Role of highly efficient collisions in collisional transfer of vibrational energy in benzophenone-foreign gas mixtures

Collisional losses of vibrational energy in mixtures of benzophenone excited by nitrogen laser radiation (λ=337 nm) and foreign gases (Ar, Kr, SF₆, C₅H₁₂) were studied by time-resolved delayed luminescence. It is established that the intensities and rates of decay of the fast and slow components of delayed luminescence can be used to evaluate the characteristics of V–V– and V–T–transfer of vibrational energy. For the V-V-process, the efficiencies and mean energies transferred in a collision are determined. It is shown that in the mixture with multiatomic gases, vibrational equilibrium is reached after a few collisions, the number of which decreases as the molecule of the foreign gas becomes more complicated. The V–V–process is characterized by high efficiencies of collisions typical for “supercollisions”. The experimental characteristics of V-V-transfer correlate well with ergodic transfer of vibrational energy predicted by statistical theories. 0120 0126 V 3 Institute of Molecular and Atomic Physics of the National Academy of Science of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 340–345, May–June, 1998.     

Anharmonic analysis of vibrational states for five-membered heterocyclic compounds

We have used the DFT/B3LYP method with 6-31G*(**) basis sets for analysis of the vibrational spectra and geometric structure of pyrrole, furan, thiophene, and selenophene in the anharmonic approximation. We have determined the influence of resonance effects on the nature of the vibrational states. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 153–156, March–April, 2007.     

Analysis of vibrational spectra of methyl-substituted uracils in the anharmonic approximation

We have analyzed the vibrational spectra of uracil and its methyl-substituted derivatives using the DFT/B3LYP/6-31G(p,d) method, in the anharmonic approximation. We have shown that it is possible to use second-order anharmonic theory of vibrational spectra in predictive calculations for substituted uracils. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 431–436, July–August, 2006.     

Theoretical analysis of vibrational spectra of tautomeric purine forms

A theoretical analysis of vibrational spectra of purine tautomers was carried out using the DFT/B3LYP/6-31G(d)* method. The influence of intermolecular interaction in purine dimers was estimated. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 1, pp. 23–27, January–February, 2008.     

Search for and elimination of dependences between vibrational coordinates in modeling spectra of large molecules

We have investigated an algorithm allowing us to reliably identify an arbitrary number of complex linear dependences between vibrational coordinates in a molecular model of very high dimensionality. These dependences are eliminated in the step for diagonalization of the kinetic part of the vibrational Hamiltonian. We have carried out computer experiments allowing us to propose optimal rules for designing appropriate computer programs for working with a vibrational Hamiltonian of very high dimensionality. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 5, pp. 561–565, September–October, 2006.     

Ascorbic acid vibrational spectra in sulfoxide solvents

Ascorbic acid in dimethyl-and diethylsulfoxide solutions has been studied using vibrational (Fourier transform IR and Raman) spectroscopy. Noticeable changes observed in the range of S=O-group vibrations can be explained by the presence of a hydrogen bond between ascorbic acid and sulfoxides. Various types of ascorbic acid/sulfoxide hydrogen-bonded complexes were revealed based on spectral analysis data. The results showed that the ascorbic acid/dimethylsulfoxide system has predominantly one type of complexes whereas the ascorbic acid/diethylsulfoxide system can contain three types of complexes. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 653–658, September–October, 2008.     

Nuclear resonance vibrational spectroscopy of iron–sulfur proteins

Nuclear inelastic scattering in conjunction with density functional theory (DFT) calculations has been applied for the identification of vibrational modes of the high-spin ferric and the high-spin ferrous iron–sulfur center of a rubredoxin-type protein from the thermophylic bacterium Pyrococcus abysii.     

