (iv) use equipment that is adaptable for automatic or turn-key operation. Raman spectroscopy meets these criteria and the technique is well suited for studying materials for silicon technology (1). Features in the Raman phonon spectrum of implanted silicon can provide information on ion-damage prior to annealing or on the activation and distribution of dopant after annealing (2). In this paper we investigate the limits to the dose and energy of boron implants which can be detected by Raman spectroscopy.
Surface CARS Spectroscopy with Optical Waveguides
Authors: Hetherington W.M. , Ho Z.Z. , Wijekoon W.M.K.P. , Koenig E.W.
Published: February 2023

Using the planar optical waveguide geometry, coherent anti-Stokes Raman scattering becomes a very sensitive type of vibrational spectroscopy for the study of surface structure and chemistry. The waveguide structure consists of a film (about one micron thick) of a material such as ZnO on a fused silica substrate. Laser fields can be constrained by total internal reflection such that they propagate through the film as guided waves. The concept is to perform CARS using the evanescent fields extending above the waveguide surface. The key to making this a very attractive form of surface spectroscopy is the establishment of an interference condition within the film, thereby eliminating the contribution from the vibrationally resonant or nonresonant third order susceptibility of the film itself. The remaining signal consists mainly of the signal from the surface and any surface adsorbates. With this technique, the Raman spectrum of interfacial species can be observed over the 0 to 4000 cm-1 range under environments ranging from UHV to condensed phases.
Quantum-Resolved Gas-Surface Scattering: NH3 from Au (111)
Authors: Kay Bruce D. , Raymond T. D. , Coltrin Michael E.
Published: February 2023

We have measured angular, velocity, and quantum-state distributions for ammonia molecules scattered from a gold (111) single crystal for a number of surface temperatures and incident beam energies. A molecular beam source produces a well-collimated, rotationally cold (~15 K) beam of NH3 molecules with a narrow dispersion of translational energy (~10%). The molecular beam impinges on an atomically clean, single crystal of gold (111) and the scattered NH3 is detected in a quantum-resolved manner using two-photon resonant, three-photon ionization [1].
LIDAR In-Space Technology Experiment
Authors: Nelms Richard R.
Published: February 2023

The LIDAR In-Space Technology Experiment (LITE) is a multimission Space Transportation System (STS) program to evaluate the capability of a lidar experiment to make measurements of aerosols and other atmospheric parameters from a space platform.
Optically Significant Cirrus Clouds may be Rendered "Invisible" to Space-borne Simple Lidar Systems
Authors: Grund C. J. , Eloranta E. W.
Published: February 2023

Recently, there has been much discussion among lidar researchers concerning the infinite solution set of extinction profiles which can be produced from a given simple-lidar backscatter profile1. This ambiguity is caused by the measured backscatter signal dependence on both the backscatter cross section and on the profile of extinction. Simple lidar systems produce only one measurement from which to deduce these two range-dependent parameters. Thus, simple lidar measurements must be augmented by additional measurements or knowledge of the physical relationship between backscatter and extinction before meaningful profiles of extinction can be produced. One simple lidar retrieval method assumes independent knowledge of extinction at at least one range and an assumed relationship between the backscatter cross section and extinction2. A second method seeks a common solution to several simple lidar profiles produced by observations at different viewing angles3,4,6.
Sodium Lidar Measurements of the Seasonal and Nocturnal Variations of the Gravity Wave Vertical Wavenumber Spectrum
Authors: Senft Daniel C. , Gardner Chester S. , Liu Chao H.
Published: February 2023

A method for computing the gravity wave vertical wavenumber spectrum and rms wind velocity from the data obtained by a sodium lidar system is described. The spectral slope and rms wind velocity temporal and altitude variations are determined.
Investigation of the Photosynthetic Process by Lidar Fluorosensors
Authors: Castagnoli F. , Cecchi G. , Pantani L. , Radicati B. , Romoli M. , Mazzinghi P.
Published: February 2023

