bluuebunny/crossref_metadata_2025 huggingface dataset:
Rotation of Elliptical Polarization in High Harmonic Generation
Authors: Bucksbaum P. H. , Weihe F. , Dutta S. , Korn G. , Du D.
Published: February 2023

The efficiency for generating ultra-high harmonics (HHG) in intense laser fields has been studied as a function of many parameters, such as the density or composition of the nonlinear medium; the wavelength and intensity of the light; and the incident polarization.1-3 The characteristic "plateau," or slow variation in efficiency over many high harmonics, is now known to depend on these parameters in a manner consistent with the predictions of some recent theories, in which harmonics are due to inelastic rescattering of field-ionized electrons driven against their parent ion by the laser field.4-6
Efficient Generation of a Collisional X-ray Laser with a Small Beam Divergence
Authors: Kodama R. , Kato Y. , Daido H. , Murai K. , Yuan G. , Ninomiya S. , Neely D. , Macphee A. , Nam C. H. , Choi I. W.
Published: February 2023

For the improvement of collisional x-ray laser propagation in laser produced plasmas, we have experimentally investigated the plasma waveguiding of the x-ray laser beam propagation by using a curved slab target. Double-short pulse pumping was also examined to improve the generation efficiency of the collisional x-ray lasers.
X-Ray Spectroscopic Investigation of Optical-Field Ionized Plasmas
Authors: Borgström S. , Fill E. , Larsson J. , Starczewski T. , Svanberg S. , Wahlström C.-G.
Published: February 2023

Soft X-ray spectra of N, O, C, S, He and Ar ions generated by optical-field ionization with fs pulses are reported. The experiments were carried out by focusing pulses of the high-power Ti:Sapphire laser of the Lund Institute of Technology (wavelength 800 nm, pulse duration 150 fs, pulse energy 150 mJ) to a 60 µm diameter spot below a pulsed gas nozzle or within a windowless pulsed gas cell, using N2, O2, CO2, SF6, He and Ar as parent gases.
Observation of Stabilization against Photoionization due to the Formation of a Rydberg Anti wavepacket
Authors: Hoogenraad J. H. , Vrijen R. B. , Noordam L. D.
Published: February 2023

We have observed that the amount of photoionization from an atomic Rydberg state with a pulsed laser depends critically on the length of the pulse, whereas lowest order perturbation theory implies that the yield only depends on the fluence (the integrated intensity) of the pulse. We have measured the yield for one-photon ionization with short (0.3 to 2.7 ps), high-intensity laser pulses from the 27d Rydberg state in barium. With equal fluence, the yield decreases for pulses shorter than the Kepler orbit time of the outer electron (2.2 ps), as not all of its wavefunction comes near the core during the length of the pulse. The observations and this classical picture are confirmed by quantum mechanical calculations.
Femtosecond X-rays by Orthogonal Thomson Scattering
Authors: Chattopadhyay S. , Chin A. , Glover E. , Kim K.-J. , Leemans W. , Schoenlein R. , Shank C. V.
Published: February 2023

Scattering of femtosecond optical and near infrared pulses off a low energy relativistic electron beam at 90° offers an interesting possibility to generate ultrashort pulses of x-rays. The x-ray pulses are short since the electron beam can be squeezed and focussed hard transversely, thus matching the interaction time with the femtosecond optical pulse duration. This is difficult with collinear scattering since electron beams with lengths less than a few picoseconds are hard to produce. The method has some intrinsic attractive features, e.g. simplicity of concept, directivity, tunability, etc. Experiments are under preparation in the Beam Test Facility of the Center for Beam Physics at LBL where a 30 MeV electron beam from the ALS injector linac will be scattered against a 0.8 μm, 100 mJ/pulse Terawatt femtosecond laser. Short pulse x-ray detection schemes are under development as well.
Impact ionization in dielectrics with pulse widths ranging from 150 fs to 7 ns
Authors: Du D. , Liu X. , Korn G. , Squier J. , Mourou G.
Published: February 2023

Impact ionization is one of the processes of electron transport under extremely high fields. Previous measurements are limited by the dielectric breakdown up to 107 V/cm with a static electric field. With ultrashort lasers, however, we are able to measure the ionization coefficient up to 2.8 × 108 V/cm for the first time. We utilized the optical breakdown of normally transparent optical materials, such as fused silica, to study this ionization phenomona. Through the nonlinear photon-matter interaction (electron avalanche process or multiphoton ionization), a plasma is generated at the focal spot and laser energy is deposited in the material.
Selectivity, Sensitivity, Speed, and Sub-Doppler Resolution Are Not Incompatible
Authors: McCarthy Michael C. , Kanamori Hideto , Li Mingguang , Field Robert W.
Published: February 2023

The combination of magnetic rotation electro-optic frequency modulation, and sub-Doppler δmj = 2 Zeeman resonance tunable laser techniques yields J, δj, and gJ presorted spectra at near shot-noise-limited sensitivity.
Time-resolved optical double resonance spectroscopy in acetylene : exploring rovibrational energy transfer at various levels of excitation
Authors: Milce A. P. , Barth H.-D. , Chadwick B. L. , Orr B. J.
Published: February 2023

