bluuebunny/crossref_metadata_2025 huggingface dataset:
Bright Picosecond Thermal Continuum X-Rays from Intense Sub-Picosecond Laser-Plasma Interactions
Authors: Umstadter D. , Workman J. , Maksimchuk A. , Liu X. , Ellenberger U. , Coe S. , Chien C.-Y.
Published: February 2023

Short-pulse high-intensity lasers interacting with solid targets make possible the study of a new class of plasmas.1 They are unique because during the ultrashort laser pulse relatively little expansion occurs and the density scale length remains much less than the laser wavelength. This makes possible the deposition of a significant amount of the laser energy at densities much greater than the critical density, which is then efficiently converted into heat, ionization, and subsequently x ray emission, either through de-excitation or recombination. The x-ray pulse will be extremely bright because of the high density, the small dimensions of the laser spot size, and the ultrashort x-ray pulse width. The latter is due to rapid cooling by expansion and diffusion, which results from the steep temperature and density gradients, and the high collision rates at high density. These bright compact ultrashort- pulse x-rays have applications in time-resolved diffraction, holography, spectroscopy, microscopy or radiography studies of transient biological or physical phenomena.
Resonant High-Intensity Picosecond X-Ray Generation; Thin Films Usage Advantages
Authors: Savel’ev A.B. , Dzjidzjoev M.S. , Gordienko V.M. , Kolchin V.V. , Magnitsky S.A. , Platonenko V.T. , Tarasevitch A.P.
Published: February 2023

Femtosecond laser-induced plasma has proved to be the powerful source of short pulses of incoherent soft X-rays with energy from 50 ev up to few keV and even harder [1,2]. Extremely short X-ray pulse duration down to 1 ps makes it possible to use this radiation in time-resolved X-ray diagnostics of ultrafast processes (X-ray diffraction, spectroscopy, microscopy). It is of special interest to design X-ray microscope in so-called “water window” region to investigate living cells. One more advantage here is as shorter X-ray pulses are used less information recorded is deteriorated by damaging of an investigated cell by X-rays. To generate X-rays above 200 eV intensities of 1015– 1016 W·cm−2 and even higher have to be used. As it was shown previously [3] large amount of X-ray energy emitted from femtosecond plasma consisting of light atomic elements (B,C etc.) is radiated from resonance transitions of highly stripped ions. In the case of carbon target the most bright lines of H- and He-like C ions lie in the “water window” region. The main goals of our research are to find “optimal” conditions for generating powerful few-picosecond X-ray pulses in the vicinity of “water window” region by femtosecond laser pulses with rather low intensities 1015– 1017 W·cm−2 and to investigate whether it is possible to increase electron temperature of the plasma and to generate few keV X-rays by using thin targets.
Observation of Forward Raman Scattering and Energetic Electrons in High Intensity, Sub-Picosecond Laser, Underdense Plasma Interaction Experiments
Authors: Coverdale C.A. , Darrow C.B. , Hammel B.A. , Mori W.B. , Decker C. , Tzeng K.C. , Joshi C. , Clayton C.
Published: February 2023

Many theoretical and computer simulation results have been published recently involving the interaction of short pulse, high intensity lasers with underdense plasmas.1-4 This is a new regime in which to study laser-plasma interactions since the length of the laser pulse is shorter than the Rayleigh range of the laser and the length of the plasma (cτL< LR, Lp). Developments in laser technology over the last several years have made the experimental investigation of this regime possible. In this paper, we describe the first experimental observation of forward stimulated Raman scattering and energetic electrons from the interaction of a subpicosecond, high intensity laser with an underdense plasma.
Two-colour phase control in tunneling ionization and harmonic generation by a strong laser field and its harmonics
Authors: Kondo K. , Nabekawa Y. , Watanabe S.
Published: February 2023

Multiphoton processes in a strong optical field, such as ionization and harmonic generation, have attracted both experimental and theoretical interest in recent years. In the tunneling ionization regime, a very simple physical picture called a two step model or a returning electron model[1,2], fairly well predicts the general aspects of such important phenomena as non sequential double ionization and the cutoff of high-order harmonics. This model straightforwardly predicts not only the enhancements of high-order harmonics and of ion yield but also the extension of the cutoff-order of harmonics when two optical fields of different frequencies are coherently superimposed.
Above-Threshold Ionization Beyond the High Harmonic Cutoff
Authors: Yang Baorui , Walker B. , Sheehy B. , DiMauro L. F. , Agostini Pierre
Published: February 2023

Over the last few years, strong-field physics has advanced to a state that quantitative tests of theoretical models are now possible experimentally[1-3]. This is particularly important to identify the universality of all strong-field effects, such as above-threshold ionization (ATI), high optical harmonic generation (OHG), and multiple ionization. In this talk, we will report on the progress of high sensitivity electron and ion measurements in the high field limit on inert gas atoms and helium. The experiments are performed with kilohertz laser systems operating at 1 μm and 0.78 μm with 50 ps and 0.1 ps pulse durations, respectively and extend from 1012–16 W/cm2. Thus, the studies are capable of examining the full dynamic range of field interactions from multiphoton to tunnel ionization. Critical comparison to both time-dependent quantum mechanical calculations using a single electron approximation (SAE) and quasi-classical models provide interesting insights into the underlying physics.
Optimal quasi-phase-matching for high-order harmonic generation in gases and plasma
Authors: Shkolnikov P. L. , Lago A. , Kaplan A. E.
Published: February 2023

