Optics and Spectroscopy (v.93, #4)

On the origin of the galvanomagnetic effect in Ne plasma by M. P. Chaĭka; V. A. Polishchuk; G. Ts. Todorov (489-492).
The interrelation between the width of a magnetogalvanic signal and the alignment of the highly excited level 2s 5 (4s [3/2]0) has been found experimentally.

Raman spectroscopy of topotecan, an inhibitor of DNA topoisomerase I by K. E. Mochalov; O. A. Ustinova; S. A. Strel’tsov; S. L. Grokhovskii; A. L. Zhuze; I. R. Nabiev; A. V. Sukhanova; V. A. Oleinikov (493-500).
Topotecan (TPT), a water-soluble derivative of camptothecin (inhibitor of human DNA topoiomerase I), has found wide application in cancer chemotherapy. The central problem in using topotecan is the presence of lactone rings in its molecules, which undergo hydrolysis at a physiological pH yielding an inactive and even toxic form of the drug. The analysis of Raman spectra of TPT in H2O and D2O solutions made it possible to assign the spectral bands to the vibrations of particular molecular groups. Spectral features indicative of the opening of the lactone rings of the TPT molecules, deprotonation of the hydroxyl groups in their quinoline fragments, and of possible participation of the hydroxyl and carbonyl groups in H bonding are found. The data obtained are necessary to study the molecular mechanisms of TPT-DNA interaction and the formation of ternary complexes between TPT, DNA, and DNA topoisomerase I.

Within the framework of a sufficiently general nonadiabatic model taking into account the interaction of an arbitrary finite number of electronic states and not requiring the smallness of a perturbation parameter, expressions have been obtained for the radiative lifetimes of the rovibronic levels of states of the nl complex of terms of a diatomic molecule. It is shown that the determination of ratios of the nonadiabatic and adiabatic radiative lifetimes for the rovibronic levels can be reduced to the solution of two independent problems (the determination of ratios of the adiabatic values of radiative lifetimes for the mutually perturbing states and determination of the expansion coefficients of the wave functions of rovibronic states in the Born-Oppenheimer basis set of wave functions) when the rovibronic states are perturbed by only a single rovibrational level of each electronic state or by an arbitrary number of rovibrational states of each electronic state provided that the potential curves of the combining states are similar and the dipole moments of electronic transitions weakly depend on the internuclear separation (which is quite a case for highly excited electronic states). To illustrate the efficiency of using the expressions obtained, the perturbations of the radiative lifetimes of rovibrational levels of the I 1Π g and J 1Δ g states of the 3d complex of terms of the H2 molecule were considered.

General formalism and basic ideas of the instanton method are described. The potentialities of the method are demonstrated by calculating the tunneling splitting of the ground vibrational level for nonrigid molecules with two and three equivalent minima on their potential-energy surface. Some advantages of the application of the instanton method as compared to the well-known semiclassical approximation for describing the spectra of tunneling splitting of a nonrigid molecular system are proved.

With the aim of creating a laser operating by a self-terminating transition in the blue spectral region, it is suggested to use the 6s 2 S 1/2→5p 2 P 3/2 transition at 451.1 nm in In atoms. Indium iodide was used as a donor of In atoms for an active medium in a discharge. Emission and absorption spectra of the active medium, as well as the time characteristics of pumping pulses and emission due to transitions from the resonance level of In, were measured.

The effect of anions contained in solutions on the energy transfer from Tb(III) and Dy(III) ions to different Ln(III) ions is investigated in aqueous and alcohol solutions. It is shown that the regularities revealed in the energy transfer are completely determined by the ratio between the dissociation rate of the binuclear complex and the rate of energy transfer in it. The rate constant k t of energy transfer in solutions in which labile binuclear complexes of Ln(III) ions are linked through the strong acid anions Cl, NO 3 , and HSO 4 depends on the nature of ions in the pairs. It is demonstrated that the energy transfer in all the systems predominantly occurs through the induction-resonance mechanism. The rate constants k t in aqueous solutions of weak (acetic, salicylic, and carbonic) acids also depend on the nature of ions interacting in pairs but do not correlate with the Förster overlap integral of the spectra. In labile binuclear complexes, the interaction between these ions proceeds by the exchange-resonance mechanism at a distance of ≈0.4 nm. It is established that the constants k t in alcohol solutions of Ln(III) ions are virtually independent of the nature of the pairs of the ions interacting through the acetate bridge. A comparison of the dissociation rate constants for Ln-anion complexes in alcohol solutions and the expected intracomplex rates of energy transfer in the binuclear complexes offers a satisfactory explanation of the obtained results and makes it possible to determine the association constants for binuclear lanthanide complexes in these solutions.

Determination of photodissociation anisotropy parameter β for RbI molecules by sub-Doppler spectroscopy by K. O. Korovin; A. A. Veselov; O. S. Vasyutinskii; D. Zimmermann (530-534).
The photodissociation of RbI molecules upon exposure to polarized laser radiation with a wave-length of 266 nm is investigated. The anisotropy parameter β and the parameter ζ characterizing thermal motion of RbI molecules are determined by analyzing the Doppler absorption profiles of Rb atoms (52 S 1/2) formed through photodissociation of RbI molecules. The systematic error in determination of the parameter β due to the layer thickness is examined.