Time-resolved optical double resonance (DR) techniques are useful not only for high-resolution spectroscopy, but also for studies of the mechanisms by which molecules transfer energy from one distinct rovibrational quantum state to another, thereby elucidating aspects of chemical reactivity and energetics. The DR approach employs tunable laser excitation to prepare a molecule in a specific state and a second laser absorption step either to characterise that excitation or to probe resulting state-to-state molecular energy transfer. Typically, we use either infrared (IR) absorption or coherent Raman excitation for state preparation and ultraviolet (UV) laser-induced fluorescence (LIF) for detection. The emphasis in this work is on high state-specificity and sensitivity, to enable detailed modeling of the resulting spectroscopic and kinetic data and to provide insight into the intermolecular and intramolecular energy transfer processes involved. Figure 1 depicts the LIF-detected Raman-UVDR and IRUVDR excitation schemes.
Inverse Raman Spectroscopy Measurements of Line-Shift Coefficients in Hydrogen Perturbed by Argon
Authors: Forsman J. W. , Farrow R. L. , Rahn L. A.
Published: February 2023

High resolution Raman studies of the Q branch in H2 perturbed by Ar are relevant to combustion diagnostics and for tests of the intermolecular potential. The use of spectroscopic techniques to study combustion requires accurate models for the line shapes, which can range front Lorentzian to Gaussian to more complicated profiles1 depending on the perturber species, perturber concentration, density and temperature. Calculations with these models require estimates of the speed dependence of the line-shift and line-broadening coefficients. Modern theories are now able to predict the shifting and broadening resulting from collisions but are hampered by uncertainties in the interaction potential. One of the most studied potentials is that of H2-Ar, which has the advantage of being theoretically tractable for line shape computations. Furthermore, since the masses of Ar and molecular O2 and N2 are similar, spectral features depending on the perturber’s mass are expected to be similar. We report preliminary measurements of the density shift of the Q branch lines in H2 as a function of rotational state and temperature.
High Resolution Electronic Spectroscopy of ZnCH3 and CdCH3
Authors: Cerny Timothy M. , Tan Xue-Qing , Robles Eric S. J. , Ellis Andrew M. , Williamson James M. , Miller Terry A.
Published: February 2023

The number of organometallic free radicals studied spectroscopically in the gas phase has been very limited until quite recently. Application of Broida oven, laser photolysis and laser photolysis/vaporization techniques to synthesize these transient species has significantly enlarged the number of reports over the past few years. This research group’s contribution to the area have been a series of reports by Robles, Ellis and Miller detailing electronic and vibrational structures (~.5 cm-1 resolution) of 15 species of the form M-R (M = Mg, Ca, Zn and Cd; R = cyclopentadienyl (Cp), pyrollyl (Py) and methylcyclopentadienyl (MCp)) and M-CH3 (M = Ca, Zn and Cd), many of them observed for the first time.1-8 These molecules are more than simply novel constructs. The methyl and Cp derivatives are recognized as important intermediates in metal deposition processes while the metal-Py species are found as subunits in several chemical substances of biological importance. Metal-ligand bonding sites, vibrational frequencies, spin-orbit splittings and barriers to internal rotation are some of the types of information that this work has yielded. To augment this work, a rotationally resolved study is presented here which confirms the electronic state symmetry assignments given in earlier studies, and more importantly, determines rotational constants and other interaction parameters of these radicals.
Tunable Far-Infrared Laser Spectroscopy of Hydrogen Bonds
Authors: Stockman Paul , Suzuki Sakae , Blake Geoffrey A.
Published: February 2023

Sub-Doppler far-infrared vibration-rotation-tunneling spectra of several water- and ammonia-containing clusters will be presented. Intermolecular potential energy surfaces derived from these spectra will also be discussed.
Electronic Surface State and Plasmon-Phonon Coupled Excitations at the surface of Modulation-doped GaAs/AlGaAs Multiquantum Wells: A Study of High-Resolution Electron-Energy-Loss Spectroscopy(HREELS)
Authors: Yu R. H.
Published: February 2023

A selfconsistent framework for study of the surface electronic structure of finite superlattices has been proposed. Our emphasis is on the influence of accumulation or depletion layer on the surface states (Tamm states). We have used a modulated doping profile, including an accumulation or a depletion surface layer, in our selfconsistent calculations of potential and carrier density profile. We have found the existence of Tamm states above(depletion layer) or below(accumulation layer) the superlattice miniband. One of the Tamm states found crosses the Fermi energy in the energy gap when the depletion effect, resulting from dangling bonds, defects, impurities, etc, near the surface increases. In our case, near the top layer of the superlattice the depletion region was formed as a result of the pinning of the Fermi level below its position in intrinsic GaAs due to the midgap surface states.
Color change and highly refractory surfaces of polycrystalline silicon of arsenic atoms of high dose implanted at low acceleration voltage, as the interesting object of the Raman spectroscopy
Authors: Saito Yasuyuki
Published: February 2023

Polycrystalline silicon surface of arsenic atoms of ≃1015 cm−2 implanted at 40keV showed color change from gold to light–red under a fluorescent light and highly refractory obstacle against exposure etching of radical fluorine excited with microwave. The refractory surface mechanism may be related to the fastening of vibration of lattice Si atoms of polycrystalline silicon. This is an interesting object for analysis of the Raman spectroscopy.
Spectroscopic Studies of Weakly Bound Molecular Complexes
Authors: Klemperer William
Published: February 2023

We present recent results of the studies on the following systems. Arl2 (With M.L. Burke), ArHCN(with S. Drucker and A.L. Cooksy) and ArHF and (HF)2 (with H. Chang).
Infrared-Molecular Beam Spectroscopy: the Study of Weakly Bound Molecular Complexes as a Probe of Potential Energy Surfaces and Molecular Dynamics
Authors: Miller Roger E.
Published: February 2023