Chlorophyll plays a fundamental role in the photosynthetic process of living plants, it is therefore obvious that each phenomenon related to chlorophyll may also be related to the photosynthetic process. Since chlorophyll a shows a strong fluorescence emission in the wavelength region between 67 0 nm and 740 nm it is attractive to analyze the potential of laser fluorosensors in the remote sensing of living plants. While a quite large number of papers were devoted to the lidar remote sensing of chlorophyll fluorescence in phytoplancton only few papers has been devoted to the remote sensing of chlorophyll fluorescence in living plants. A research program in this field was started as a part of a national program on agriculture improvement (IPRA Project), the analysis was carried out in the laboratory by means of a lidar simulator and in fields by means of the lidar fluorosensor FLIDAR-2.
Optimization of Lidar Boundary Layer Height Retrieval
Authors: Palm Stephen P. , Spinhirne James D.
Published: February 2023

A highly significant application for lidar sounding of the atmosphere is the retrieval of the height of the planetary boundary layer (PBL). The PBL height is an important factor in the transport of energy from the surface to the free troposphere and is directly related to the initiation and development of mesoscale events. Thus PBL height is a very useful input and validation parameter for Global Circulation Models. Currently there is no effective passive retrieval technique for PBL height. However the detection of PBL height from lidar aerosol scattering has been widely demonstrated. A primary consideration for lidar PBL height retrieval is the minimal detectability in terms of either atmospheric scattering structure or lidar system signal to noise sensitivity. Global measurements of PBL height from space borne lidar systems are envisioned. A primary consideration is how reliably PBL height may be detected for given lidar system parameters. The cost of a space borne system may be significantly reduced by minimizing telescope size and transmitted laser power.
Remote Sensing of Refractive Turbulence with Optical Spatial Filters
Authors: Churnside James H.
Published: February 2023

If a point source of light is allowed to propagate some distance through atmospheric turbulence, it will generate a random pattern of irradiance containing a wide range of spatial scales. Similarly, if an extended light source is viewed through atmospheric turbulence by a point detector, the irradiance at the detector will vary as if the extended source was a random pattern containing a wide range of spatial scales. These phenomena can be analyzed by assuming that light scattered by each scale size of refractive fluctuations in the atmosphere at each position along the propagation path reaches the observation plane with no perturbations from refractive fluctuations at other scale sizes or path positions. This analysis will be valid as long as the path-integrated turbulence is low and saturation of scintillation can be neglected.
Improved Diode-Laser Random-Modulation CW Lidar
Authors: Baba Hiroshi , Sakurai Katsumi , Takeuchi Nobuo , Ueno Toshiyuki
Published: February 2023

Diode laser (DL) has the advantages such as compact size, small weight, small consumption power, low driving voltage, high power efficiency, easy handling of power and frequency modulation, long lifetime and low cost. Although the peak power is much smaller than that of the giant pulse solid-state laser (more than eight orders of magnitude), the average power is not so small. So the use of a cw-DL realizes a compact, reliable, practical, portable lidar system. Introducing the pseudo-random-modulation technique, we already reported the construction of a DL random-modulation cw (RM-CW) lidar and the successful operation of the nighttime aerosol measurement1),2). In this paper, we report the outline of the RM-CV lidar, the improvement of the DL RM-CV lidar, and the measurement of the daytime aerosol profile measurement as well as the nighttime one.
The Leandre Project : A French Airborne Lidar System For Meteorological Studies
Authors: Pelon J.
Published: February 2023

An airborne lidar system for meteorological studies is beeing developed in France by the CNRS (Service d'Aéronomie, Laboratoire de Météorologie Dynamique -J. Pelon and P. Flamant principal investigators-, and Institut National des Sciences de 1'Univers -M. Bourdet project manager-) and the CNES. It will be implemented on board the French Research Airplane, a Fokker F27, which will be also instrumented with numerous in situ sensors.
Lidar Measurement of Boundary Layer Parameters
Authors: Eloranta Edwin W.
Published: February 2023