High-order harmonic generation (HHG) [1], if phase matched, may provide an important and convenient (in principle, table-top) source of short-wavelength coherent radiation. So far, however, HHG phase matching remains poor. The only experimental way to improve HHG phase matching has been weaker focusing of the pumping beam. An inherent disadvantage of this method is that it lowers the incident intensity thus decreasing overall power conversion efficiency. Moreover, this technique can have only a limited success in approaching the optimum phase matching which corresponds to large negative values of the parameter bΔk (b is the laser confocal parameter, and Δk is the dispersive phase mismatch of the medium), since in gases or, to much larger extent, in plasma, Δk is positive. Recently, J. M. Rax and N. J. Fish [2] have suggested plasma density modulation as a method to phase match relativistic third-harmonic generation in plasma. Their idea is essentially a ramification of the well known in nonlinear optics method of quasi-phase-matching (QPM). Almost all the effort in QPM has been concentrated on the second-harmonic generation in solids since obviously much more convenient ways to optimize higher-order harmonic generation (until recently -- almost exclusively, third-harmonic generation) in gases exist. As a result, to the best of our knowledge, no general consideration of quasi-phase-matching in gases and plasma, in particular for HHG, has been published yet. In the present paper, we consider quasi-phase-matching of HHG by a focused beam in plasma or a gas whose nonlinear succeptibility and refractive index are spatially modulated, in particular through the medium density modulation, and demonstrate that QPM is feasible with the available laser and plasma technology. In accordance with the HHG experimental conditions, we assume that harmonics are generated by bound electrons. To obtain analytic results, we rely on the perturbation expressions for the induced nonlinear polarization; our results remain valid beyond perturbation limits if some general assumptions hold regarding nonlinear polarization induced by strong laser field [3]. Accurate quantitative estimates of the improvement in HHG due to QPM requires nonperturbative calculations of HHG in homogeneous media with large negative bΔk; to our knowledge, no such calculations have been published yet. On the basis of a nonperturbative model introduced in Ref. [4], however, one might expect QPM-optimized harmonic intensity to be up to two order of magnitude larger, with available depth of plasma density modulation, than the output intensity attainable under currently employed loose focusing and poor phase matching. Even more important a consequence of QPM is the opportunity to use tight focusing so far deleterious for HHG; resulting much higher intensities would greatly increase power conversion efficiency as compared to the loose-focusing regime.
Experiments with Short-Wavelength Lasers Driven by Ultra-Short Pulse, High-Intensity Lasers
Authors: Donnelly T.D. , Glover T.E. , Lipman E. A. , Hofer M. , Falcone R.W. , Da Silva L. , Morwka S. , Eder D.C.
Published: February 2023

A multi-terawatt laser was used to generate and characterize plasmas appropriate for recombination pumped x-ray lasers. Thomson scattering was used to determine the electron and ion temperatures on a sub-picosecond time-scale. A recombination pumped x-ray laser on the Lyman-alpha transition of H-like lithium was also studied.
Femtosecond Laser Interaction with High-Density Gas Jets
Authors: Stenz C. , Brückner R. , Blasco F. , Amiranoff F. , Malka V. , De Wispelaere E. , Bonadio R. , Audebert P. , Geindre J.P. , Gauthier J.C , Dos Santos A. , Rey G. , Mysyrowicz A. , Antonetti A.
Published: February 2023

The propagation of an intense and ultrashort laser pulse in a high pressure gas may be strongly modified because of the fast ionization induced by the intense optical field (1). The fast evolution of the ionization rate of the gas during the laser pulse induces both blue-shifting of the transmitted laser spectrum and strong self-defocusing of the laser beam (2).
Theory and Experiment for Photoelectron Spectra in Short-Pulse High-Intensity Ionization
Authors: Reiss H. R.
Published: February 2023

Recent experiments[1] designed to give high-resolution spectra for photoelectrons ionized from helium by a short-pulse laser at very high intensity, have been matched by theory[2] to within the experimental error bounds for all but the lowest part of the energy spectrum. This is notable for several reasons. First, no other comparison of high intensity theory and experiment has previously been shown to be in such close and detailed correspondence. Second, the experimentalists, in their attempts to match theory and experiment had come to the conclusion that no existing theory could duplicate the energetic, or “hot” end of the electron spectra. This is now shown not to be at all a source of difficulty. Finally, the theory employed [3,4] is one which has long been asserted to be valid for atomic ionization as long as certain minimum intensity criteria are met. Previous published “tests” of the theory have failed by large factors to satisfy the required applicability criteria, but the present experiments do satisfy them, and confirm the validity of the theory for very strong fields.
Laser Induced Fluorescence Probing of Highly Vibrationally Excited Acetylene: Vibrational State Mixing in the Ground and Electronically Excited States
Authors: Crim F. Fleming
Published: February 2023

Vibrational overtone excitation and laser induced fluorescence detection identify the mixing of vibrations in the ground electronic state and determine the vibrational structure in the excited state, including the frequencies on all the ungerade vibrations.
The Deconvolution Method Used In The Analysis Of a-C Raman Spectrum
Authors: Wang Qi , Allred D. D.
Published: February 2023

It is believed that the Raman spectrum of amorphous carbon (a-C) is a kind of broadened version of the phonon density of states (PDOS) of graphite1. To further verify this relation and to extract more information from the Raman spectrum of a-C, we introduce the deconvolution method into the analysis of a-C Raman spectrum.
Carbenes in the Interstellar Gas
Authors: Thaddeus Patrick
Published: February 2023

