Optics and Spectroscopy (v.114, #3)

Calculation of the ground state energy of neutral atoms (Z ≤ 54) by the algebraic variant of the Hartree-Fock method by Yu. B. Malykhanov; M. V. Gorshunov; S. V. Evseev; I. N. Eremkin; R. M. Chadin (321-328).
High-precision calculations of the ground-state energy of atoms He through Xe are performed in the algebraic approximation of the Hartree-Fock method. The orbital exponents of Slater-type basis functions are optimized using the second-order minimization methods, which allows the virial theorem to be fulfilled to within 10−15–10−17 for the first time. The energies of atoms calculated with rather limited basis sets are, in terms of accuracy, as good as the results obtained by using the numerical procedure for solving the Hartree-Fock equations.

Amplitude ratios of resonance maxima caused by two-photon transitions from different levels of the ground term of the samarium atom are studied experimentally and theoretically as functions of the laser-radiation field strength. The results of these studies are shown to be promising for identifying the resonance structure of three-photon ionization spectra of the samarium atom. A not yet observed excited even-parity state with energy E ≈ 36789.1 cm−1 and hypothetical values of total angular momentum J = 5, 6 has been discovered.

The orientational frequency shift of the UHF radio-optical resonance in the 87Rb vapor with a selective optical pumping by laser and lamp sources is studied experimentally and theoretically. A leading role of the tensor component of the light shift is noticed for both excitation modes, and a modulation technique of the resonance frequency orientation shift suppression is demonstrated. We show that it is necessary to ensure a constancy of the angle between the pump light direction and the external magnetic field vector when using a rubidium quantum discriminator based on moving and rotating carriers.

Simultaneous measurements of CO and CO2 at elevated temperatures are demonstrated using a single semiconductor distributed-feedback (DFB) laser near 1570 nm. Wavelength modulation spectroscopy with second-harmonic detection is used to improve the detection sensitivity and accuracy. A proper line pair near 6368.086 and 6368.330 cm−1 is selected using some line-selection criterions for the target temperature range of 300–1000 K. Normalization of the 2f signal with the 1f signal magnitude is used to remove the need for calibration and correct for transmission variation due to beam steering, mechanical misalignments, soot, and windows fouling. The CO and CO2 concentrations measurements are within 2.21% and 2.55% of the expected values over the tested temperature range of 300–1000 K. The minimum detectable concentrations of CO and CO2 at 1000 K are 80 ppm m and 153 ppm m, respectively.

Atomic structure of nickel phthalocyanine probed by X-ray absorption spectroscopy and density functional simulations by L. A. Avakyan; A. S. Manukyan; A. A. Mirzakhanyan; E. G. Sharoyan; Y. V. Zubavichus; A. L. Trigub; N. A. Kolpacheva; L. A. Bugaev (347-352).
The local atomic structure of Ni in nickel phthalocyanine was studied by K-edge X-ray absorption fine structure spectroscopy. The obtained inter atomic nickel-nitrogen distance differs from the reference X-ray diffraction data so an additional study was performed within density functional theory framework. The justification of the used theoretical approach was provided by a comparison of theoretical free electron densities of states with experimental Ni K-edge X-ray absorption near edge spectra. The refined Ni local environment retain the reference structure of the molecule except for the length of Ni-N bond which increases to 1.90 Å.

Particular features of fluorescence of jet-cooled vapor of 2,3-diazabicyclooctene by A. P. Lugovskii; V. A. Povedailo; V. A. Tolkachev; D. L. Yakovlev (353-358).
The fluorescence and fluorescence excitation spectra of azocompound, 2,3-diazabicyclo[2.2.2]oct-2-ene, have been studied using jet cooling. The violation of the mirror symmetry between the fluorescence and fluorescence excitation spectra due to an intense long-wavelength emission that manifests itself in solutions and in the gas phase cannot be eliminated even by jet cooling. It has been revealed that the bands of pure electronic and vibronic transitions are split by 0.55 cm−1, which is caused by tunneling with accompanying emission from an intermediate short-lived state and which may be the reason for the violation of the mirror symmetry of the spectra upon tunnel inversion.