Atmospheric boundary layer air flows are organized by a variety of circulation patterns such as thermals, longitudinal roll vortices, and gravity waves. Studies of these structures are made difficult by the large range of spatial and temporal scales represented in these structures. Spatial scales vary from a centimeter for the smallest turbulent eddy to tens of kilometers for a cloud street circulation. Early morning thermals have typical dimensions which are smaller than 100 meters; during the the day these cells grow to sizes on the order of 2 kilometers. The lifetime of a typical cell ranges from a few minutes to the order of an hour. The overall structure of the boundary layer evolves with the diurnal cycle while the structures inside are swept rapidly along by the wind. While much has been learned about these circulations with aircraft and other traditional measurement techniques, active remote sensors such as radar and lidar are required to provide complete description of the evolving three dimensional structure.
Lidar Moisture Measurements During COHMEX
Authors: Melfi S. H. , Whiteman David , Ferrare Richard
Published: February 2023

Water vapor is one of the most important state variables of the atmosphere. Its concentration and distribution with height influences atmospheric circulation and dynamics, and figures prominently in a number of atmospheric processes including: 1) atmospheric stability, 2) cloud formation, 3) radiative transfer, 4) storm development, to mention only a few.
Imaging Bistatic Lidar Technique for Upper Atmosphere Studies
Authors: Welsh Byron , Gardner Chester S.
Published: February 2023

The structural characteristics of the sodium layer are of considerable interest in the study of mesosphere dynamics. Much of the past and current research of the sodium layer have made use of monostatic lidar measurements to study these characteristics. An alternate approach is to use a bistatic lidar configuration, consisting of a cw laser to illuminate the sodium layer, and an imaging system to record the laser spot created by the resonant sodium scattering. The basic idea is to infer the structural characteristics of the layer from selected profiles of the imaged laser spot.
Large Aperture Measurements of Optical Turbulence
Authors: Winker D. M.
Published: February 2023

There exists a significant body of literature, developed over the last 10 years or so, concerned with the theoretical analysis of atmospherically induced wavefront aberrations in terms of Zernike polynomial decompositions and power spectra of the Zernike modes (1-4). To date there has not been a satisfactory experimental verification of these analyses.
Textural edge extraction with an optical heterodyne scanning system
Authors: Poon Ting-Chung , Park Jinwoo
Published: February 2023

In many classes of images, some of the important features can be recognized by repetitive structures over a large region. Such a spatial feature provides useful information in image segmentation and classification. Various digital image processing schemes to extract textural information have been reported based on local operators manipulating image pixels, often to extract local statistics from images [1]. Other schemes exploiting the textural information in the frequency domain have also been investigated along with some successful demonstrations [2, 3]. In this paper, textural edge detection by bandpass filtering is considered. A simple technique for realizing the bandpass filter in a heterodyne optical scanning system is described and illustrated experimentally. Section II discusses textural edge detection by bandpass filtering in the context of textural image modeling and frequency domain filter function construction. Section III describes the optical scanning system capable of extracting the edge in the texture and presents some experimental results.
Development of Laser Heterodyne Radiometer for Monitoring Stratospheric Air Pollution
Authors: Ishizu Mitsuo , Itabe Toshikazu , Aruga Tadashi
Published: February 2023

Laser heterodyne radiometers using a CO2 laser and a Pb-salt diode laser as local oscillators have been developed for the detection of the stratospheric minor constituents. Among them, sulfer bearing compounds such as OCS and SO2 are related to the formation of the stratospheric aerosols, and they are the main concern of our study. According to a direct sampling method, the mixing ratio of OCS molecules in the atmosphere has been estimated to be 0.5 ppbv at the altitude of lower than about 20km and to decrease monotonically in the upper atmosphere. Due to the small amount of the stratospheric OCS molecules, a solar occultation measurement using a balloon-borne laser heterodyne radiometer will be required for the detection. The radiometers which are described below have been constructed for a laboratory measurement and resulted in successful detection of many absorption lines in the solar spectrum around a wavelength region of 10 um.
Diode Pumped Solid State Lasers For Remote Sensing
Authors: Byer Robert L. , Kane Thomas J.
Published: February 2023