Carbenes are a significant trace constituent of the gas in the interstellar medium (and in the expanding shell around at least one star), representing about one-sixth of the molecular species that have been identified in space. The identification of one of the most abundant and widespread interstellar carbenes, the cyclopropenylidene ring, C3H2, is described, together with recent laboratory work on the excited vibrational states of this molecule and on the geometrical structure of one of its isomers, the carbon chain carbene H2C3. A number of additional free carbines which might be detected in space are considered. There are at least two reasons why carbenes are comparatively conspicuous in astronomical sources relative to other reactive molecules: one is their high polarity; a second is their production via the same ion-molecule reactions that make known stable species in space (or very similar reactions). Finally, it is pointed out that cumulene carbon chains somewhat longer than those so far detected in space are promising candidates for the carriers of the interstellar optical diffuse bands.
Near-threshold structure of molecular hydrogen at the 1s + 2l dissociation limit
Authors: Eyler E.E. , Catching B.F. , Melikechi N.
Published: February 2023

High-resolution measurements of molecular structure very near a dissociation limit can be used both to probe long-range atomic interactions and to make accurate determinations of dissociation energies. Our research group has investigated the H(1s) + H(2s or 2p) dissociation limit in molecular hydrogen using optical double resonance with single-mode lasers. Fig. 1 shows the general scheme of the experiment. Our measurements of bound states in H2, reported in Ref. 1, have now been extended to include the adjoining continuum and the other stable isotopomers, HD and D2. The most weakly bound levels to which transitions are seen are bound by only about 0.03 cm−1, equivalent to about 40 mK. Very sharp continuum resonances are also observed in the region just above threshold.
Infrared Fourier Transform and Diode Laser Spectra of Formaldoxime
Authors: Bannai R. , Duxbury G.
Published: February 2023

The infrared spectrum of the simplest oxime, CH2NOH, was first obtained at low resolution in the gas phase by Califano and Lüttke1. Subsequent high resolution spectroscopy by Duxbury el al.2 and by Duxbury3 demonstrated that although the original vibrational analysis was correct, the directions of the transition moments derived fro from the analysis of low resolution band contours were not.
Perturbative Nearly-Degenerate Four-Wave Mixing Lineshapes in Gases
Authors: Rahn Larry A.
Published: February 2023

Nearly-degenerate four-wave mixing (NDFWM) spectroscopy1 and the closely related tunable-laser-induced grating spectroscopies2 have proved to be valuable tools in the study of nonlinear optical interactions. The NDFWM spectral lineshape provides information concerning the lifetimes,3 and therefore the identities, of multiphoton scattering mechanisms. In addition to the great number of investigations in liquids and solids, considerable research has focused on wave-mixing in resonant atomic gases for phase conjugation applications.4 Although many special cases have been discussed, general expressions that include the effects of molecular motion for the NDFWM lineshape in gases have not been previously reported. The present study is motivated by an interest in understanding the mechanisms contributing to degenerate four-wave mixing (DFWM) spectroscopy in molecular gases for application to combustion and chemical physics research.
Time-Resolved Probes of Adsorbate-Substrate Energy Transfer
Authors: Germer T.A. , Stephenson J.C. , Heilweil E.J. , Cavanagh R.R.
Published: February 2023

Recent advances in time-resolved measurement techniques have provided new molecular level insights into energy transfer processes. Through pump-probe measurements of excited state recovery, direct measurements of lifetimes and energy transfer pathways have been achieved. In vapor, liquid, and condensed phase studies, these techniques have provided the capability of following the evolution of molecular processes. Application of similar techniques to clarify the timescales and pathways for energy transfer processes at surfaces is only now beginning to meet with success.1,2
The Very High Resolution Spectrometer at the National Institute of Standards and Technology
Authors: Fortna John , Morgan Harry , Seyoum Hailemichael , Humm David C. , Furst Mitchell L. , Hughey Lanny R.
Published: February 2023

Of seven very high resolution spectrometers in the United States and Japan, two utilize electron storage ring light sources and provide photoelectric scanning of the vacuum ultraviolet spectrum.1 These are the 6.65 m off-plane Eagle instrument connected to the Synchrotron Ultraviolet Radiation Facility storage ring at the National Institute of Standards and Technology (NIST)2,3 in Gaithersburg, Maryland, and the other is a similar instrument connected to the synchrotron at the Photon Factory in Tsukuba, Japan. The NIST spectrometer (Fig. 1) uses a 4800 l/mm gold-coated spherical mirror grating blazed at 900 Å with a radius of curvature of 6.65 m and a ruled area of 125 mm × 110 mm. The spectrometer uses this grating in the first order and at present has a full width half maximum resolution of ~10m Å and uses horizontal slits.
Tutorial on Algorithms for 3D Properties of Materials that Bend Rays
Authors: Vest Charles M.
Published: February 2023

Summary not available.
Application of Computed Tomography to Oil Recovery from Porous Media
Authors: Gryte Carl C. , Wang S. Y.
Published: February 2023

CT has been demonstrated to produce quantitative images of oil/water distributions within the cross sections of sandstone such as that found within oil producing reservoir materials (1). The oil fraction of each image element is computed (2) from a comparison of a core containing oil and water (experimental core) with two reference cores (one containing only oil and a second containing aqueous KI (all aqueous phases were traced with 1 molar KI)). This oil fraction is the fluid composition that occupies the void spaces within the sandpack. Figure 1(a-d) illustrates the components of the oil fraction image.
Reconstructing Discontinuities in Multidimensional Inverse Scattering Problems: Smooth Errors Versus Small Errors
Authors: Beylkin Gregory
Published: February 2023

Many practical problems of non-destructive evaluation can be solved provided we can accurately reconstruct discontinuities of the parameters of the physical medium. Seismic exploration, medical applications, crack and void detection are examples. Our concern is a mathematical formulation of the linearized inverse scattering problem, so that we can

i. obtain explicit algorithms

ii. prove that, indeed, the discontinuities are recovered.