Nature of soft vibrational modes in metallic glasses

A general theory of vibrational excitations in metallic glasses is presented, based on the disclination model of the structure of solids with local icosahedral symmetry. The representation of nonorthogonal plane waves is used, which allows one to separate the diagonal terms in the Hamiltonian, and also the terms describing scattering of these waves by fluctuations of the density and the force constants, and by topological structure fluctuations. We have derived and solved the Dyson equation for the Green’s function. We have obtained an analytical expression for the density of vibrational states of the glass. The nature of the soft vibrational modes is discussed. It is shown that these modes are resonant modes, whose presence is due to the fluctuations of the density and the force constants. Special attention is given to the role of forward scattering and the nature of the spatial variation in the amplitude of the given modes. Fiz. Tverd. Tela (St. Petersburg) 41, 372–379 (March 1999)     

Role of polarity in the structure of dye-solvent intermolecular complexes

A modified ω-technique was used to analyze electronic and vibrational spectra of various organic compounds, which made it possible to reveal regularities in the arrangement of molecules in a molecular complex depending on the polarity of the components. The results of such calculations of electronic spectra of 3-aminophthalimide, 4-aminophthalimide, 3-dimethylaminophthalimide, benzophenone, 9-cyanoanthracene, and tetrapyrrole compounds in addition to vibrational spectra of acetone, dimethylcarbonate, diethylcarbonate, dipropylcarbonate, and dibutylcarbonate are discussed. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 495–502, July–August, 2008.     

Localized optical vibrational modes in GaSb/AlSb superlattices

The vibrational spectrum of short-period GaSb/AlSb superlattices in the frequency range of GaSb optical phonons is investigated in detail. Localization of transverse GaSb optical phonons in GaSb/AlSb superlattices is observed experimentally for the first time. The dispersions of TO and LO phonons in GaSb are measured. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 5, 361–364 (10 September 1996)     

Triplet-triplet transfer of electronic energy upon nonequilibrium vibrational excitation of triplet molecules

The specific features of the triplet-triplet (T-T) transfer of electronic excitation energy in a gas phase upon nonequilibrium vibrational excitation of the triplet molecules of a donor were studied for an anthraquinone-diacetyl donor-acceptor pair using the time-resolved slow fluoresence of anthraquinone and sensitized phosphorescence of diacetyl. It is shown that in the gas phase, which allows regular control of the number of collisions, competition between the processes of T-T transfer and intermolecular vibrational relaxation is observed for nanosecond time resolution. The T-T transfer rate for the molecular system investigated exceeded the rate of intermolecular vibrational relaxation k_V in the triplet state T₁ of the donor. The effectiveness of the T-T transfer of energy by vibrationally excited molecules turned out to be higher than the effectiveness of transfer by thermalized ones, but even the highest of them was much less than unity. An increase in the equilibrium temperature of vapors led to a decrease in the effectiveness of transfer for both vibrationally excited and thermalized triplet molecules, thus indicating the importance of the collisional complex in the intermolecular process studied. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 4, pp. 474–479, July–August, 2000.     

Structural dynamic models and anharmonic analysis of vibrational states of polychloro-substituted dibenzo-<Emphasis Type="Italic">p</Emphasis>-dioxin

We have analyzed the vibrational spectra of β-tetrachloro-substituted and ortho-chlorosubstituted dibenzo-p-dioxin using the DFT/B3LYP/6-31G(d) method, in the anharmonic approximation. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 21–24, January–February, 2007.     

Efficiency of stimulation of gaseous chemical reactions by a diffracted light beam whose energy is absorbed by vibrational transitions

Laser-induced reversible chemical reaction kinetics in a gas mixture with the absorption of light energy by molecular vibrational transitions is investigated by mathematical modeling. The influence of beam diffraction, the relaxation time of vibrational energy into heat, and the order of vibrational transition on the structure of the region of high absorption and on the propagation of switching waves is analyzed. The discussion applies to pulses having a duration much longer than the time of energy transfer between vibrational levels. Zh. Tekh. Fiz. 69, 65–73 (April 1999)     

High-temperature vibrational densitometer for high-pressure aggressive media

High-temperature vibrational densitometer for chemically active media was developed. The principle of operation of the densitometer is based on recording and analyzing the natural frequency of a U-shaped high-pressure capillary filled with the test medium. The placement of the capillary in a thermostat capable of maintaining its temperature to within ±0.1°C makes it possible to measure the density and study the phase behavior of aggressive media over pressure and temperature ranges of 0.1–50 MPa and 20–500°C, respectively. Measurements of the carbon dioxide density with the densitometer developed at temperature below, near, and above its critical point (31°C), as well as water density measurements at temperatures up to 375°C demonstrated good agreement with the data from the NIST (National Institute of Standards and Technology) interactive database. The density of a methanol-water mixture was measured at temperatures up to 300°C.     