Infrared laser spectroscopy has become a powerful tool in the study of weakly bound molecular complexes. The molecular constants obtained from these spectra can be used to determine the "structure" of the complex, for systems where this is a meaningful concept, while, in complexes which undergo wide amplitude excursions from their equilibrium geometries, the spectroscopy is often sensitive to the details of the intermolecular potential energy surface. In many cases, these spectra are sensitive to both the internal dynamics of the complex and the vibrational predissociation dynamics that result from the excitation process.
The First Rotational Analysis of the Infrared Spectrum of Dimethylacetylene
Authors: Bunker P. R. , Johns J. W. C. , McKellar A. R. W. , Di Lauro C.
Published: February 2023

The perpendicular fundamental bands of dimethylacetylene have long been of interest to spectroscopists. This is because it is in these bands that two interesting effects manifest themselves. The first of these effects is the splitting of certain rotational lines caused by the small barrier to internal rotation. And the second effect is the shift of intensity within the band due to the coupling (through the acetylene bond) of the perpendicular methyl vibrations from one end of the molecule to the other.
Low Pressure Measurements of Line Broadening Coefficients in CH3F
Authors: Nischan M. , Clark D. , Guerin D. , Mantz A. W.
Published: February 2023

Interpretation of low pressure measurements of pressure broadened line widths is made difficult by the fact that Doppler line width and measurement laser line width both generally contribute significantly to the total line width. This is further complicated by the fact that the Doppler and Laser contributions are non linear in the low pressure regime when the line width is plotted as a linear function of pressure.
Multi-Channel Flash X-Ray Tomography of Transient Events
Authors: Zoltani C.K. , White K.J.
Published: February 2023

Spurred by a need for density cross-sectional profiles of objects in rapid motion, a nondestructive testing diagnostic facility for microsecond events is under development at the Ballistic Research Laboratory. Previous interest in tomography of transient events centered on the study of cyclic processes, such as the human heart, with the DSR and the Imatron achieving remarkable successes. The present development addresses the problem where data must be gathered in a few microseconds to preclude blurring and other unwanted side effects. This is achieved by simultaneous recording of all the data, without any mechanical motion of the sources and detectors.
Tutorial on Iterative and Object-Dependent Algorithms
Authors: Rangayyan Rangaraj M.
Published: February 2023

Summary not available.
Exciton Hola Burning in GaAs/GaAlAs Multiquantum Wells
Authors: Hegarty J. , Sturge M. D.
Published: February 2023

See FE17 for summary.
Luminescence properties of ultra-pure pyridine
Authors: Ghoshal S. K. , Maiti A. K. , Kastha G. S.
Published: February 2023

We report here for the first time the observation of both fluorescence and phosphorescence emissions from extensively purified samples of pyridine. An ultra-pure sample of pyridine was obtained through the following purification steps. E. Merck spectrograde pyridine was first treated with hydrochloric acid (GR arade) and the pyridine hydrochloride thus formed was subjected to repeated fractional distillation. The final middle fraction pyridine hydrochloride was then treated with sodium hydroxide. The pyridine liberated was fractionally distilled several times, dried over anhydrous sodium hydroxide, and finally fractionated before use. Pyridine when freed of impurities (viz., pyrazine) has been found to exhibit weak but readily observable fluorescence as well as phosphorescence emissions, both of π, π * character, in its pure crystalline state and in a variety of glassy and crystalline matrices (e.g., benzene, cyclohexane, methylcyclohexane, ethanol and water) at 77 K. Phosphorescence of pyridine is characterized by a long phosphorescence lifetime (τ~ 2s) and a broad and structureless spectrum with λmax~ 420 nm. The fluorescence spectrum (λmax~ 290 nm) shows some vibrational structure in crystalline media. In addition to these S2 ( π, π*) → S0 and T1 ( π, π*) → S0 emissions, a very weak emission attributable to S1 ( n, π
*
) → S0 fluorescence (stretching a spectral region 310 — 350 nm) has also been observed in the emission spectrum of pyridine in rigid matrices. No fluorescence emission could be dected either in the vapor or in solution phase at room temperature.
Usefulness of Sensitized Luminescence as a Probe for Exciton Motion in Molecular Crystals: Proposal for New Experiments for the Investigation of Transport Coherence of Excitons in Molecular Crystals
Authors: Kenkre V.M. , Parris P. E. , Kenkre V.M. , Tsironis C.P.
Published: February 2023

See FD13 and1 FDl4 for summaries.
Vacancy-Vacancy Interaction in the Excitation Spectra of Lattice Perturbation Bands in Cu2O
Authors: Kaufman R. G. , Hawkins R. T.
Published: February 2023

We have recently found techniques for easily changing the density of copper vacancies in 30 μm films of Cu2O on copper. A high density of copper vacancies is produced at 1000°C in a thin layer near the surface of the Cu2O film, subsequent heat treatment in argon at lower temperatures lowers the vacancy density by diffusion throughout the film. Water quenching quickly stops diffusion and prevents further oxidation. New excitation spectra using a double monochromator have been measured at twenty five degree intervals between room and liquid nitrogen temperature for oxygen vacancy emissions at 740 nm, 840 nm, and the copper vacancy emission at 940 nm for heat treatment temperatures of 300°C, 400°C, 500°C, 600°C, and 700°C.
Radiative Recombination of Bound Excitons with Site Transfer Final State Excitations in Cu-Doped ZnTe
Authors: Monemar B. , Holtz P.O. , Gislason H.P. , Magnea N. , Uihlein Ch. , Liu P.L.
Published: February 2023