Adopting the point of view standard in the theory of pseudodifferential operators we note that, in general, it is impossible to construct an explicit solution (say the Green's function), but a parametrix can often be obtained explicitly. The parametrix is a solution which is defined exactly as the Green’s function except that an arbitrary smooth function may have been added to the source term of the equation (see [1], for example). Mathematicians have been using these solutions to gain insight into the properties of the partial differential equations. In dealing with the problems of nondestructive evaluation, we can make use of these solutions to obtain algorithms for reconstructing the discontinuities of parameters describing the medium [2].
Some results on the use of local basis functions for reconstruction representation in computed tomography
Authors: Wecksung George W. , Hanson Kenneth M.
Published: February 2023

In computed tomography (CT) as well as other areas of digital image processing, a discrete representation of a function of two variables on a continuous domain is needed. One approach is to specify the values of the function on an equally spaced grid and interpolate for intermediate values. A more general approach Is to represent the function as a linear combination of basis functions [1,2]. Iterative CT algorithms, e.g., ART, require repeated evaluation of line or strip projection integrals over a trial object function (reconstruction). If the first representation is selected, then we must get interpolated values in order to perform the integration. The interpolation can be performed in a variety of ways; each way makes implicit use of a set of basis functions. If nearest-neighbor interpolation is chosen, the resulting set of basis functions are square pixels centered on the sample points. For bilinear interpolation we get a bilinear tent function and for band-limited interpolation we get a product of separable sine functions with zeros at all sample points but one.
Picosecond Studies on Phase and Energy Relaxation of Excitons in Semiconductors
Authors: Masumoto Yasuaki
Published: February 2023

Picosecond relaxation processes of excitons are extensively studied in CuCl, CdSe and GaAs-AlAs MQW (multi-quantum well structures) by means of time-resolved induced absorption, luminescence and non-degenerate four-wave mixing. We have applied the picosecond time-resolved induced absorption and luminescence measurements to excitons in CuCl, CdSe and GaAs-AlAs MQW (Fig. 1). 1-3) Aside from the typical nature of Wannier excitons in CuCl, excitons in CdSe and GaAs-AlAs MQW have distinct characters, such as strong piezoelctricity and two-dimensional disorder. The analysis of the experiments derives the distribution of excitons in the two-dimensional energy-time coordinates. Thus, energy relaxation processes of excitons in a variety of semiconductors are clearly visualized. Prior to energy relaxation, coherently generated excitons are considered to be dephased. Phase relaxation of excitons in CuCl is directly measured for the first time in the picosecond time domain by means of time-resolved non-degenerate four-wave mixing (Fig.2).4) These new techniques will be demonstrated and the dephasing as well as energy relaxation mechanism of excitons and excitonic polaritons will be discussed.
Time-Resolved Study of Resonant Secondary Emission in NaNO2 Crystal
Authors: Murata Hiroshi , Kobayashi Toshihiro , Kato Riso
Published: February 2023

NaNO2 crystal shows multiple order Raman scattering due to v2-vibration of

NO

2
−

when excited near the zero-phonon line at v00(3848.9A) of the singlet absorption (1A1 → 1B1).1) We have studied the resonant secondary emission in highly purified NaNO2 crystal by nanosecond time-resolved measurements.
The Analysis of Excitation Dependent Luminescence Spectra by Total Luminescence Spectroscopy
Authors: Suter G.W. , Kallir A.J. , Wild U.P.
Published: February 2023

In Total Luminescence Spectroscopy (TLS) the luminescence intensity is recorded as a function of both the excitation and the emission frequency, yielding a two-dimensional spectrum (TDS)

 I

lum

 

(

v
˜

ex

,

v
˜

em

)
Investigations of the luminescence of N-alkenylcarbazoles and their charge-transfer complexes with 2,4,7-trinitro-9-fluorenone and 7,7,8,8-tetracyanoquinodimethane
Authors: Janowski Andrzej , Rzeszotarska Jadwiga , Makulski Włodzimierz , Ranachowski Jerzy
Published: February 2023

The effect of the quencher and length of the carbon chain on fluorescence quenching of N-alkenylcarbazoles with 7,7,8,8-tetracyanoquinodimethane (TCNQ) and 2,4,7-trinitro-9-fluorenone (TNF) was investigated. During quenching the maxima of fluorescence for N-vinyl-, N-allyl-, N-pentenyl-, and N-hexenylcarbazole, similar to each other, are slightly shifted towards higher wavenumbers. Qeunching of the carbazoles is also similar. However, it differs considerably for TNF and TCNQ, the differences having both qualitative and quantitative character. The fluorescence intensity of the carbazoles is almost equal to zero at the carbazole:TCNQ concentration ratio 1:1 whereas in the case of TNF a large excess of the quencher is needed. The quenching factor, both for TCNQ and TNF, increases with increasing carbon chain length. The quenching factor for TCNQ is almost of an order of magnitude higher than for TNF. This is due to higher electron-acceptor properties of TCNQ, compared with TNF, since the quenching is associated with formation of charge-transfer complexes.
Thermally Stimulated Luminescence of Irradiated Caffeine
Authors: Jahan M.S. , Cooke D.W.
Published: February 2023

