Optics and Spectroscopy (v.112, #1)

Nonresonance Compton scattering of an X-ray photon by a Ni-like atomic ion by A. N. Khopersky; A. M. Nadolinsky; K. Kh. Ikoeva; O. A. Khoroshavina; A. S. Kasprzhitskii (1-7).
The absolute values and the shape of the double differential cross section for nonresonance Compton scattering of an X-ray photon by an atomic ion with d symmetry in the core are studied theoretically beyond the impulse approximation for the example of the Ni-like atomic ions Zn2+, Kr8+, and Mo14+. It is established that, as the nuclear charge of an ion increases, (a) in all the scattering channels, the leading harmonics of transition to states of the continuous spectrum are concentrated and (b) the integral intensities of nonresonance Compton scattering are increasingly redistributed to the energy region of resonance Lands-berg-Mandelstam-Raman scattering between the threshold of termination of the Compton profile and the line of elastic (Thomson and Rayleigh) scattering. The calculated results are predictive in character.

Polarized fluorescence of jet-cooled molecular iodine by N. A. Borisevich; A. P. Blokhin; V. A. Povedailo; D. L. Yakovlev (8-14).
The degree of polarized fluorescence of molecular iodine 127I2 cooled in a supersonic jet under rotationally selective excitation in the electronic transition B 3Π 0u + -X 1Σ g + has been measured and calculated. It was found that the interaction of the angular momentum of the molecule with the nuclear spins of iodine atoms leads to a considerable depolarizing effect. This effect is most pronounced for small rotational quantum numbers of the angular momentum that are comparable with the total nuclear spin of the iodine molecule, which is equal to 5.

Investigation of highly excited states of samarium by A. I. Gomonai; E. Yu. Remeta (15-23).
Highly excited even-parity states of the samarium atom in the range between 34104 and 39155 cm−1 have been studied by the method of one-color three-photon resonance ionization spectroscopy. The energies and total angular momenta of 342 states have been determined. Seven new even-parity states of samarium have been discovered.

In the model of parabolic trajectories, expressions are derived for the bi-resonance functions that appear in the theory of collisional broadening of molecular spectral lines in the case of their interference. The functions required for calculating the cross-relaxation parameters of molecular spectral lines in the case of their broadening by rare gas atoms are obtained numerically in the model of exact trajectories for the isotropic Lennard-Jones 6–12 potential. Analytic models are proposed for these functions, and the corresponding parameters are obtained.

Intracavity laser spectroscopy of CH4 and NH3 gases by using a pulse-periodic Cr2+:ZnSe laser by N. G. Zakharov; A. P. Savikin; V. V. Sharkov; O. N. Eremeykin (32-35).
The results of studying the characteristics of an intracavity laser spectrometer based on a polycrystalline Cr2+:ZnSe laser operating in a pulse-periodic regime with the pulse-repetition rate of 3 kHz and pulse duration of ∼50 ns are presented. Intracavity spectra of absorption of NH3 and CH4 gases in the vicinity of 2.35 μm are measured. The estimate of the spectrometer sensitivity is provided.

We have studied spectral and amplitude-time characteristics of the emission by nitrogen, air, and the N2-CH4 mixture upon excitation by nanosecond and microsecond high-voltage discharge pulses in an inhomogeneous electric field in the pressure range of 0.01–3 atm. In the pulsed and pulse-periodic discharge regimes, we have observed emission bands of the violet system of cyan, the transition B 2Σ+X 2Σ+, which were comparable in intensity with bands of the (2+) system of nitrogen. We show that, in the pulsed regime, the highest intensity of the violet system of cyan is observed in the N2-CH4 mixture. We show that, in the pulse-periodic discharge in nitrogen with a small amount of a carbon-containing admixture, upon contracting the discharge, the efficiencies of formation and emission of the violet system of cyan considerably increase. We confirm that admixtures of oxygen to nitrogen lead to suppression of the emission of the violet system of cyan molecules.

Nonresonance Compton scattering of an X-ray photon by an atom with the core of the d symmetry by A. N. Khopersky; A. M. Nadolinsky; K. Kh. Ikoeva; O. A. Khoroshavina (44-49).
Using the Zn atom as an example, beyond the scopes of the impulse approximation and the incoherent scattering-function approximation, we study the absolute value and the shape of the double differential nonresonance Compton scattering cross section of an X-ray photon by an atom with the core of the d symmetry. We take into account the effects of radial relaxation of shells in the field of core vacancies and of elastic (Thomson and Rayleigh) scattering. Calculation results have a predictive character and, for the incident photon energies of 14.93 and 22.10 keV and the scattering angles of 141° and 133°, agree well with experimentally determined values of the differential Compton scattering cross section.

The electron-impact excitation of doublet D-levels of the lutetium atom is studied by the method of extended crossing beams. At the exciting electron energy of 50 eV, 64 excitation cross sections are measured. In the electron energy range of 0–250 eV, nine excitation optical functions are recorded. The occurrence of perturbations in the spectral series 6s 2(1 S)6p 2 P 1 2/○ − 6s 2(1 S)nd 2 D 3/2 is discussed.