Novel recombination lines are observed as electronic satellites to bound excitons (BE:s) in photoluminescence (PL) spectra of Cu-doped ZnTe, when the doping is sufficiently-strong (1017-1018 cm−3) that complex Cu-related defects dominate the BE spectra. These replica are observed at discrete energies in the range 90-170 meV below the PL lines caused by the direct recombination of the BE state. The strength of these satellites is typically 5-10% of the parent BE line, and has a similar width (~0,2 - 0,4 meV). Such satellites occur with BE recombination for acceptor BE:s (ABEis) as well as isoelectronic complex BE:s (IBE:s). They also occur in a similar way in resonant Raman scattering (RRS). Magnetooptical data at 10T reveal an extremely complicated Zeeman splitting pattern of these satellites. The collected experimental data from selective dyelaser excited luminescence (SPL) spectra and excitation spectra (PLE) together with RRS and Zeeman results, suggest a recombination model where the BE state is interacting with a neutral acceptor state on a different site,, In the recombination process final state electronic shake up excitations of the type 1s-2s are observed on acceptors which are interacting with the defect site carrying the initial state BE excitation.
Triplet Excimers in Hexachlorobenzene Crystals
Authors: Wolf H. C.
Published: February 2023

From ENDOR measurements on tiplet excimers in single crystals of hexachlorobenzene doped with trichlorobenzene, one can derive for the first time the detailed electronic and geometric structure of an excimer.
Laser Spectroscopy of Atoms, Molecules, and Solids
Authors: Schawlow Arthur L.
Published: February 2023

The powerful, directional and monochromatic light of tunable lasers makes it possible to resolve fine details in spectra and to distinguish spectroscopic centers within inhomogeneously broadened lines. Some particular examples of spectroscopic studies employing these laser techniques will be discussed.
Luminescence Studies of Restricted Molecular Motion in Liquids
Authors: Hochstrasser R. M.
Published: February 2023

Summary not available.
Luminescence of Cs2ZrCl6 and Cs2HfCl6
Authors: Bryan Philip S. , Ferranti Steven A.
Published: February 2023

The hexachlorometallates Cs2ZrCl6 and Cs2HfCl6, formed by the treatment of CsCl in concentrated HCl with either zirconium or hafnium oxychloride, fluoresce efficiently when excited by x-rays or radiation at 254 nm. The excitation and emission spectra obtained from powder samples of the two compounds are nearly identical. For the Zr complex, the maxima for excitation (narrow band) and the emission (broad band) are at 258 and 451 nm, respectively. The corresponding values for the Hf complex are at 254 and 449 nm. The quantum yields with excitation at 254 nm are near unity. The t1/2 value for the fluorescence decay is about 10 μsec for both compounds when excited with a 40 nsec pulse from a filtered 110 kVp x-ray source.
Thermoluminescence Kinetics in Systems More General than those Described by the Usual 1st and 2nd Order Kinetics*
Authors: Levy Paul W.
Published: February 2023

In an effort to explain anomalous thermoluminescence (TL) measurements, that cannot be described by the well-known 1st and 2nd order kinetics, more general TL kinetics have been developed. The anomalous results include glow peak shapes that cannot be described by the usual kinetics, the appearance of physically unrealistic parameters that are unusual functions of the premeasurement dose, etc. As is well known, the usual 1st order TL kinetics is obtained from an expression, called here the general one-trap kinetic equation, by assuming that thermally released trapped charges undergo light emitting recombination without being retrapped. The usual 2nd order kinetics is obtained, from the same equation, by assuming that retrapping occurs and, first, that the retrapping and recombination cross sections are equal, and, second, the trapped electron and hole concentrations are equal. The general one-trap kinetic equation has been investigated by numerically computing glow curves using physically reasonable parameters. In turn, these curves are regarded as "data" and analyzed by fitting them to the usual 1st and 2nd order expressions. A number of anomalous results are reproduced. The computed glow peaks depend strongly on the dose, the retrapping-recombination cross section ratio, etc. They are approximated, but not in the wings, by the usual 1st and 2nd order kinetics. However the kinetic parameters obtained usually differ appreciably from those used to compute the glow peaks.
[Title not available]
Authors: Joubert M.F. , Linarès C. , Jacquier B. , Wanklyn B.
Published: February 2023

We report the results of an investigation of optical spectroscopy of two terbium concentrated materials : TbF3 and TbAlO3 at very low temperature. From magnetic measurements and neutron diffraction data, it is known that isomorphous TbF3 and TbAlO3 orders ferromagnetically below Tc=3.95 K and antiferromagnetically below T = 3.8 K respectively.
Kinetics of Relaxation Processes in X-Irradiated Alkali Halide Crystals by the Isothermal Monochromatic Luminescence Decay Method.
Authors: Manam Jairam , Ratnam V.V.
Published: February 2023

The isothermal luminescence decay method, one of the two basic types of relaxation methods, can be used to study the electron hole reaction kinetics in solids. The kinetic theories developed, pertaining to the electron - hole recombination reactions based on the theories of simple mono-and bi-molecular reactions and statistical thermodynamic theory of absolute reaction rates could not satisfactorily fit in nor explain the experimentally observed decays. The lack of correlation between theory and experiment is to be traced back to the need of an ‘apriori’ assumption of the order of kinetics parameter. Even the second type of relaxation, namely the non-isothermal relaxation in the form of thermally stimulated luminescence and thermally stimulated conductivity, can at best give estimates of the thermal activation energies or the trap depths, only when the order of kinetics parameter is obtained from other measurements.
Two-Color Superflorescence of O2 Centers in KCl
Authors: Florian R. , Schwan L. O. , Schmid D.
Published: February 2023

See MB38 for summary.
Inverse Photoemission in the Ultraviolet
Authors: Himpsel F. J. , Fauster Th. , Straub D.
Published: February 2023