This study is part of a continuing investigation of the factors which affect radiation damage in methylxanthines, which are of immense biomedical importance. In order to gain knowledge regarding charge trapping mechanisms in caffeine (1,3,7-trimethylxanthine) we employed the well-known technique of thermally stimulated luminescence (TSL) and investigated the system in the temperature interval 77 - 300 K.
Deactivation of Excited States of Liquid Alkyl Benzenes at the Entrance Window
Authors: Sasson R. , Weinreb A.
Published: February 2023

In a series of early investigations(1) a marked decrease of the fluorescence quantum yield of liquid alkyl benzenes (e.g. toluene, mesitylene) was found when the wavelength of the exciting radiation was decreased from those for excitation of S1 (the first excited singlet level) to those for excitation of S2 and S3 (the second and third excited singlet levels). Further decrease of the excitation wavelength is accompanied by an increase in the fluorescence quantum yield. These results for toluene are reproduced in Fig.1, curve(a), where Φλ represents the fluorescence intensity for excitation at wavelength λ. The low value of Φλ for excitation of S3 may be caused either by a quenching mechanism which acts on the molecule in this state, or by a non-efficient transition from this state to the emitting state S1, or by some quenching mechanism which acts on the molecule in S1 but which is absent when S1 is directly excited from the ground state. (A combination of all three mechanisms or any two of them is, of course not excluded).
Exchange Interaction and Oscillator Strength in Neutral Bound Exciton
Authors: Staszewska G. , Suffczyńskit M. , Ungiert W. , Wolniewicz L.
Published: February 2023

In an exciton bound to a neutral donor the electron-hole exchange interaction mixes states of opposite symmetry with respect to the interchange of two electrons [1]. We take a perturbation parameter proportional to the electron-hole exchange integral and use a variational-perturbation method to compute wave function in the first order and the ground state energy in the second order. The basis functions of Page and Fraser with nonlinear parameters of Stebe and Munschy [2] and reoptimized scale parameter for each electron-to-hole mass ratio, practically reproduce the best ground state energy, and are used to compute the linear combinations for the envelope function corrections symmetric and anti-symmetric with respect to interchange of two electrons. The electric dipole moment of the exciton radiative recombination is proportional to overlap integral of the envelope and the donor ground state wave function. Squared overlap integral gives the ratio of the bound exciton to the conduction-band-to-valence-band transition. The Page-Fraser 70-term envelope function and the correction due to electron-hole exchange interaction with the exchange integral taken from the free exciton singlet-triplet splitting [3], lead to agreement of the calculated oscillator strength for bound exciton recombination with the measured radiative lifetime of bound excitons in wurtzite type semiconductors CdS [4] and CdSe.
Multiple LO phonon scattering in indium bromide
Authors: Yoshida Masashi , Watanabe Hideo , Ohno Nobuhito , Nakamura Kaizo , Nakai Yoshio
Published: February 2023

Multiple scattering lines of Raman forbidden LO phonon (ħωLO = 16meV) have been observed in orthorhombic InBr by the excitation above the direct exciton energy (Ex=2.331 eV).1) Scattering spectra are characterized by the intensity alternation that even numbered lines are stronger than odd numbered lines. In the present study incident photon energy dependence and temperature dependence of multiple LO phonon lines are investigated to clarify exciton relaxation mechanism in polar semiconductor with inversion symmetry and the origin of intensity alternation.
Picosecond Luminescence Spectroscopy of Electron-Hole Plasma in GaAs/AlAs Quantum Well Structure
Authors: Tanaka S. , Kuno M. , Yamamoto A. , Watanabe A. , Kobayashi H. , Mizuta M. , Kukimoto H. , Saito H.
Published: February 2023

We report the picosecond temporal character of high-density electron-hole plasma (EHP), such as carrier trapping and radiative recombination process, in highly excited GaAs/AlAs multiple quantum well (MQW) structures.
Subnanosecond Carriers Lifetime Measurement in 1.3μ InGaAsP
Authors: Sermage B. , Benchimol J.L. , Heritage J.P.
Published: February 2023

Luminescence decay time has been measured in pure InGaAsP layers (Nd-Na- 1016 cm−3) whose composition corresponds to a band gap of 1.3μ(1). The sample was excited by a 1.06μ mode locked yag laser giving 100ps long pulses separated by 10ns. An accoustooptic cristal select one impulsion every 200ns to avoid heating of the sample and allow measurement of long decays. The carrier density is calculated by the knowledge of the excitation spot size and of the absorbed power. We make sure that the layer is situated at the beam waist by taking profit of the saturation of the absorption. The carriers density is varied between 4.1016 and 2.1019 cm−3 by changing the excitation intensity. The radiative recombination life time τr has been calculated with the Fermi golden rule, using the Kane model for the description of the lower conduction band and the three upper valence bands near the center of the Brillouin zone. The value of the matrix element is obtained by taking into account the measured absorption coefficient (α = 1.6 104 cm−1) at 1.06μ. The carriers life time τ is deduced from the luminescence decay time τL by taking into account the theoretical variation of the luminescence intensity as a function of the carriers density.
Reabsorption Kinetics of Free- and. Bound-Exciton Luminescence in High-Purity n-GaAs
Authors: Aoki K. , Yamamoto K.
Published: February 2023

We have investigated the reabsorption kinetics of free- and bound-exciton luminescence near the surface in high-purity n-GaAs (n=2×1014/cm3) at 4.2 K, with using a sensitive detection technique which measures precisely the reabsorption quantities of the crystal-bulk luminescence excited by the dual laser beams. As well as the large reabsorption effects of the donor bound exciton (D°,X), we have found for the first time the reabsorption anomaly of the exciton-polariton luminescence just above the bottleneck region.
Evidence for a Double Acceptor Bound Exciton in a II-VI Compound
Authors: Dean P.J. , Kane M. , Skolnick M. , De Maigret F. , Dang Le Si , Nahmani A. , Romestain R. , Magnea N.
Published: February 2023