Spectral dependence of polarization of cesium atoms during pumping by a narrowband semiconductor laser by S. P. Dmitriev; N. A. Dovator; V. A. Kartoshkin; A. I. Okunevich (56-59).
It is found in an experiment with narrowband laser pumping of Cs atoms by light of the D 2-line that the spectral dependence of the polarization of atoms significantly differs from the spectral dependence of the light absorption by nonpolarized atoms. The difference lies in a partial resolution of the hyperfine structure of the excited 62 P 3/2 state, which remains unresolved in the case of nonpolarized atoms. The shape of the spectral dependence of the atom polarization observed upon pumping with circularly polarized light differs from that in the case of the linear polarized pumping and depends strongly on the buffer gas pressure, which allows one to obtain experimental information on collisional relaxation in the excited state. Calculation for a cell with antirelaxation coating and a cell with helium (6-Torr pressure) gives spectral dependences that are qualitatively consistent with experiment.

The stability of four-particle molecules m 1 + m 2 + m 3 m 4 with unit charges of particles is studied for different masses of the particles. It is shown that all molecules containing two like particles with masses m 3 = m 4 are stable against dissociation. Their stability results from the stability of symmetric molecules with m 1 = m 2 and m 3 = m 4 and from the stability of molecules with masses of particles m 3 = m 4 and m 1 = ∞ containing one infinitely heavy particle.

Electrooptical properties of aqueous suspensions of nickel hydrosilicate nanotubes by A. V. Voitylov; V. V. Vojtylov; I. S. Dolgov; S. A. Klemeshev; E. N. Korytkova; T. P. Maslennikova; M. P. Petrov; L. N. Pivovarova (64-71).
We present the results of our investigations of electrooptical effects that occur as a result of light scattering by an aqueous polydisperse system the disperse phase of which consists of nickel hydrosilicate nanotubes with a chrysotile structure. Multilayer nanotubes were synthesized by the hydrothermal method and had the composition Ni3Si2O5. The dimensions of nanotubes were as follows: the length was 0.1–1 μm or more, the outer diameter was 10–15 nm, and the inner diameter was 3 nm. We have studied relative changes in the intensities of light transmitted and scattered by the suspension that were caused by the orientation of nanotubes in an external electric field. Experiments have been performed at different directions of the linear polarization of the incident and scattered light, different scattering angles, and different degrees of orientation of nanotubes along the field. These measurements allowed us to determine the magnitude of electrooptical effects, such as the conservative dichroism, the light scattering, and the influence of the orientation of nanotubes in the field on the intensity and degree of depolarization of light scattered by them. Curves of free relaxation of electrooptical effects and their field dependences allowed us to determine the distributions of nanotubes and their aggregates in the colloid over lengths and polarizability anisotropy values. The dependences of the degree of depolarization of the scattered radiation on the scattering angle and the relaxation dependences of electrooptical effects allowed us to characterize the aggregation stability of nanotubes in water.

Numerical simulation of energy relaxation processes in a ZnMoO4 single crystal by A. E. Savon; D. A. Spassky; A. N. Vasil’ev; V. V. Mikhailin (72-78).
We present the results of our experimental investigation and numerical simulation of excitation-energy relaxation processes in zinc molybdate crystals. We show that our kinetic model of the energy relaxation makes it possible to describe basic features of experimental results. Using this model, we estimate the trap concentration in ZnMoO4 upon irradiation of the crystal by VUV synchrotron radiation and X-ray radiation. We conclude that prolonged phosphorescence of ZnMoO4 that is observed after irradiation of the crystal by X-ray radiation can be caused by the occurrence of additional traps with a low activation energy.

Spectra and color centers of strontium titanate crystals by N. A. Kulagin; E. Hieckmann (79-86).
The results of studying the spectral properties of strontium titanate single crystals (grown under different conditions), both pure and activated by iron-group or lanthanide ions, are presented. The data on the main color centers and the formation of systems of ordered crystallites from 10−7 to 10−9 m in size on the sample surface after treatment in plasma are obtained by optical and X-ray spectroscopy, cathodoluminescence, electron microscopy, and atomic-force microscopy.

In this paper, the influencing factors on rapid flame atomic absorption spectrometry analysis of gold-loaded carbon, granularity and moisture content are discussed. The main errors came from three aspects. One was the inhomogeneity of gold distribution in activated carbon. The other was moisture content. The last one was the error from the determining process by flame atomic absorption spectrometry. The relationship between granularity, moisture content and the inhomogeneity of gold content was investigated by analysing real gold-loaded carbon samples. The results shows that the nonuniformity of distribution of moisture content and gold content could be eliminated if the granularity of gold-loaded carbon is higher than 74 microns. After the operating parameters of atomic absorption spectrometry were optimized, the error in the process of determining gold by FAAS was reduced. The results sampled by the proposed method are consistent with the iodimetric analysis. The accuracy of this method is investigated by adding gold standard as well. The recoveries are in the range of 91-97%. Our results indicate the improvement of the gold-loaded carbon analysis.