Calculation of vibrational HDO energy levels: Analysis of perturbation theory series by A. D. Bykov; K. V. Kalinin; A. N. Duchko (359-367).
Series of the Rayleigh-Schrödinger perturbation theory are analyzed and summated by the example of the HD16O molecule for vibrational energy levels. Particular attention is given to determining the location of singularities-branching points corresponding to the intersection of levels in the complex plane. Numerical analysis demonstrates the divergence of the series for states involved in the Fermi resonance; however, summation by the method of Padé-Hermite approximants makes it possible to reconstruct the levels by coefficients of the series with sufficient accuracy. It is found that resonance-coupled states have common branching points, which leads to the coincidence of series’ coefficients in high orders. Branching points’ characteristics permitting one to obtain a comparatively simple representation of high order corrections are determined.

The relative intensities of lines in resonance Raman scattering spectra of isolated skatole and skatole-water complex have been calculated quantum mechanically. The influence of the intermolecular interaction on these spectra has been considered. Particular features of the intensity distribution in the resonance Raman scattering spectra of indole and skatole have been compared.

Ammonia-sensing properties of acridine immobilized in SiO2 sol-gel films by N. I. Selivanov; L. G. Samsonova; T. A. Solodova; T. N. Kopylova; E. N. Tel’minov (373-378).
The spectral and luminescent properties of acridine in SiO2 films synthesized by the sol-gel method using acid hydrolysis of tetraethoxysilane are studied. It is shown that acridine in films exists in protonated form. Ammonia-gas-sensing properties of films doped with acridine are studied by the fluorescence response (decrease in the intensity) of the protonated form. The possibility of multiple use of a sample without a noticeable decrease in its sensitivity is demonstrated. It is shown that the fluorescence response to a maximal permissible concentration of ammonia in the gas mixture with argon is 6–8%.

Broadband copper luminescence in potassium-aluminum borate glasses by N. V. Nikonorov; A. I. Sidorov; V. A. Tsekhomskii; T. A. Shakhverdov (379-383).
Broadband luminescence in the visible spectral range has been investigated for copper-containing potassium-aluminum borate glasses. It is shown that the luminescence in initial glasses (before their heat treatment) is due to the presence of molecular clusters Cu n (n < 10) in them. Chemical reactions during heat treatment lead to the formation of Cu n Cl x and Cu n O x clusters with luminescence bands lying in the spectral range of 450–600 nm.

Heating of electrons and lattice of aluminum caused by interaction with a femtosecond laser pulse is described quantitatively. Coefficients of absorption of s- and p-polarized pulses are calculated. Frequencies of electron-electron collisions in aluminum are determined from comparison of experimentally measured and calculated coefficients of absorption.

In the low-temperature (4.2 K) excitonic light reflection spectra of CdSe crystals subjected to the low-energy (several keV) electron irradiation, an effect of the stop of a “rotation” at the longitudinal exciton frequency is found. The connection of this effect with Fermi level pinning on the surface of the semiconductor is assumed.

Birefringence of PbGa2S4 crystals by V. N. Kamenshchikov; V. A. Stefanovich; L. M. Suslikov (394-396).
Birefringence of PbGa2S4 single crystals is studied in the spectral range of 0.45–0.8 μm at T = 300 K. The obtained results are analyzed, and conclusions on the bond character in lead thiogallate are drawn.

Local surrounding of vanadium atoms in CuCr1 − x V x S2: X-ray absorption spectroscopy analysis by Yu. O. Smirnova; N. Yu. Smolentsev; A. A. Guda; M. A. Soldatov; K. O. Kvashnina; P. Glatzel; E. V. Korotaev; A. V. Soldatov; L. N. Mazalov (397-400).
In the present work local surrounding of vanadium atoms in layered copper-chromium disulfides CuCr1 − x V x S2 is investigated using high-resolution X-ray absorption spectroscopy above vanadium K-edge. Based on experimental and theoretically simulated spectra comparison it is shown that vanadium atoms replace chromium ones even at high concentrations of vanadium and that they are in 3+ oxidation state.

Spectral-kinetic study of phototransformations of new 3-acyl-2-hetarylchromones by O. I. Kobeleva; T. M. Valova; V. A. Barachevsky; I. S. Semenova; K. S. Levchenko; V. N. Yarovenko; M. M. Krayushkin (401-405).
Spectral-kinetic and fluorescent properties of 16 new photosensitive compounds of the 2-furyl- and 2-thienyl-3-acylchromone classes, the initial nonluminescent forms of which undergo irreversible phototransformations into fluorescent products, are considered on the basis of their structure and properties responsible for the possibility of their application as photosensitive components of recording media for archive optical disks.