Annealing of II-VI compounds like ZnSe in contact with molten Zn is known to convert them to n-type. In ZnTe this procedure although increasing the donor concentration has the major effect of introducing a hole level 170-190 meV above the valence band and keeps it p-type. It also introduces an intense emission line labelled

A
1
×

at 2.361 eV. We will show that this line is due to the recombination of an exciton bound to a double acceptor with the same first ionization energy.
Femtosecond Measurement of Configurational Relaxation with the Soliton Laser
Authors: Mollenauer L. F.
Published: February 2023

There are many questions surrounding the configurational relaxation that follows optical excitation of luminescent systems. Fundamental to the resolution of these questions is a measurement of the configurational relaxation time. For systems involving an intimate coupling with phonons, such as organic dyes or color centers, relaxation times are expected to be on the picosecond or subpicosecond time scales, even at zero temperature. Thus, resolution to a very small fraction of a picosecond is required, if the (highly temperature-dependent) relaxation of such systems is to be measured over a significantly wide temperature range. Fortunately, recent developments1,2 in ultrashort pulse lasers have opened up the possibility of such measurement. This talk concerns one such source, the "soliton laser"2, and its use on systems with near-infrared absorption bands.
Steady-state and time-dependent luminescence of UO2MoO4
Authors: Smit W.M.A.
Published: February 2023

The crystal structure of UO2MoO4 is monoclinic with four molecules in the unit cell. The space-group is

P

2
1

/

c-C

2
h

5

[1] and the uranium ions occupy sites with C1 symmetry revealing that the uranyl groups have lost their D∞h symmetry.
Effect of Ba+2 Cation Impurity Concentration on the Thermally Stimulated Luminescence of Sodium Chloride.
Authors: Mahajan O. H. , Joshi T. R. , Kathuria S. P. , Joshi R. V.
Published: February 2023

Summary not available
Role of Dislocations in the Mechanoluminescence Excitation of Irradiated and Non-Irradiated Alkali Halide Crystals
Authors: Chandra B. P.
Published: February 2023

Mechanoluminescence (ML) or triboluminescence is a type of luminescence produced during mechanical deformation of solids. The present peper reports the role of dislocations in the ML excitation of irradiated and non-irradiated alkali halide crystals.
Pulsed luminescence from non-equilibrium distribution of FA(II) centers in KCl:Li+.
Authors: Baldacchini G. , Grassano U.M. , Meucci M. , Scacco A. , Somma F. , Tonelli M.
Published: February 2023

After their first appearance and the following developments in the connected technology during the last few years, color center lasers proved to be a powerful tool for a widespread range of applications, such as high resolution molecular spectroscopy, laser chemistry, pollution detection and studies of propagation in optical fibers. Although several types of color centers in different alkali halide crystals have been investigated in order to obtain laser action, the FA(II) center still appears the most suitable for operation in the 2-3 μm range.
Two-Photon Excitation of the Luminescence in Bismuth Germanate
Authors: Casalboni M. , Francini R. , Grassano U.M. , Musilli C. , Pizzoferrato R.
Published: February 2023

Excitation of bismuth germanate (Bi4Ge3O12) single crystals with ultraviolet or X-ray photons of wavelength shorter than 300 nm produces a broad emission band centered around 500 nm.
Laser Induced Multisite Emission of Pr3+ in CaF2 at Low and Room Temperatures
Authors: Chrysochoos John
Published: February 2023

Direct excitation of the 3PO-state of Pr3+ in CaF2 using 4765 Å (Ar-ion laser) at low temperatures leads to emission attributed to at least three distinct Pr3+-sites (1,2). The present paper deals with multisite emission of Pr3+ in CaF2 under excitation conditions leading to indirect population of the 3PO-state.
Luminescence and Defects in Ca2+ Doped Thoria Crystals
Authors: Kristianpoller N. , Rehavi A.
Published: February 2023

The luminescence emitted during X-irradiated (XL) as well as the thermoluminescence (TL) of single ThO2:Ca crystals were studied. Results were compared to those obtained for pure Thoria crystals.[1] The TL was excited at 80 K by X or monochromatic vacuum-ultraviolet (vuv) radiation and excitation spectra were measured between 130 and 250 nm. Measured were also the spectral composition of the emission and the temperature dependence of the main XL emission bands. Results show that after uv irradiation TL peaks appeared at the same temperatures and with the same activation energies as after X-irradiation and after self excitation of the radioactive material, indicating that they are due to the same defects. The absorption edge of ThO2 is at about 213 nm. The excitation spectrum of ThO2:Ca showed maxima at 146, 163, 170 and 183 nm. Essentially the same maxima were recorded for pure ThO2.
Fluorescence of Molecules on Metal Island Films
Authors: Harris Timothy D.
Published: February 2023

The same substrates used to produce surface enhanced Raman scattering can also induce large changes in the fluorescence of nearby molecules. Unlike Raman scattering the rate of emission and the intensity are considered separately. The increase in emission rate has been shown to exceed 103 on silver island films (1,2) with a simultaneous enhancement of intensity. Such a large change in emission rate with no loss of intensity provides an avenue for exploitation in emission spectroscopy.
Quantum statistical theory of Laser/surface-catalyzed migration
Authors: Lin Jui-teng
Published: February 2023