Inverse photoemission (or bremsstrahlung spectroscopy) is the time-reversed photoemission process. Electronic states are probed via radiative transitions of an incoming electron into unoccupied states. X-ray bremsstrahlung spectroscopy is a well-established technique but its extension to the ultraviolet (with electrons incident at about 4-30 eV energy) has only begun recently. With lower electron energies the surface sensitivity increases such that monolayers can be probed. Also, the momentum of electrons in a solid can be determined by angle-resolved inverse photoemission, i.e., energy band dispersions can be mapped. Unoccupied electronic states play an important role, e.g., in ferromagnetism (minority spin states), in chemisorption (electron acceptor states of adsorbates), and for semiconductors (conduction by electrons). A status report is given and illustrated by examples in band mapping, the identification of adsorbate orbitals and the observation of surface states.
Fluorescence Probes for Biological Systems: Structural and Dynamical Studies of Red Cell Membranes
Authors: Eisinger Josef
Published: February 2023

Fluorescence probes which are sensitive to their environment, to the proximity of other chromophores and other structural or dynamic parameters have many applications in the investigation of biological systems on the molecular level. Their use in complex biological assemblies has been hampered by artifacts resulting from the absorption and scattering of excitation and emitted light within the sample. We have demonstrated that by measuring fluorescence intensity (I) or anisotropy (r) at a series of concentrations (h), the limiting values of these parameters at vanishing concentration (h - o) are given by the intercepts of the straight lines obtained by plotting log (I/h) or log r versus h. The slope of the line is a function of the absorption and scattering characteristics of the particles (e.g., cells) at the excitation and emission wavelengths and of the configuration of the fluorometer.
Optically Detected Stimulated Spin Echo as a Probe of Triplet Energy Migration in Mixed Molecular Crystals
Authors: Brenner Henry C. , Janes Stephen M.
Published: February 2023

See WE4 for summary.
Reabsorption Kinetics of Free- and Bound-Exciton Luminescence in High-Purity n-GaAs
Authors: Aoki K. , Yamamoto K.
Published: February 2023

See FF6 for summary.
Modern Status of Energy Transfer Problem in Solids Activated by Rare-Earth Systems
Authors: Gapontsev V.P. , Platonov N.S.
Published: February 2023

We fulfilled systematic investigations of energy transfer(ET) processes for more than 60 donor(d)-acceptor(a) systems of RE3+ in wide line of phosphate, silicate, borate, germanate, and tellurite glass hosts, also as in crystals of pentaphosphates, tetraphosphates, double potassium molibdates, and so on, with using the arsenal of modern precise experimental methods, in particular, the selective laser excitation method, or the method of luminescence decay kinetic in the intensity range of 4-5 orders of value. New significant results were obtained which allowed us to form the clear viewpoint on the regularities and mechanisms of different ET processes, the dependences of their constants from composition and micriscopic structure of host, the activator concentrations, the temperature, the energy mis-match, and the other factors, also as on the principal changes of ET regularities when crossing from crystalline to amorphous state.
Secondary Emission Spectra and Energy Relaxation of Polaritons in Layer Polar Semiconductors
Authors: Brodin M.S. , Blonskii I.V.
Published: February 2023

Our previous studies of integral characteristics of excitonic absorption bands in a number of typical layer semiconductors led us to some conclusions on the pecularities of relaxation mechanisms responsible for excitonic absorption. In particular, the nonlinear exciton-phonon interaction, indirect phototransitions and phonon anharmonism are all important (1). They are related to the pecularities in vibrational spectrum of layer crystals: the existence of bending waves in acoustic phonon spectrum and low-energy optical phonons (LOP) with ħω= 1÷3 meV due to extrinsic inter-layer vibrations.
Energy Transfer and Trapping of Fractals
Authors: Klafter Joseph
Published: February 2023

Summary not available
Direct Electronic Energy Transfer on Fractals
Authors: Even U. , Rademann K. , Jortner J. , Manor N. , Reisfeld R.
Published: February 2023

The site distribution of a fractal structure was characterized by the interrogation of electronic energy transfer in a porous glass, resulting in the fractal dimension of đ = 1.74±0.12 for this irregular structure.
Ambipolar Carrier Drift in Silicon by an Optical Time-of-Flight Method
Authors: Laurich B. , Forchel A. , Hoai T.X.
Published: February 2023

See TuE10 for summary.
Nonlinearity of the Cathodoluminescence Intensity of ZnS-Type Phosphors: Systematic Analysis of Phosphor Degradation under Cathode-Ray Excitation
Authors: de Leeuw D. M. , Klaasen D. B. M. , Welker T.
Published: February 2023

See TuE2 and TuE3 for summaries.
Photophysical Studies of DAQ on Silica and Aluminum Oxides. A Molecular Probe of Surface Heterogeneity
Authors: Drake J. M.
Published: February 2023

The optical features of organic molecules adsorbed to the surface of oxides, such as silica and alumina, can be strongly perturbed by the chemical properties of the surface adsorption sites. The topography of the surface as it relates to the fractal dimension and its relation to the nature and distribution of surface sites is important information if we are to be able to understand the photophysics and photochemistry of surface bound molecules. The work we report here is for the molecule 1,4 di hydroxyanthraquinone (DAQ, Quinizarin). This molecule provides striking evidence of how the surface of silica gel modifies the optical features of DAQ in different ways depending on the nature of the surface adsorption site.
d - 5 f transitions of Pa4+ in ThBr4
Authors: Naik R.C. , Krupa J.C.
Published: February 2023