The potential for global wind sensing from a satellite platform using laser sources and coherent Doppler radar was first proposed by R. M. Huffakerf[1]. The prospect for global remote wind sensing motivated our work at Stanford University toward the development of a solid state laser transmitter coherent radar system. The potential for coherent doppler wind velocity measurements using Nd:YAG was evaluated by Kane, Zhou and Byer in 1984[2]. That analysis showed the advantages of higher frequency coherent radar for improved backscattering and for improved depth resolution at a fixed velocity resolution.
Development of Spectral Equipment for Investigations of Atmospheric Gases
Authors: Zuev V.E. , Lopasov V.P. , Ponomarev Yu. N. , Sinitsa L.N. , Tyryshkin I.S. , Antipov A.B.
Published: February 2023

High-resolution laser spectrometers developed at the Institute of Atmospheric Optics for investigating the absorption spectra of atmospheric and atmosphere contaminating gases at 0.2 to 10 µm are reported.
Plans for an Airborne Multispectral Laser Imaging Polarimeter System
Authors: Kalshoven James E.
Published: February 2023

There has been difficulty in making effective use of the natural depolarization properties of the Earth’s surface as a parameter in land remote sensing. This arises from the problem in building a theoretical foundation upon which to interpret the data from reflected polarized solar radiation which is complicated by atmospheric effects and a diversity of viewing and phase angles. By designing an experiment that substantially eliminates the atmospheric and phase angle effects, a data base could be developed upon which theoretical models could be verified, refined, and predictions made. This is the goal of an airborne imaging polarimeter system being planned at NASA Goddard Space Flight Center.
Overview of an Advanced Lidar for an Atmospheric Temperature Profile Measurements Program
Authors: Johnson Bertrand L. , Korb C. Laurence , Flamant Pierre , Bourdet Mireille , Degnan John , Megie Gerard , Melfi S. Harvey , Schwemmer Geary , Uccellini Louis
Published: February 2023

The LASE (Laser Atmospheric Sensing Experiment) program is managed by the NASA Langley Research Center (LaRC) and is the development of a modular lidar facility which can be operated autonomously from the high altitude (60,000 feet) NASA ER-2 aircraft. Phase I of this program is the development of a lidar instrument system by LaRC to measure atmospheric water vapor profiles. Phase II (also refered to as LASE II) is the development by the NASA Goddard Space Flight Center (GSFC), in cooperation with the Centre National d'Etudes Spatiales of France, of an advanced lidar instrument system to measure temperature and pressure profiles of the earth's atmosphere. GSFC is developing the solid state (Alexandrite) laser transmitters for both phase I and phase II.
Introduction To The 100" Lidar System (MEGALIDAR)
Authors: Richmond Richard , Servaites Jan
Published: February 2023

The colossal 100" collimator facility is being developed into a lidar system. The collimator is a 12 story high chamber with a 100" diameter f/6 mirror at the bottom of the chamber. By opening the top of the facility, the collimator is converted into a vertically pointed telescope. By installing a suitable detector at the focal point of the telescope, the chamber becomes the receiver of a extraordinary lidar system. The purpose of this paper is to introduce the facility at Wright-Patterson and the efforts, both present and planned, being undertaken to make this one-of-a-kind LIDAR facility a reality.
400 Hz Line Center Stability in a GaAlAs Diode Laser
Authors: Shay T.M. , Dobbins J.D. , Chung Y.C.
Published: February 2023

Frequency-stabilized semiconductor lasers are practical sources for a wide variety of potential applications including remote sensing, laser spectroscopy, optical frequency standards, coherent optical communication, coherent optical sensors, laser gyroscopes, etc. In particular diode lasers are convenient sources for injection locking tunable solid state lasers. Solitary semiconductor lasers are essentially impervious to acoustical and mechanical disturbances since they have no external optics. On the other hand, the operating frequency of a semiconductor laser is very sensitive to temperature and current variations, therefore standard diode laser systems have very poor frequency stability. Thus the first step in frequency stabilizing a diode laser consists of stabilizing the temperature and injection current of the laser.
An Airborne Wavemeter for an Atmospheric DIAL Experiment
Authors: Goad Joseph H.
Published: February 2023