Methods of spectral estimation in local nuclear quadrupole resonance with a dispersion by V. S. Grechishkin; R. V. Grechishkina; A. A. Persichkin; A. A. Shpilevoi (535-538).
The spectral estimation in local nuclear quadrupole resonance at a high noise level is performed for the first time using the modern techniques of linear prediction (LPSVD) and matrix pencil (ITMPM). The fast Fourier transform with signal accumulation does not ensure the required sensitivity in the case of weak signals when the object and the receiver of the spectrometer are spaced widely apart or when there is an effect of adverse factors (screening, interference, random disturbance, etc.), which is typical of remote monitoring in actual practice. It is demonstrated that the use of the proposed techniques considerably increases the efficiency of spectral estimation in this field of solid-state spectroscopy and, in particular, avoids the phase errors arising in usual experiments at a signal-to-noise ratio of less than 0.5.

Conditions are determined under which an external magnetic field leads to a new mechanism of formation of surface TM polaritons in crystals possessing dynamic magnetoelectric interaction and spatial dispersion simultaneously.

Conditions are determined under which an external magnetic field leads to anomalies in the spectrum of bulk TM polaritons in a crystal plate possessing simultaneously the dynamic magnetoelectric effect and spatial dispersion.

Coherent control of thermalized luminescence in semiconductor quantum dots by A. V. Fedorov; A. V. Baranov; Y. Masumoto (555-558).
A theoretical study of the time-integrated signal of thermalized luminescence excited by a pair of phase-locked light pulses shows that the idea of coherent control should be efficient for measuring the total dephasing rates of high-energy excitonic transitions. This approach can be used for studying both the homogeneously and inhomogeneously broadened systems, which is highly important in studies of the semiconductor quantum dots. It is found that the method of coherent control makes it possible not only to obtain information about the relaxation constants but also to make conclusions about the statistical properties of frequency distributions of the excitonic transitions responsible for broadening the optical spectra.

Spectroscopic properties of magnesium aluminosilicate glass-ceramics doped with divalent cobalt ions by A. M. Malyarevich; I. A. Denisov; K. V. Yumashev; O. S. Dymshits; A. A. Zhilin; A. V. Shashkin (559-566).
Electronic absorption and luminescence spectra and nonlinear optical properties of magnesium aluminosilicate glass-ceramics doped with divalent cobalt ions are studied in relation to their synthesis conditions. The lifetimes of the 4 T 1(4 P) and 4 T 1(4 F) excited levels of tetracoordinate Co2+ ions in these glass-ceramics are found to depend on the cobalt concentration and lie within the ranges from 25 to 40 and from 120 to 450 ns, respectively. Using the absorption saturation curves, the ground state absorption cross section for the wave-length of 1.54 μm is estimated to be σGSA=3.3×10−19cm2. The induced emission of the tetrahedrally coordinated Co2+ ion, which dominates over the absorption from the excited state in the spectral range from 640 to 690 nm (4 T 1(4 P)→4 A 2 transition), is found.

Squeezed states of the Jaynes-Cummings (JC) model are constructed and the statistical properties of the field oscillator in these states are studied. The presence of interaction between the field oscillator and the atom results in the appearance of slow temporal variations in the average values of the dynamic quantities. Two cases essentially differ: When only one of two modes of the JC model is excited, the variations in time, in particular, of the average value of the coordinate are governed by the mode anharmonicity. In the case when both modes of the JC model with close frequencies are excited, the temporal variations represent collapse and revival of oscillations with the frequency $$2ksqrt {n + 1} $$ , where k is the constant of the atom-field oscillator interaction and n is the number of photons. The constructed squeezed vacuum states are not two-photon states, because the probability of finding an odd number of photons is not equal to zero and varies with time.

Completely integrable models of propagation of optical pulses of different polarization are considered under Raman resonance conditions with transitions involving a change in the total angular momentum 0→0 and 1→1.

Micromaser generation of two-mode light with quantum correlation by V. N. Gorbachev; A. I. Trubilko (580-587).
Two-mode generation of light in a system of N identical relaxation-free atoms placed in a resonator is considered on the basis of the derived controlling Fokker-Planck equation for the Glauber-Sudarshan quasiprobability. Under steady-state conditions, a state of modes is formed with nonclassical correlation characterized by sub-Poison statistics of photons and leading to complete suppression of shot noise. Being an entangled pair, these sub-Poisson modes can be used as a quantum channel for teletransmission of light. In contrast to the standard Einstein-Podolskly-Rosen (EPR) channel, the recipient can reproduce only correlation functions of the intensity of an unknown state.