Exciton absorption spectrum of thin CsPbI3 and Cs4PbI6 films by O. N. Yunakova; V. K. Miloslavskii; E. N. Kovalenko (91-96).
A method for preparing thin films of CsPbI3 and Cs4PbI6 complex compounds has been developed. Their absorption spectrum is investigated in the energy range of 2–6 eV at temperatures from 90 to 500 K. It is found that the CsPbI3 compound is unstable and passes to the Cs4PbI6 phase upon heating at T ≥ 400 K.

Optical absorption in layered MnGaInS4 single crystals by N. N. Niftiev; O. B. Tagiev (97-100).
Optical absorption in MnGaInS4 single crystals has been studied. Direct and indirect optical transitions are found to occur in the range of photon energies of 2.37–2.74 eV and in the temperature range of 83–270 K. The temperature dependence of the band gap has been determined; its temperature coefficients E gd and E gi are −5.06 × 10−4 and −5.35 × 10−4 eV/K, respectively. MnGaInS4 single crystals exhibit anisotropy in polarized light at the absorption edge; the nature of this anisotropy is explained.

Optical absorption and exciton-phonon interaction in solid solutions Cu6PS5I1 − x Cl x by I. P. Studenyak; V. E. Ponomarev; M. Kranjcec; V. Yu. Izai; L. M. Suslikov (101-105).
We have studied the optical absorption edge of solid solutions Cu6PS5I1 − x Cl x at high absorption levels in the temperature range of 77–320 K. In a superionic state, we have revealed the Urbach behavior of the absorption edge, determined its parameters, and studied their temperature and concentration variations. We consider exciton-phonon interaction as a mechanism by which the Urbach bundle is formed and show that this bundle can be described in terms of the Dow-Redfield model.

Within the three-band model of a crystal, we calculated the probabilities of forbidden-allowed four-photon transitions between the valence band and the conduction band under conditions of two-photon resonance on the adjacent transition between two conduction bands. We show that the transformation of the electronic band spectrum under the action of high-power light of a prebreakdown intensity leads to a nonmonotonic dependence of the rate of photogeneration electron-hole pairs on the radiation intensity. We determined conditions under which a small change in the intensity in the range 1011–1013 W/cm2 leads to an increase in the generation rate of electron-hole pairs by more than an order of magnitude, which can cause an increase in the number of nonequilibrium carriers to values sufficient to trigger processes of destruction of the material.

Wave packet dynamics in a nonlinear tunnel-coupled structure of right- and left-handed media by E. I. Barykina; I. O. Zolotovskii; D. I. Sementsov (114-121).
The dynamics of a wave packet formed by tunnel-coupled forward and backward waves in a waveguide structure consisting of media with different signs of real parts of their refractive indices is investigated. Expressions for coupled-wave amplitude and reflection and transmission coefficients that are corrected for absorption are derived in the linear approximation. The expressions governing the wave-packet duration and propagation velocity of its envelope maximum are derived, taking into account the second-order dispersion, cubic nonlinearity, and dispersion of the nonlinearity. The possibility of efficient control of the forward wave velocity by applying an external magnetic field is demonstrated.

Scattering matrices of an aqueous suspension of quartz were measured at a wavelength of 0.63 μm in the scattering angle range of 10°–150°. The angular dependences of matrix elements were measured with a laser polarimeter the optical scheme of which contained two electro-optical modulators. The results of measurements were compared with the data of calculation for scatterers having the shape of prolate ellipsoids. It was shown that, under conditions of wide distribution of particles by size and at a dimensional parameter value of 2.1, the uncertainty of the shape of the distribution leads to an increase in the error of the retrieval of the parameters of the suspension particle distribution.

Numerical study of paraxial beam formation by A. V. Permyakov (129-134).
A method for numerical study of different integral problems with sufficiently strongly localized solutions is considered. Approximations of the solution with different degrees of accuracy were constructed and, using the existing approximation, an approach to an increase of the solution accuracy is proposed. Numerical solutions are obtained for the problem of free oscillations of laser cavities the optical surface of which was approximated by polynomials of the second and fourth degree inclusive. The obtained numerical solutions were stable.

The transmission spectrum of a plane-parallel MgO plate was investigated in the range of an absorption edge. The transmission intensity was approximated using the dispersion equation of the dielectric permittivity for a single oscillator taking into account relaxation. Consideration of the relaxation terms characterizing the interaction with incident radiation results in better agreement with experiment.

The theory of the interaction of electromagnetic radiation with a metal film placed between two dielectric media is generalized.

Birefringence in leucosapphire plates by V. N. Vetrov; B. A. Ignatenkov (145-147).
Modification of leucosapphire by inhomogeneous plastic deformation makes it possible to obtain plates with a varying inclination angle of the optical axis of the crystal to the surface. We have considered the light refraction in a plate upon perpendicular incidence of a parallel beam of rays.

The possibility of using the derivative transform method in reflectance spectroscopy is analyzed. It is shown that the first derivative of the external-reflectance spectrum obtained under near normal-incidence conditions allows straightforward determination of the position of the absorption-band maximum for low-intensity bands.