A wavemeter is being designed and developed as a subsystem to support the NASA LASE (Laser Atmospheric Sounding Experiment) ER-2 airborne project. The prime objective of this project is to use a DIAL remote sounding system with a pulsed tunable Alexandrite laser to measure vertical profiles of water vapor and aerosols. The technology to make the required wavelength centroid and wavelength profile measurements has been demonstrated by others in laboratory environments. The developmental effort in building this wavemeter is to operate within requirements inside the Q-bay environment of an ER-2 aircraft. In this environment, the temperature can vary from 15 to 40 degrees Celsius and the pressure can vary from 14.7 psi to 3.5 psi. The interferometers in the wavemeter must be isolated from this thermal and pressure variation. A thermally controlled housing and thermal vacuum chambers have been designed and brassboarded to demonstrate the required stability.
Multiphoton and Above-Threshold Ionization
Authors: Chu Shih-I
Published: February 2023

Recently a number of advances have been made regarding the developments of semiclassical Floquet theories for ab initio nonperturbative treatments of intense field multiphoton processes.1,2 These include multiphoton excitation (MPE) and dissociation (MPD) of molecules,1 multiphoton ionization (MPI) of atoms,1 many-mode Floquet theory,1,2 SU(N) dynamic symmetries and symmetry breaking,2 charge exchange in laser fields2 and nonlinear optical processes etc.3
Photoelectron Spectrum Resulted From Autoionizing State Resonance
Authors: Zhao Lee-geng , Xu Zhi-zhan
Published: February 2023

Autoionizing state resonance is very likely to occur during the above-threshold ionizations of atoms. This paper presents our theoretical studies of the photoelectron spectrum produced by such resonance. By employing the technique of resolvent operator, we have shown that in general there are four peaks in the spectrum (as shown in Fig.1), two of which result from the autoionization of the autoionizing state,[1] others are related to the photoionization of the autoionizing state.
Double Electron Excitation of Lithium by Electron Impact
Authors: Srivastava R. , Williamson W.
Published: February 2023

Excitation of the autoionizing states caused by single inner shell electron excitations in alkalai atoms by electron impact have been well studied using various approximations. These include the Born, Glauber1 and distorted wave theories.2 In lithium, in addition to single excitation, there have been some doubly excited states observed. The doubly excited states with the two electrons are the most fundamental atomic species which autoionize. Such doubly excited states in helium and alkaline earths have also been studied.3-5 A first step towards the study of such excitations in lithium would be to find the cross sections for their production by electrons. The first calculations of this nature were done by Kulander and Dahler4 using the simple Born Oppenheimer approximation. They reported results for Li(1s)2(2s)2S→Li(1s) (2p)2 4P. We reconsidered this problem in a more precise manner using the distorted wave theory. Our distorted wave calculation includes distortion of the initial and final states of the incoming and outgoing electrons separately by using different distorting potentials. We have used the static potential, the polarization of the target lithium atom as well as the exchange of the incoming electron with the bound electrons in the target. The bound states of the target are represented in initial and final states by the Hartree Fock wave functions as used by Kulander and Dahler.4 The details of the analysis, results and discussion will be presented at the conference. In Table I we briefly display our results using various versions of the distorted wave theory (Ei is the incident energy in Ry, I and F represent the inclusion of the initial and final state static potentials respectively, E and P signify the additional inclusions of the exchange and polarization potentials).
Final State Effects in Above-Threshold Ionization
Authors: Becker W. , Schlicher R. R. , Scully M. O.
Published: February 2023

With the goal in mind to separate final state effects due to the interaction of the ejected electron with the laser field from dynamical effects associated with the process of ionization, we investigate the following simple model: We assume an effective interaction that just lifts the electron into the continuum via absorption of the minimum number N of photons which is necessary to overcome the ionization potential (defined in the absence of the field). The effective interaction is left unspecified except its matrix element is assumed to be proportional to IN/2 with I the intensity of the laser field. As soon as the electron is free we assume it only feels the laser field and, consequently, is described by the so-called Volkov solution which provides an exact solution for an electron in an external plane wave field. For simplicity, we also adopt the long wavelength approximation for the laser field. For the initial atom and the final ion we take the unperturbed wave functions and we also disregard the recoil imparted to the ion. Altogether, this is essentially the Keldysh approximation. It turns out that boundary conditions, i.e. the way the electrons leaves the laser pulse, are of vital importance.1 In order to explain the experimentally observed absence of intensity-dependent shifts in the electron spectra we have to assume that the electron leaves the electron pulse on the side rather than being passed over by the pulse. Under these conditions, we also obtain the total suppression of the low-lying peaks of the electron distribution with increasing intensity which is impressively born out by recent experiments.2,3 The mechanism can be ascribed to the ponderomotive potential which adds to the ionization potential. When the electron leaves the pulse on one side the energy corresponding to the ponderomotive potential is converted into kinetic energy.4
Strong Field Laser Ionization of Model Atoms
Authors: Pindzola M.S. , Bottcher C.
Published: February 2023

