Vol 120, No 5 (2016)

The Rayleigh–Schrödinger perturbation theory of high orders and the algebraic Padé–Hermite approximants are used to determine the singular points of a vibrational energy function of the formaldehyde molecule dependent on a complex perturbation parameter as on the argument. It is shown that the Fermi, Darling–Dennison, and other higher-order vibrational resonances are related to Katz’s points—common branch points on the complex plane of the energy of two vibrational states. Analysis of Katz’s points that connect different vibrational states allows one to reveal essential resonance perturbations, to introduce an additional classification for them, and to determine the polyad structure of an energy spectrum.

The molecular structure of 3-Aminocoumarin was determined by conformational analysis. Conformational space was scanned by conformer distribution option of Spartan 08 program package using Merck Molecular Force Field (MMFF) method. Then obtained conformers were optimized by B3LYP/6-311++G(d, p) and B3LYP/6-311G(d, p) levels of Density Functional Theory. As a result of these calculations, only one conformer was determined. Vibrational frequencies of this conformer were calculated by Gaussian 03 program package using the same levels of geometry optimizations. The FT-IR and Raman spectra of 3-Aminocoumarin were recorded and compared with the calculated values. Consequently, a good agreement between experimental and the calculated values were founded. Molecular electrostatic potentials (MEPs), HOMO-LUMO energies, thermodynamic properties and Mulliken atomic charges were also covered in this study.

The title compound (II), 1-(cyclohexylmethyl)-2-(pyridin-2-yl)-1H-benzo[d]imidazole (C₁₉H₂₁N₃), was synthesized via N-alkylation of 2-(pyridin-2-yl)-1H-benzo[d]imidazole (I). Both compounds I and II were characterized by IR, NMR and UV-vis spectroscopy. Solid-state structure of compound II was determined by single-crystal X-ray diffraction technique. Furthermore, quantum chemical calculations employing density functional theory (DFT/B3LYP) method with the 6–311++G(d, p) basis set were performed for the theoretical characterization of the molecular and spectroscopic features of the compounds. Using the TD-DFT method, electronic absorption spectra of the compounds have been predicted at same level. When the obtained results were compared with the experimental findings, it is seen that theoretical results support the experimental data and a good agreement exists between them.

Quantum-mechanical calculations of the intensity distribution in the resonant Raman scattering spectra of aqueous solutions of tyrosine excited by laser radiation with wavelengths of 244, 229, 218, 200, and 193 nm, as well as in the nonresonant Raman scattering spectrum excited at a wavelength of 488 nm, are performed. Satisfactory agreement is achieved between the calculation results and the experimental data. It is shown that the changes in the intensity distribution observed in the spectra with a change in the excitation wavelength from 244 to 193 nm correlate with the determined changes in the contribution made by excited electronic states into the scattering tensor components. It is noted that it is necessary to take into account the Herzberg–Teller effect and that the number of excited electronic states taken into account considerably affects the calculated relative intensities of lines. The possibility of existence of several tyrosine conformers in aqueous solution at room temperature is shown.

A topological defect in a carbon nanotube grown by chemical vapor deposition from methane onto a silicon substrate with thermal oxide has been investigated and visualized (with a resolution of about 1.5 μm) by confocal Raman spectroscopy. Vibrational Raman spectra of molecular fragments of a single-wall carbon nanotube (SWCNT) without a defect and with Stone–Wales defects (two pentagonal and two heptagonal cells) are calculated. The influence of defects on the shape of G-band components (G⁺ and G^–), which makes it possible to determine the nanotube conductivity type, is considered.

Cadmium oxide CdO nanostructured thin films are synthesized using sol-gel spin coating method. The prepared samples of CdO thin films are irradiated with 10 mJ laser from pulsed Q-Switched Nd:YAG laser at 1064 and 532 nm wavelength. The samples were exposed to 45 pulses of 7 ns pulse duration. Morphology and structural analysis were carried out with scanning electron microscope (SEM) micrographs and X-ray diffraction (XRD) patterns. Optical investigations were obtained with spectrometer and fluorospectrometer from Shimadzu. SEM micrographs confirm the nanostructure of the CdO film and indicate agglomeration of nanoparticles with laser irradiation. XRD patterns show decrease in the intensity of orientation peaks after laser irradiation. Variation in band gap energy, absorption peaks, and photoluminescence spectra with laser irradiation are observed.

Particular features of the emission of radiation by a Raman-active medium excited by a sequence of ultrashort superluminal pulses have been studied theoretically. It is shown that such an excitation gives rise to the possibility of obtaining unipolar rectangular videopulses the duration and amplitude of which depend on the velocity of propagation of the excitation over the medium.

Various laser-produced metal plasmas were used for high-order sum and difference harmonic generation using the mixing of tunable mid-infrared pulses from optical parametric amplifier and 810 nm ultrashort pulses. We show that, regardless of non-optimal spatio-temporal overlap of two sources of radiation in the plasmas, the application of proposed technique allows a significant growth of harmonic yield and broadening of the number of different combinations of interacting waves in the extreme ultraviolet region, which could be useful for observation of the resonance induced enhancement of some frequency components.

The reflection of light rays by a reference microsatellite of new design, which moves with a velocity of 7500 m/s along a near-Earth orbit with a radius of 835 km, is calculated. The microsatellite is a bilayer Luneburg lens with an outer radius of 85 mm. The process of propagation of electromagnetic radiation in a Luneburg lens is analyzed for the first time with the effects of electrodynamics of moving media and optical glass dispersion taken into account. It is demonstrated that the lens motion leads to additional deflection and mixing of rays with various angles of incidence. The obtained results allow one to improve the accuracy of determination of satellite coordinates and open up new opportunities for tests of the theory of relativity and electrodynamics.

We have investigated the transmission ability of a layered structure the central layer of which is made of a “left-handed” material (its refractive index is negative) and is separated by two air slabs from a “right-handed” dielectric medium that surrounds the structure. We consider tunneling of energy fluxes through the structure and determine conditions for the complete (reflectionless) transmission of the power of the incident wave through it. We show that this effect is resonant and is observed when the tangential component of the wave vector of the incident wave coincides with the longitudinal wave vector of one of waveguiding eigenmodes of the left-handed layer.

Characteristics of parametric generation of an electromagnetic field in a cavity with oscillating mirrors have been calculated as functions of the oscillation frequency detuning from the resonant frequency for different types of frequency dependence of the cavity mirror reflectance. The influence of the initial field distribution in the cavity on the parametric generation efficiency is demonstrated.

A spectrophotometric method of determining the optical constants of materials is proposed that is based on the correction of absorption in spectra. With this method, specimens of silicon of different grades have been examined. The refractive index and the absorption coefficient of silicon in the spectral range of 30–10000 cm^–1 have been determined.

Quantum fluctuations in a laser with two different relaxation times are considered, i.e., transverse (polarization relaxation) and longitudinal (population relaxation) in the case in which the cavity transmission band half-width is much smaller than the transverse width and much larger than the longitudinal one. The lasing frequency detuning from the transition frequency of a two-level system is assumed to be arbitrary in this case, and it is necessary to take into account the contribution of two-particle correlators into the dispersion and laser linewidth. The results are considered as applied to a semiconductor laser.

UV absorption spectra of polychlorobiphenyls in transformer oil have been studied. We have shown that the absorption of the corresponding bands decreases with the growth of the time of irradiation. At t = 40 min, the degree of transformation of Abs is up to 40–66%.