I.R. emission and absorption of Pa4+ in thorium tetrahalide crystals due to transitions between 2F7/2 ⇄ 2F5/2 of 5 f1 configuration have earlier been reported. In this paper, the visible and near U.V. spectra of Pa4+ in ThBr4 are discussed. From the low temperature luminescence, absorption and excitation spectra it is concluded that 6d - 5f transitions are responsible for the observed spectra. Table I summarizes the spectral data recorded on a Jobin-Yvon HR 1000 spectrometer. Oriel-7240 monochromator in conjunction with a tungsten halogen continuum source was used to record the excitation spectra. The visible and near U.V.
Inversion Layer Formation and Electroluminescence at p-GaAs/Persulfate Solution Interface
Authors: Uosaki Kohei , Kita Hideaki
Published: February 2023

When p-type semiconductor is cathodically biased very strongly, either deep depletion or inversion layer is formed. Inversion layer formation plays a significant role in the electron transfer kinetics at semiconductor/solution interface and it is of interest to probe the inversion layer formation. The measurements of surface conductance and impedance are most often used for this purpose. If the inversion layer is formed at p-type semiconductor surface and strong oxidant which can inject holes into the valence band exists, the electroluminescence (EL) should be observed. SO4.- which is generated in situ by one electron reduction of S2O8-- is known to be a very strong oxidant and is often used to study EL of n-type semiconductors. When p-GaAs (Zn doped: 1.09 x 1019 cm-3) in solutions containing 5 M NaOH and 0.15 M S2O8-- is negatively biased, first the cathodic currents due to the reduction of S2O8-- and SO4.- are observed between -0.5 V and ca. -2 V. When the potential becomes more negative than ca. -2 V, the cathodic current due to hydrogen evolution is observed. In this potential region, EL which has peak around 880 nm is observed. Since the peak energy is in good agreement with the energy gap of GaAs, this EL seems to be due to bandadge emission. Thus, when p-GaAs is biased more negative than ca. -2.0 V, the electrons are transferred from the valence band in the bulk to the conduction band in the surface by turneling and some of them are consumed for hydrogen evolution and are recombined radiatively with holes, emitting band edge EL. The lower the carrier density, the more negative the critical potential at which the current due to hydrogen evolution started to flow and the weaker the intensity of EL. These results suggest that the electron concentration in the conduction band at the surface is lower at p-GaAs of lower carrier concentration. This is reasonable since the barrier width for the turneling is wider at p-GaAs of lower carrier concentration.
Transient Characteristic of Stimulated Raman Scattering in the Wave Guide of the Glass Fiber
Authors: Deyun Jin , Guosong Huang , Shizheng Chen , Fuxi Gan
Published: February 2023

In order to restrain the Brillouin scattering and increase the gain of the stimulated Raman scattering, the picosecond pulse train from the frequency doubled and mode-locked YAG laser with the repitition of 10-20 Hz was injected to a P2O5-GeO2-SiO2 glass fiber with the length of 20 meters. In the wave length region from 0.45μm to 1.00μm, the transient stimulated Raman scattering with the conservation effectivity higher than 50 petcent has been obtained.
Phase Coherence in the 2E state of Cr3+ ions in MgO detected via ODMR
Authors: Henderson B.
Published: February 2023

The coupling between the Zeeman sublevels of an atom by a resonant microwave magnetic field also induces a phase coherence between the states. The effect is equivalent to the precession at the Zeeman frequency of a transverse magnetic moment about the static magnetic, and is manifest as a modulation of the circularly polarized emission at the Zeeman frequency. We have investigated such phase coherence in the 2E excited state of Cr3+ ions occupying sites of both cubic and tetragonal symmetry in magnesium oxide, MgO. The experiments were carried out at 1.6K, in the X-band frequency range (ν ~ 9.5 GHz) with the magnetic field parallel to the crystal [111] direction. In this orientation the optically detected magnetic resonance spectra from Cr3+ ions in cubic and tetragonal symmetry sites are well-separated in magnetic field. In addition all three resonances from the mutually orthogonal tetragonal species occur at the same magnetic field. The purpose of this geometry is to eliminate cross-relaxation between cubic and tetragonal sites.
4f-Electron-Phonon Interaction and Davydov Splitting in PrF3
Authors: Dahl M. , Schaack G.
Published: February 2023

See MB1 for summary.
Mechanisms of Exciton Trapping in Oxides
Authors: Hayes W.
Published: February 2023

See MB7 for summary.
Nondegenerate Four-Wave Mixing in CuCl
Authors: Levy R. , Tomasini F. , Grun J. B.
Published: February 2023

See TuG7 for summary.
Renormalization Effects of Exciton Polaritons in CuCl by Nonlinear Ellipsometry and Two-Photon Polarization in the Spatially Dispersive Region of Exciton Polaritons in CuCl
Authors: Kuwata Makoto , Nagasawa Nobukata
Published: February 2023

See TuG9 and TuGlO for summaries.
Emission Properties of Quantized Excitonic Polaritons in a Thin GaGs Layer
Authors: Schultheis L. , Ploog K.
Published: February 2023

See FE4 for summary.
Optical Properties of Cu+ Ions in RbMgF3 Crystals
Authors: Tanimura K. , Sibley W. A.
Published: February 2023