The transformation of the angular momentum of an optical eddy in a weakly directing perturbed optical fiber is analyzed within the spin-orbit operator representation. The case of fibers with anisotropy of the core and cladding materials and the case of fibers with an elliptic cross section are considered. The spectrum of polarization corrections to the scalar propagation constant is determined for fibers of two types. For both the strongly anisotropic and elliptic fibers, the spin angular momentum of the linearly polarized LV eddy is suppressed and the orbital angular momentum is characterized by simple oscillations with a beating length dependent only on the spin-orbit parameter of an unperturbed fiber. The orbital and spin angular momenta of the circularly polarized CV eddy in the anisotropic fiber interchange in the elliptic fiber. The orbital angular momentum can be completely restored in the strongly anisotropic fiber, whereas only the spin angular momentum is completely restored in the elliptic fiber.

A method of calculating the partial characteristics of radiation absorption by the components of light-scattering disperse layers is proposed. This method is based on statistical modeling (the Monte Carlo method). The absorptivities of photographic gelatin and silver bromide microcrystals and the corresponding distributions of the absorbed energy over the layer thickness are calculated using the example of an interaction between actinic radiation and silver halide photographic layers in the wavelength range λ=200–440 nm. The following structural parameters of the photographic layer are used in the calculation: the mean size of emulsion crystals d=0.5 μm; the polydispersity C V =25%; the volume concentrations C V =10, 20, and 30%; and the thickness of the emulsion layer H=10 μm.

Light scattering by multilayer axially symmetric particles by V. G. Farafonov; V. B. Il’in; M. S. Prokop’eva (603-609).
An exact solution to the problem of light scattering by multilayer axially symmetric particles is derived and some aspects of its computer-aided implementation are discussed. The main specific features of the solution are (i) separation of the incident, scattered, and internal fields into two parts and special selection of the scalar potentials for each of them; (ii) expansion of the potentials in terms of spherical wave functions; (iii) formulation of the problem in the form of surface integral equations; and (iv) solution of the reduced systems of the linear algebraic equations for the coefficients of the potential expansions. Mathematical justification of the solution is discussed, which is formulated in the recursive and nonrecursive form (for the T-matrix). The developed computer program has shown that the proposed approach makes it possible to consider axially symmetric particles with essentially different internal structures (i.e., with a spherical core, oblate spheroidal shell, or prolate spheroidal intermediate layer). The results of calculations of the optical properties of the multilayer nonspherical particles are presented and discussed.

The light scattering by two-dimensional photonic crystals is studied within the framework of the rigorous theory of multiple scattering based on the scattering matrix technique. Using translational properties of the vector cylindrical harmonics, the problem is reduced to a system of linear equations.As a result, the angular dependences of the scattered light intensity are calculated for different samples with a photonic-crystal structure comprised of long circular cylinders. The effects of structure and the degree of ordering of the sample on the angular characteristics of the light scattering are analyzed.

The influence of changes in the average refractive index and thickness of a working medium layer on the holographic record of sloped transmission gratings in photopolymerizable compositions (PPCs) was studied. The parameters of holographic gratings change with increasing slope of grating lines. It is shown that shrinkage of the PPC layer is the main factor influencing the direction and rate of the energy exchange between recording beams and medium during the holographic recording in PPCs.

The experimentally determined parameters of the photoresponse of a bacteriorhodopsin D96N suspension in glycerin are compared with the calculated values obtained from absorption spectra of this suspension. The kinetic parameters and saturation intensities are found to be different for the phase and amplitude components of the dynamic holographic grating in the medium under study. The effect of intermediate isomers of the photocycle of bacteriorhodopsin molecules is supposed to be responsible for the observed behavior of photoresponse. The photoresponse sensitivities and saturation parameters determined for either component of the grating from the energy transfer of the phase-modulated beams and from the spectral diagnostics of the medium are found to satisfactorily agree with each other.

Illusions of vision: Interpretation within the framework of a holographic model by V. P. Titar’; T. V. Bogdanova; M. T. Torkatyuk (631-638).
Several illusions of vision are considered on the basis of a neurophysiological holographic model of visual perception at the level of the eye’s and the retina. It is suggested that the eye’s optical system forms a spatial spectrum of the observed object rather than its image on the retina. The spectrum is encoded by active anisotropic quasi-crystalline structures of rod rhodopsins and cone iodopsins, and a complex Fourier hologram of the observed object consisting of two quadrature components is recorded. The holographic hypothesis is confirmed by the results obtained by digital simulation.

Holographic recording of thin diffraction gratings by nano-and picosecond laser pulses λ=532 nm) is studied in polymerdispersed liquid-crystalline structures based on photosensitive molecules of 2-cycloocty-lamino-5-nitropyridine sensitized with C70 fullerene. Using experimental data, nonlinear refraction n 2 and nonlinear third-order susceptibility χ(3) are calculated for the first time. The obained values determine the potential of the studied media for the modulation and frequency generation of laser radiation in the visible spectral range.

Lidar sounding of iodine molecules at low pressures by É. I. Voronina; V. E. Privalov; V. G. Shemanin (643-645).
Lidar sounding of iodine molecules were performed at pressures lower than 1 torr. The differential cross-section of fluorescence and the absorption cross-section of iodine molecules at a wavelength of 532 nm were been obtained.