Recent experiments on the ionization of atoms under strong field lasers has renewed interest in the theoretical modeling and calculation of such nonperturbative processes. A promising calculational method is the direct solution of the time-dependent Schrodinger equation using numerical techniques developed to solve parabolic partial differential equations on vector processing computers. We are currently working on numerical solutions to the one-dimensional equation (in atomic units): where V(r,t) is a finite square well potential subject to an arbitrarily strong electromagnetic field. We have used the Galerkin method with linear tent finite elements to check the one bound state results of Goldberg and Shore1 and the two bound state results of Austin2. We plan to use the Galerkin or collocation method with B-spline finite elements to investigate the one-dimensional Coulomb problem. The most favorable numerical method will be extended to two or more dimensions.
Classical Calculations of the Effects of High Brightness Laser Radiation on Photoelectron Angular Distributions
Authors: Kania Don R.
Published: February 2023

A two step model has been developed to describe the effects of a high brightness laser on the angular distributions of photoelectrons near and above threshold. The photoelectron production process and the transport of the electrons away from the ion are decoupled. The model predicts that the photoelectron distribution becomes more isotropic as the laser intensity increases. A larger laser intensity is required to perturb higher energy photoelectrons.
Collective Dipole Exitation of Many-electron Atoms by Intense Laser Pulse
Authors: Faisal Farhad H.M.
Published: February 2023

A major implication of the remarkable data/1-3/ on multiple ionization of many electron atoms in intense laser pulses is the unusually strong coupling strength at UV and infrared frequencies. Luk et al./2/ appear to have been the first to envisage a giant dipole or multipole excitation of atoms, in the present context. The purpose of this paper is to give a many-body non-perturbative analysis (using a generalization of a method of Tomonaga/4/ within the random phase approximation) of an N-electron atomic Hamiltonian coupled to a laser pulse and to demonstrate the existence of laser driven colletive dipole excitations of noble gas atoms. We also determine the photon absorption cross-sections due to this process. It is shown that the dipole operator of a many-electron atom can execute quantum oscillations with a distribution of fundamental frequencies and that the laser excites preferentially the mode whose frequency is resonant with the laser frequency. These modes appear essentially in the outer region of the atomic charge distribution, both at 193 nm and 1064 nm laser wavelengths. It is found, for example, for Xe that the 5p6 and the 5s2 sub-shells alone contribute virtually completely to the resonant modes; all the other shells contributing less than 0.1%.
The England/Holland Halo Display of Easter Sunday 1974
Authors: White Richard
Published: February 2023

Halos of unusual radii were seen in parts of southern England and in Holland in April 1974. This presentation is concerned with the phenomena observed in England on the evening of (according to most accounts) Easter Sunday 14 April 1974, from 1730hrs-1855hrs GMT. The most interesting feature of the display in that period was the variation of brightness around the circumference of the halos, which appeared to be due to the presence of incipient arcs of contact. The present investigation is an attempt to represent these features interms of crystal sub-types and/or orientations.
Temperature Profiles Computed From Superior Mirage Observations
Authors: Lehn Waldemar H.
Published: February 2023

The superior mirage is seen under conditions of temperature inversion. If the vertical atmospheric temperature profile is known, the computer simulation of such observations is relatively straightforward1; but in most cases the necessary information is not available. However, with suitable assumptions, this distribution can be deduced from the mirage of a known object.
Blue Skies, Red Sunsets, and the Green Flash
Authors: Greenler Robert
Published: February 2023