The optical properties of Cu+ ions in RbMgF3 single crystals have been investigated. In this material, two distinct sites are available for the Cu+ ions when they replace Rb+ host lattice ions. The symmetry of the two Rb+ sites is C3v and D3h respectively. Therefore, this crystal structure provides the opportunity to study the same ion, Cu+, in two different sites in one crystal. Two sets of optical absorption and emission bands are observed. The two sets of optical transitions are guite different in nature. In one case, the optical data suggest that there is very weak coupling between Cu+ ions and the lattice, whereas in the other case strong coupling exists. This is evidenced also by the transition lifetimes of the luminescence associated with these centers. The off-center nature of the copper ions in one lattice position give rise to interesting low temperature optical effects. These effects can be explained in terms of weak and strong lattice coupling and can be utilized to yield an energy level diagram for Cu+ ions in RbMgF3.
The Spectroscopy of Low-Ligand-Field Cr3+ in Germanium Garnets
Authors: Miniscalco W.J. , Desjardins S.R. , Andrews L.J. , McCollum B.C.
Published: February 2023

The search for tunable solid state lasers has lead to a resurgence of interest in Cr3+ -doped materials. Crystals with an intermediate or low ligand field environment for the Cr3+ ion are of particular interest because of their potential as broadly tunable, 4-level, red and near-infrared lasers. These hosts are qualitatively different from high field materials such as ruby and luminesce in a broad band because the 4T2 state is comparable or lower in energy than the 2E state. We present the results of optical and electron paramagnetic resonance (EPR) spectroscopic investigations of a family of Cr3+ -doped germanium garnets with the formula Ca3M2(GeO4)3, where M = Al, Ga, or Sc. The Cr3+ ion substitutes for the M3+ and occupies a site of distorted octahedral symmetry. We have found significant variation among these three germanates with regard to ligand field strength and concentration quenching for Cr3+. Moreover, the small ionic radii of Al3+ and Ga3+ enable these analogs to form high concentrations of a native defect believed to be a complex of the F+ center. The presence of this color center makes it difficult to control the oxidation state of the Cr dopant. This defect does not form in the Sc germanate and Cr remains in the 3+ oxidation state.
Luminescence of In+ and Tl+ in Alkali Halides with the Caesium Chloride Structure
Authors: Simkin D.S. , Sivasankar V.S. , Jacobs P.W.M.
Published: February 2023

Phosphors formed from alkali halides with the CsCl structure that contain activator ions with the ground-state configuration ns2, differ from their analogues with the NaCl structure in several respects. In addition to the usual A(1A1g → 3T1u), B(1A1g → 3Eu, 3T2u) and C(1A1g → 1T1u) absorption bands, a variable number (up to three) charge-transfer bands may be distinguished and in CsI:Tl+ these CT states actually lie between the 3T1u and 1T1u unrelaxed excited states instead of above 1T1u as is usually the case. In CsI:Tl+ the CT bands lie in their usual location between the C band and the absorption edge while in CsBr:In+ no CT bands are seen, presumably because the CT states overlap the intrinsic exciton states. The emission spectrum of CsBr:In+ contains three bands, none of which are CT bands. Two of these are from coexistent minima of tetragonal and trigonal (or possibly orthobombic) symmetry and the third is from the relaxed B state. The CsI:In+ emission spectrum also contains these three bands and, in addition, a fourth band that is excited only in the CT absorption band. The emission spectrum of quenched CsI:Tl+ crystals consist of three bands all of which can be excited in the A band. The coexistence of three types of minima in the adiabatic potential energy surface that represents the relaxed excited 3T1u state is a most unusual occurrence - indeed unique so far in these phosphors - and two possible models for the RES are formulated
Experimental and theoretical studies of optical properties of (Ag+)2 pairs in NaCl
Authors: Pédrini C. , Atoussi B. , Chermette H. , Moine B.
Published: February 2023

The study of the (Ag+)2 pairs in NaCl has been investigated on strongly doped single crystals grown in our laboratory by the Bridgman technics. Both experimental and theoretical aspects have been considered.
Cr3+ Induced Nucleation and Luminescence in Silicates Glasses
Authors: Champagnon B. , Durville F. , Duval E. , Boulon G.
Published: February 2023

Nucleation and growth of small particles induced by Cr3+ ion in a magneso-alumino silicate glass so called cordierite (52 % SiO2, 34.7 % Al2O3, 12.5 % MgO and 0.8 % Cr2O3) has been studied by Small Angle Neutron Scattering (1). The advantage of the Cr3+ ion is that this activator is sensitive to spectroscopic techniques such as E.P.R. and laser spectroscopy so that the different particles which develop during heat-treatment can be characterized and studied.
Luminescence from LiGa5O8 : Co2+
Authors: Donegan J. F. , Bergin F. J. , Imbusch G. F. , Remeika J. P.
Published: February 2023

Crystals of cobalt doped LiGa5O8 have a deep blue colour and the absorption spectrum is characteristic of Co2+ in tetrahedral sites. The cobalt ions enter tetrahedral gallium sites in this material. The strong absorption in the visible is due to the 4A2→ 4A1 (4P) transition which peaks at around 16,000 cm-1. Luminescence occurs in the red and near infrared. In this material the 4A1 (4P) level lies below the 2E(2G) level and consequently the luminescence occurs from the 4A1 state. These luminescence transitions are thus spin-allowed and, since the tetrahedral site lacks inversion symmetry, the transitions occur by an electric dipole process - the lifetime at 77 K is around 200 ns. At low temperatures the 4A2→ 4T2 (4P) luminescence and absorption transitions are characterized by a sharp strong zero-phonon line. At higher temperatures the fine structure is lost, and the luminescence shows up as a broad band.
Facile Nonphotochemical Hole Buring and Filling of Laser Dyes and Rare-Earth Ions in Deuteroxy and Hydroxy Polymers
Authors: Fearey Bryan L. , Carter Thomas P. , Small Gerald J.
Published: February 2023

See WE22 for summary.
Theory of the Nonlinear Optical Properties of Semiconductors
Authors: Haug Hartmut
Published: February 2023