Cross luminescence of BaF2 crystal: Ab initio calculation by A. S. Myasnikova; A. S. Mysovsky; E. A. Radzhabov (406-413).
Using ab initio methods and taking into account the lattice relaxation and polarization caused by the occurrence of the core hole, we have studied theoretically the cross luminescence in barium fluoride crystals in terms of the embedded-cluster approach. Two schemes of modeling of the core hole have been performed—in the form of an additional point charge and in the form of the 5p state of the barium ion. Calculations have been done both by the Hartree-Fock method and by the density functional method. We have showed that the deformation of the lattice caused by the occurrence of the core hole leads to states localized on fluorine ions of the nearest environment splitting off from the valence band of the BaF2 crystal. The cross-luminescence bands at 5.7, 6.3, and 7.1 eV are caused by transitions from these localized states. We have also showed that the low-energy edge of the cross luminescence is formed by transitions from states that are localized on ions of the second coordination sphere.

Properties of evanescent waves in polarized media in a constant external electric field: II. The noncompensated antiferromagnetic by D. V. Kulagin; G. G. Levchenko; A. S. Savchenko; A. S. Tarasenko; S. V. Tarasenko; V. G. Shavrov (414-420).
The effect of gyrotropy on the character of formation and propagation of evanescent waves of the TM and TE types in the presence of a constant external electric field is studied by an example of the two-sublattice model of a centrally symmetric antiferromagnetic in the easy-plane, weak ferromagnetic phase.

We have constructed a solution to the problem of scattering by a nonconfocal multilayer particle. The main difficulty was to join expansions constructed in two spheroidal systems on either side of each boundary. As a result of a detailed consideration of relations between scalar wave spheroidal and spherical functions, we have succeeded in finding a representation of the former in terms of the latter and vice versa. In the final form, the joining of solutions is described by only one matrix, which depends on coefficients of representations of angle spheroidal functions in terms of associated Legendre functions of the first kind. Since the problem has been solved using an approach that involves the method of extended boundary conditions, the dimension of the system for numerical determining unknown coefficients is equal to the number of terms that are taken into account in field expansions and does not depend on the number of particle layers. Previously performed numerical calculations for confocal particles have shown a very high efficiency of the algorithm not only for particles that are close to spheres in shape, but also for strongly prolate and strongly oblate spheroids. In addition, the algorithm makes it possible to calculate optical properties of particles that have dozens of layers.

We have presented the results of our investigations of relative changes in the intensity of light scattered by nanodisperse systems that are exposed to the action of an electric field. To orient particles of the systems under study, sinusoidal fields of variable amplitude and frequency from the radiofrequency range were used. We have examined aqueous polydisperse suspensions of diamond and graphite particles. The average sizes of particles in the two suspensions are close to each other and are comparable with the wavelength of the incident light. Graphite particles had the shape of disks, while polycrystalline diamond particles did not have a clearly pronounced shape. Investigations have been conducted not only in the regime of a stationary orientational order of particles in the field, but also in the course of forced and free relaxation of this order. For the graphite nanodisperse system, the normalized-in-amplitude dependences of observed electrooptical effects on the field strength almost do not depend on the scattering angle, whereas, for the diamond nanodisperse system, they considerably vary as this angle changes. Upon relaxation of the orientational order of particles, the time dependences of these effects in both systems change with varying scattering angle. We have compared field and time dependences of scattering-induced effects with analogous dependences of field-induced dichroism.

As initial data, optical polarization tomography of tensor and vector fields uses ray integrals the values of which are determined from polarization measurements. Most algorithms of integrated photoelasticity are based on the linear approximation of the solution of the birefringence equations. In this work, the approximation of smooth rotation of quasi-principal axes of the polarization tensor is proposed for use in approximating values of ray integrals.

An analytical solution of the problem of description of surface plasma oscillations at an arbitrary relation between the mean free path of electrons and film thickness is obtained for thin metal films, the thickness of which does not exceed the skin layer. The case of mirror-diffusive boundary conditions is considered. The wavevector dependence of the frequency of surface plasma oscillations is derived.

1D and 2D spatial distributions of a complex degree of coherence are obtained using numerical simulation for the broadband dispersed laser beams. The configuration of the spatial inhomogeneities (speck-les) of the degree of coherence is studied at various spectral widths and dispersions of the beam. It is shown that the speckle size increases with increasing distance from the initial plane where the light field is assumed to be spatially coherent. The small- and large-scale structures of the degree of coherence are shown for the transverse cross section of the beam. The results are compared with the analytically calculated correlation functions of the spatial coherence. The features of the speckle structure are interpreted using the concept of partial speckles.