The possibility of laser-controlled heterogeneous catalysis is theoretically investigated in terms of the laser/phonon-enhanced migration of species adsorbed on a catalytic surface. The migration rate, influenced by both the thermal phonon energy and the coherent laser excitation, is studied by a quantum statistical theory.
Fluorescence Depolarization of Fluorescein in Living Lymphocytes
Authors: Kinoshita Shuichi , Fukami Tatsuya , Saito Akiya , Hirata Kuniko , Kushida Takashi , Kinoshita Yoshihiro , Kimura Shuhei
Published: February 2023

The degree of polarization of fluorescence from fluorescein, introduced into living lymphocytes, changes according to physiological conditions of the cells and also with antigenic stimulations on lymphocytes. This property can be used for a sensitive detection of malignant diseases. However, the physical mechanism of this fluorescence depolarization is not yet known.
Food Oxidation as Measured by Chemiluminescence
Authors: Löliger Jürg , Saucy Françoise
Published: February 2023

The deterioration of dietary lipids by oxidation reactions is an important topic of food science and nutrition. A large number of scientific approaches have been chosen to deal with this problem. The analytical assessment of the state of oxidation of foods is an important aspect for better understanding lipid autoxidation.
Luminescence of Tetravalent Uranium in the Incommensurate Phase of ThBr4 and ThCl4
Authors: Genet M. , Delamoye P. , Krupa J.C. , Malek C. Khan
Published: February 2023

The incommensurate phase of ThBr4 [1] and ThCl4 have been found recently. The complete study of the crystal structure by neutron diffraction leads to the following results : - ThBr4 shows a phase transition at 95 K and, down to 4 K, the observed phase is incommensurate all over this temperature range (without any lock-in). A similar behaviour is exhibited by ThCl4 with a temperature transition at 70 K.
Spectral Band Assignments for Cu+ and Ag+ in Alkali Halides via Two-Photon Spectroscopy
Authors: McClure Donal S.
Published: February 2023

See WD25 for summary.
Characterization of Optical Techniques of Particles Emitted from Surfaces
Authors: Tolk N. H.
Published: February 2023

I will discuss recent measurements of (a) laser-induced fluroescence of neutral atoms electronically desorbed from surfaces, and (b) coherence in excited states of hydrogen formed near surfaces.
Total Internal Reflection Fluorescence in Biological Systems
Authors: Axelrod Daniel
Published: February 2023

Fluorescence of labeled proteins near a solid/liquid interface can be excited by the evanescent field of total internal reflection to study reversible adsorption kinetics and surface diffusion.
Statistical Distribution of Phonons Emitted in Multiphonon Transitions
Authors: Huang Kun
Published: February 2023

The multiphonon transition theory as formulated by Kubo and Toyozawa provides a general framework for dealing with arbitrary phonon spectra. However, in dealing with concrete problems, single frequency models are widely used. To overcome the inadequacy of over-simplified models and to make theoretical calculations practically feasible, the concept of multi-frequency models is developed. The theoretical basis for the use of the method of steepest descent with multi-frequency models is discussed. It is shown that the use of the contribution of the principal saddle point alone just serves to smooth out artificial singular structures introduced by the model.
Identification of Deep Radiative Levels in VPE ZnSe
Authors: Christianson K. A. , Wessels B. W.
Published: February 2023

The defect centers responsible for the deep level emission commonly seen in the photoluminescence (PL) spectra of high purity VPE ZnSe have been studied. The ZnSe layers examined were heteroepitaxially deposited on GaAs by chemical vapor deposition, with palladium diffused hydrogen as the carrier gas. Under low excitation conditions, the 1.94, 2.2 and 2.7 eV emissions are usually observed at 77 K. A large dependence of the relative magnitudes of the observed PL bands upon crystal growth conditions was noted. For example, the free to bound emission at 2.7 eV was found to peak in intensity at a substrate growth temperature of 730 °C. For those samples whose free to bound emission at 2.7 eV predominates, hole traps at Ev+0.09 and Ev+0.13 eV have been observed by optical deep level transient spectroscopy (ODLTS). For these centers, concentrations as high as 2x1015 cm−3 have been measured. The origin of the two deeper emissions is not as clear, since the defect center responsible has not been detected by ODLTS. However, a potentially responsible defect level (at Ev+ 0.5 eV) has been observed by steady state photocapacitance at 77 K.
On the Nature of the CdS: In,Cd Film Edge Emission Bands
Authors: Vlasenko N.A. , Denisova Z.L.
Published: February 2023

Edge emission is known to be observed in donor-doped CdS /1–3/. The question that remains is the nature of its individual bands, especially in emission spectra of films. In this paper the edge photoluminescence (PL) and electroluminescence (EL) of vacuum-deposited low-resistivity (10–10−1 Ohm cm) CdS:In, Cd films have been studied over the range 4.2 to 300 K. The films, 1-3μ thick, were deposited onto glass, mica or molibdenum substrates by the methods described in /3/. The MISM structures of Au-In2O3-CdS-In2O3(Mo) were used in EL experiments.
Sensitized Luminiscence and Energy Transfer in CaF2-Ho3+, Eu2+ System
Authors: Kiriluk L.V.
Published: February 2023

The Spectra of luminiecence and the absorption of concentration series of monocrystals CaF2-Ho3+ and CaF2-Ho3+, Eu2+ synthesized in a fluorined medium under 300 and 77°K (Stockbarger method) have been investigated on the difraction spectrometer with the riverse linear dispersion of 5 Å/mm and monocrystals CaF2-Eu2+ have been investigated on the spectrophotometer (SF-4A).
Terbium Activated Rare Earth Oxyorthosilicates
Authors: Leskelä Markku , Suikkanen Juha
Published: February 2023