The optical spectra of laser-excited semiconductors change with varying laser intensity. Close to exciton or biexciton resonances these optical nonlinearities are, e.g., large enough to obtain optical bistability. The cause for these large nonlinearities are many-body effects in the system of the electron-hole pair excitation. The use of nonequilibrium Green’s functions, or if a quasi-equilibrium exists of thermal Green’s functions, makes it possible to take radiative and Coulomb interactions consistently into account.
The Source of Multimode Instabilities in Homogeneously Broadened Lasers
Authors: Hillman Lloyd W. , Koch Karl
Published: February 2023

Multimode instabilities result from a parametric coupling of off-resonant cavity modes. We will present a series of numerical and analytic calculations that clarify the nature of the coupling.
Intrinsic Oscillations and Multistability in the Trasmission of a Na Vapor filled Fabry-Perot in absence of a Buffer Gas.
Authors: Salieri P. , Giusfredi G. , Cecchi S. , Arecchi F.T.
Published: February 2023

In previous experiments on the trasmission properties of a Fabry-Perot interferometer filled with Na vapor |1,2| a buffer gas was added to collisionally broaden the resonance, with velocity changing collisions inducing broad ground state pumping over the whole line. Here we consider the very different inhomogeneous regime (no buffer gas), where optical pumping takes place on single homogeneous velocity groups. We carefully control direction and strength of the magnetic field and examine the cavity transmission properties, both in intensity and polarization, in the temperature range 130 - 180 °C (0.5 - 9.2·1011 atoms/cm3), as the laser is tuned across the DI line.
Some Attempts to Understand a Very High-dimensional Strange Attractor
Authors: Ikeda K. , Matsumoto K.
Published: February 2023

In the present talk we report our recent attempts to understand the physics of a very high-dimensional strange attractor exhibited by a model of optical chaos. We show (1) how a high-dimensional attractor developes from a low dimensional one and (2) how the "interior" and the "exterior" of strange attractor may be observed in physical processes.
Overview Of Classical And Quantum Hamiltonian Chaos
Authors: Casati Giulio
Published: February 2023

In the last 30 years the studies in nonlinear dynamical systems have brought to a fairly good understanding of the statistical properties of classical dynamical systems.
Demonstration of Self-Pulsing Instabilities and Routes to Chaos in a Single Mode Homogeneously Broadened Raman Laser
Authors: Harrison R.G. , Biswas D.J. , Al-Saidi I.A.
Published: February 2023

We report huge pulsating instabilities in a single mode homogeneously broadened Raman laser. Ruelle-Taken, intermittent and period-doubling routes to chaos are observed. The laser, which uses NH3 as the active medium near-resonantly pumped on the aR(6,0) transition by a CO2 laser, emits on aP(8,0) transition at ~ 12.8 μm. This lasing transition has recently been clearly identified as Raman in origin for NH3 pressures 1 - 20 torr and pump intensity ~ 600 kW/cm2 (operating conditions for our experiment) and possesses extremely high gain ~ 10% cm−1 [1].
Frustrated optical instability: Self-induced spatial instability of polarization in nonlinear optical media
Authors: Otsuka Kenju , Yumoto Junji
Published: February 2023

Maker et al. predicted and demonstrated experimentally that the axes of vibrational ellipse for elliptically polarized light rotate as a function of distance in isotropic Kerr-like media.1 Nonlinear eigenpolarization has been predicted recently by Kaplan for interfering beams (degenerate collinear four wave mixing geometry) in isotropic Kerr-like media. 2 In this paper, we extend their analyses to anisotropic crystals and provide a new aspect to the nonlinear theory of wave propagation, that is, the deterministic spatial instability of polarization of interfering beams.
Line Competition and Line Selection in Off-Resonantly Pumped Systems
Authors: Dupertuis M.A. , Salito S.A. , Salomaa R.R.E. , Siegrist M.R.
Published: February 2023

We will show that the observed fine-structure of the HF-FIR laser can be explained theoretically. The existence of line selection rules and future possible developments will be reviewed.
Coupled Return Maps and the Problem of Two Coupled Unidirectional Single Mode Homogeneously Broadened Lasers
Authors: Lawandy N. M. , Plant D. V.
Published: February 2023

The equivalence of the mean field model for a resonantly tuned single mode homogeneously broadened ring laser and the Lorenz equations was shown by Haken in 1975[1]. Unfortunately, the conditions for observing chaotic emission require the bad cavity limit in conjunction with a large gain. Recently it was suggested by Weiss that far infrared lasers, owing to their narrow linewidths and large gains, could serve as the experimental work horse for the observation and study of optical chaos in the Lorenz system[2]. These lasers however exhibit complicated intensity dependent gain structure and therefore may introduce strong intensity dependent sidebands and inhomogeneous broadening effects[2],[3]. A key to the problem lies in the ability to drop the threshold for chaos in order that lower pump powers could result in the necessary gain for the transition to chaotic output.
Observation of Power Instability and Multimode Behavior in the UCSB Free-Electron Laser
Authors: Amir Avner , Elias Luis R. , Gregoire Dan D. , Kotthaus Jòrg , Ramian Gerald J. , Stern Avinoam
Published: February 2023

Summary not available.
Evidence of Mode Splitting in a Single Mode Homogeneously Broadened Laser
Authors: Biswas D.J. , Harrison R.G.
Published: February 2023

Recently we have demonstrated chaos in a single mode homogenously broadened two-photon Raman laser1 which possesses extremely high gain ~ 10% cm–1.2 Here we consider the oscillation periods of the pulsating instabilities also observed in this system and identify them as providing evidence of mode splitting in a single mode homogeneously broadened laser.