A symmetry adapted approach to vibrational excitations in atomic clusters

An algebraic method especially suited to describe the strongly anharmonic vibrational spectra in molecules may be an appropriate framework to study the vibrational spectra of Na _n ⁺ clusters, where nearly flat potential energy surfaces and the appearance of close lying isomers have been reported. As an illustration we describe the model and apply it to the Be₄, H ₃ ⁺ , Be₃ and Na ₃ ⁺ clusters. Presented by A. Frank at the International Conference on “Atomic Nuclei and Metallic Clusters”, Prague, September 1–5, 1997. This work was supported in part by the European Community under contract No. CI1*-CT94-0072, DGAPA-UNAM under project IN101997 and Spanish DGCYT under project PB92-0663.     

Lattice vibrational spectra of nanocrystalline films of <Emphasis Type="Italic">para</Emphasis>-substituted benzene

We have obtained experimental low-frequency Raman spectra for para-dibromobenzene nanofilms of thickness ∼10 μm and ∼400 nm. With a decrease in the film thickness, the line frequencies are lowered, the linewidths increase, additional lines become more intense. We modeled the film structure by the molecular dynamics method and calculated the histograms of the lattice vibrational spectra by the Dean method. We found that as the film thickness decreases, the lattice parameters increase, the orientational disorder increases at its boundary. The structure of the studied film is similar to the structure of the para-dibromobenzene single crystal. In order to correctly interpret the lattice vibrational spectra, we need to take into account surface vibrations and the presence of vacancies in the structure. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 838–842, November–December, 2008.     

Dissociation and vibrational excitation of cold HD<Superscript>+</Superscript> by electron impact

We have investigated the competition between dissociative excitation, dissociative recombination and vibrational excitation processes taking place in the reactive collisions of vibrationally cold HD⁺ with electrons. The energy range 1–12 eV has been considered.     

Spectroscopic manifestations of isotope substitution in ultrasound jet-cooled complex molecules and their van der waals complexes

It is shown that, upon formation of ultrasound jet-cooled var der Waals complexes of polar molecules of 9-cyanoanthracene, 3-aminophthalimide, and 3-amino-N-methylphthalimide with water molecules, pronounced manifestations of isotope substitution in the ligand molecules take place, which manifest themselves in shifting 0–0-transitions by 5–7 cm⁻¹ and changes in frequencies of intramolecular vibrations. Spectroscopic effects of isotope substitution of atoms of the amino group are established for substituted phthalimides. We propose a new mechanism of the effect of isotope substitution on frequencies of electronic transitions which cannot be reduced to the known one (realized by means of changes in values of the zero vibrational energy) and is based instead on the change in the charge density distribution in the molecule. Belarusian State University, 4, F. Skorina Ave., Minsk 220050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 148–154, March–April, 1997.     

Quantum-chemical calculations of the structure,vibrational spectra,and torsional and inversion potentials of methylcarbamate

We present results of ab initio and DFT calculations of the structure, potential functions of the methyl group internal rotation and the amino group inversion, and vibrational frequencies and intensities in IR and Raman spectra of methylcarbamate. The calculations were carried out using different basis sets in the HF, MP2, and DFT/B3LYP approximations. The influence of both the basis set size and the allowance for electronic correlation on peculiarities of the structure of the amino group in methylcarbamate has been analyzed. It is shown that the B3LYP/6-311++G(2d, p) and B3LYP/cc-pVDZ calculations reproduce highly accurately experimental geometric parameters of methylcarbamate. Parameters of torsional and inversion potentials and characteristics of vibrational spectra calculated in different approximations show satisfactory agreement with experimental values. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 3, pp. 349–357, May–June, 2009.     

Isotope effect in the vibrational spectra of water measured in experiments with a scanning tunneling microscope

The vibrational frequencies of adsorbed H₂O and D₂O molecules are measured under high-vacuum conditions by in-cavity scanning tunneling spectroscopy. An isotope effect is observed. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 1, 37–39 (10 July 1997)