Two different monoclinic structures have been found in rare earth oxyorthosilicates: the first (La…Tb) has the space group P21/c and contains 9 and 7 coordinated cations, the second (Dy…Lu) has the space group B2/c and also has two different cation sites with coordination numbers 6 and 7 (1). The literature concerning La2(SiO4)O is contradictory and it seems that lanthanum does not belong to the first structure group but has an unknown structure of its own (2). The literature of rare earth silicate phosphors is limited and is mostly patented.
Laser Induced Defect Centers in Ce3+:CaF2
Authors: Pogatshnik G. J. , Gayen S. K. , Hamilton D. S.
Published: February 2023

Upon irradiation of a 1.3 mm thick sample of 0.05% Ce3+:CaF2 with the 308 nm emission of a XeCl excimer laser, we have observed coloration of the crystal by laser induced defect centers. The absorption spectrum of the induced centers is broad band and peaks at about 500 nm. The defect center has been associated with the excitation of cerium ions in the crystal. By irradiating with a 351 nm laser of comparable intensity, no colo­ration was produced. The centers are only created if one pumps into the 4f to 5d absorption band of the cerium ions in near resonance with 308 nm.
The Effect of the J-mixing on the Intensities of the f-f Transitions of Rare-earth Ions
Authors: Shang-ta Hsia , Yi-min Chen
Published: February 2023

Taking the effect of the J-mixing into account in the consideration of luminescense of rare-earth ions on low symmetry positions in solids, we derive the following line strength formula for electric-diople transition from term ψ
i
J
i
to term ψ
f
J
f
(modified Judd’s three parameter band intensity formula1) where ψJ is the same thing as τ2
S
+1
LJ
, the term label; |a(ψJ,ψ′J′)|2/(2J′+1) is defined as the j-mixing coefficient between term ψJ and term ψ′J′.
Electronic Structure and Energy Levels of the Phosphor ZnS:Tm3+ Using Nonrelativistic and Relativistic Cluster Calculations
Authors: Guo Changxin , Ellis D.E.
Published: February 2023

Luminescence properties of rare earth doped ZnS were extensively studied recently. The main purpose of these works was to optimize the synthesis methods for phosphors, to study the properties of luminous centers and energy transfer from ZnS→Ln3+, and by using the rare earth ion as a local structural probe, to study the crystal field properties of the environment. The studies of trivalent thulium Tm3+ doped in crystalline ZnS was reported by several authors[1,2,3]. The experimental results of emission properties and crystal field parameters of ZnS:Tm3+ were mentioned.
On Spectral Energy Distribution Shape of Fluorescent Lamp Phosphors
Authors: Narita K.
Published: February 2023

Fluorescent lamp phosphors activated by complex ions(WO42- etc.), s2 configuration ions, Mn2+ or Eu2+ show broad band emissions. The spectral energy distribution(SED) shape for some selected phosphors has been discussed(1,2). We report a more generalized observation on these phosphors to deduce the SED features inherent in each of the activators. Every observed SED was plotted in terms of

−
log

(

I/I

0

)

vs. wavenumber to compare it with the Gauss error function(I:Energy,I0:Maximum energy of SED).
Scintillating Glass Fiber-Optic Plates For The Detection of Ionizing Particles
Authors: Ruchti R. , Baumbaugh B. , Bishop J. , Biswas N. , Cason N. , Erichsen R. , Kenney V. , Mountain R. , Shepard W. , Kreymer A. , Rogers A. , Meade R.
Published: February 2023

We have developed and studied the performance of scintillating glass fiber-optic plates composed of: (1) Terbium activated cladded-glass cores in a matrix of 15 um spacing; and (2) Cerium activated cladded-glass cores in various matrices of 6-25 um spacing. The fluorescence properties of the base glasses and the fiber-optic plates have been studied extensively using Xe lamp and pulser laser spectrometers. The response of the fiber-optic devices to high energy charged particles was measured using 10 GeV/c particles at the SLAC test beam facility and 100 GeV/c particles at Fermi lab. The plates were viewed with a three-stage, gateable image intensifier. Particle tracks and nuclear inter actions were recorded on film. We observe 5 detected flourescence photons per millimeter for minimum ionizing particles for the Terbium glass and 3 detected photons per millimeter for the Cerium glass. The test results indicate that the scintillating glass fiber-optic plates can be used as high resolution tracking detectors for both fixed target and colliding-beam experiments in high energy and nuclear physics.
Nonlinearity of the cathodoluminescence intensity of ZnS-type phosphors.
Authors: de Leeuw D.M.
Published: February 2023

The cathodoluminescence of ZnS-type phosphors shows a sublinear increase with increasing excitation density. The widespread use of these phosphors in cathode-ray (CR) tubes has led to many investigations on this so-called saturation behaviour (1,2). However, these studies have not resulted in a satisfactory understanding of the observed saturation phenomena for two reasons.
"1.5μm to 0.65 m Up-Conversion by "Summation of Photons by Energy Transfer" Effect in Diode Pumped Vitroceramics".
Authors: de Sá G.F. , Santa Cruz P.A. , Auzel F.
Published: February 2023

APTE effect (Addition de Photons par Transferts d'Energie) in (Yb3+, Er3+) doped vitroceramics has been found to be a very efficient process to obtain up-conversion by summation of photons [1] [2] [3] [4].