Many beautiful sky effects can be easily seen that result from light scattering in the atmosphere. Slides are shown to illustrate many of these effects and several scattering demonstrations help explain the mechanisms.
Solar almucantar radiance and aerosol scattering; some results at one tropical and two mid-latitude stations
Authors: Oluwafemi C.O.
Published: February 2023

The data base of this presentation consists of 36 sets of sky radiance and solar irradiance observations: 15 sets for Lagos (long. 3.3°E, lat. 6.3°N), 17 sets for Kensington, Sydney (long. 151°E, lat. 34°S) and 4 sets for Bedford (long. 72°W, lat. 43°N), MA, USA. As all the observations were made using the same apparatus at various times by the same person, instrumental and human inaccuracies are about constant and data from different stations are reliably compared.
The Imaging Properties of Rarefied Clouds
Authors: Shubert R.
Published: February 2023

Rarefied clouds of dust and gas, such as occur in comets for example, may exhibit under certain conditions of illumination a wide variety of bright morphological features which are also characteristic of optical imaging. Very similar effects are observed to occur in the phenomena of atmospheric optics, with respect to both the morphology of the light patterns which are produced and their temporal behavior.
Optics of Sunbeams
Authors: Lynch David K.
Published: February 2023

Shadows of clouds on the atmosphere go by a variety of names: solar rays (sunbeams, sun drawing water) occur when the sun is above the horizon and crepuscular rays (Rays of Buddha, Ropes of Maui) occur when the sun is below the horizon. In this paper the observational properties of such rays are summarized and used as a guide for interpreting the theoretical analyses.
A Possible Application of the Fraunhofer Line Filling-in Effect to Cloud Top Height Measurement
Authors: Park H. , Heath D. F. , Mateer C. L.
Published: February 2023

A feasibility of a new technique to measure the cloud top height is demonstrated. This technique utilizes the Fraunhofer line filling-in effect in the atmospheric scattering.
The Catastrophe Optics of Atmospheric Twinkling and Reflections from Rippling Water
Authors: Berry Michael
Published: February 2023

What I aim to show is that a large and varied class of natural optical phenomena can be understood in a unified way with the aid of one concept: the caustic. This is an idea from geometrical optics but its usefulness is not restricted to that approximation.
Surface Raman Spectroscopy Without Enhancement
Authors: Campion Alan
Published: February 2023

I will describe recent experiments that demonstrate our ability to observe Raman scattering from molecules adsorbed on single crystal surfaces without requiring either surface or resonance enhancement. I will discuss the details of the experimental method, relevant selection rules, information obtainable from the angular distribution of the scattered radiation and some implications of our experiments regarding the mechanism of surface-enhanced Raman scattering. To illustrate the versatility of our method, examples will include studies of molecules adsorbed on metal and semiconductor surfaces in ultrahigh vacuum, in the presence of reactive gases at high pressures and in the electrochemical environment.
Photodesorption and Adsorbate-Surface Interactions Stimulated by Laser Radiation
Authors: Chuang T. J.
Published: February 2023

Laser photons can interact with a gas-solid system to promote heterogenous reactions and to stimulate desorption. Two classes of photon-enhanced surface processes have been extensively investigated in recent years. The first one involves laser-induced adsorbate-surface reaction and desorption resulting in the chemical etching of the solid. The examples include the halogen reactions with silicon and metals affected by ultraviolet and visible photons. Recent time-resolved mass spectrometric studies in conjunction with ESCA, Auger spectroscopy and thermal desorption measurements have revealed interesting surface reaction dynamics and etching mechanisms. The second one involves infrared laser photodesorption initiated by excitation of internal molecular vibrations. Recent studies of the desorption phenomenon for molecules adsorbed on both dielectric and metal surfaces excited by the infrared radiation will be discussed. The photo-excitation process, including both single and multiple photon absorption and the various vibrational energy transfer and relaxation processes related to photodesorption, will be examined with particular emphasis on assessing the quantum and thermally-assisted effects. A review on both classes of laser-stimulated surface processes will be given.