Laser diode and pumped Cr:Yag passively Q-switched yellow-green laser at 543 nm by Y. Yao; Zhao Ling; B. Li; D. P. Qu; K. Zhou; Y. B. Zhang; Y. Zhao; Q. Zheng (459-462).
Efficient and compact yellow green pulsed laser output at 543 nm is generated by frequency doubling of a passively Q-switched end diode-pumped Nd:YVO4 laser at 1086 nm under the condition of sup-pressing the higher gain transition near 1064 nm. With 15 W of diode pump power and the frequency doubling crystal LBO, as high as 1.58 W output power at 543 nm is achieved. The optical to optical conversion efficiency from the corresponding Q-switched fundamental output to the yellow green output is 49%. The peak power of the Q-switched yellow green pulse laser is up to 30 kW with 5 ns pulse duration. The output power stability over 8 hours is better than 2.56% at the maximum output power. To the best of our knowledge, this is the highest watt-level laser at 543 nm generated by frequency doubling of a passively Q-switched end diode pumped Nd:YVO4 laser at 1086 nm.

A possibility for an increase in the signal-to-noise ratio in the laser spectroscopy that is free of Doppler broadening and is based on the saturated absorption is considered. The application of the counter-propagating laser beams in the multimode regime is proposed. The number of atoms that effectively interact with the field, and, hence, the intensity of a narrow resonance in the line shape can be increased due to the interaction of the counterpropagating modes with different frequencies. It is demonstrated that, for the intrinsic photon noise, the signal-to-noise ratio can be increased by a factor of √N, where N is the number of modes. For the remaining noises (fluctuations of the radiation power, noise of photodetector, etc.), the signal-to-noise ratio can be increased by a factor of N.

All-solid-state continuous-wave frequency doubling Nd:LuVO4/LBO laser with 2.17 W output power at 543 nm by B. Li; L. Zhao; Y. B. Zhang; Q. Zheng; Y. Zhao; Y. Yao (467-470).
Efficient and compact green-yellow laser output at 543 nm is generated by intracavity frequency doubling of a CW diode-pumped Nd:LuVO4 laser at 1086 nm under the condition of suppressing the higher gain transition near 1064 nm. With 16 W of diode pump power and the frequency-doubling crystal LBO, as high as 2.17 W of CW output power at 543 nm is achieved, corresponding to an optical-to-optical conversion efficiency of 13.6% and the output power stability over 8 hours is better than 2.86%. To the best of our knowledge, this is the highest watt-level laser at 543 nm generated by intracavity frequency doubling of a diode pumped Nd:LuVO4 laser at 1086 nm.

Compact low-cost detector for in vivo assessment of microphytobenthos using laser induced fluorescence by A. B. Utkin; S. Vieira; J. Marques da Silva; A. Lavrov; E. Leite; P. Cartaxana (471-477).
The development of a compact low-cost detector for non-destructive assessment of microphytobenthos using laser induced fluorescence was described. The detector was built from a specially modified commercial miniature fiber optic spectrometer (Ocean Optics USB4000). Its usefulness is experimentally verified by the study of diatom-dominated biofilms inhabiting the upper layers of intertidal sediments of the Tagus Estuary, Portugal. It is demonstrated that, operating with a laser emitter producing 30 mJ pulses at the wavelength of 532 nm, the detector is capable to record fluorescence signals with sufficient intensity for the quantitative biomass characterization of the motile epipelic microphytobenthic communities and to monitor their migratory activity. This paves the way for building an entire emitter-detector LIF system for microphytobenthos monitoring, which will enable microalgae communities occupying hardly accessible intertidal flats to be monitored in vivo at affordable cost.

Heat action of pumping radiation on a chalcogenide glass microcylinder by L. G. Astafyeva; G. P. Ledneva (478-483).
The character of the intensity distribution inside a cylindrical microparticle of chalcogenide glass is established to be nonuniform and determined by the cylinder radius. Depending on the microcylinder radius, regions of maximal intensities of the internal field are located in the illuminated or shadow parts of the cylinder (or in both the parts simultaneously) near the surface of the cylindrical particle and can exceed the incident radiation intensity by a factor of 2–4 as R < 2 μm. Heating occurs first in the shadow part of the microcylinders, then in both parts simultaneously, and then only in the illuminated part of the cylinders near their surface. This depends on the microcylinder radii and is caused by the manifestation of optical properties of the microcylinder substance and by the action of the heat transfer mechanism.