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We report the results of experimental and numerical investigations of a discharge KrF laser with specific pump power of 3.5 and 7 MW/cm3; generation is obtained with specific radiation pulse energy of about 6 and 9.5 J/L for an internal energy efficiency of about 4%. Time dependences of the formation of charged and excited particles in a dense excimer plasma with an electron concentration of ~1016 cm–3 are obtained. The conditions for effective operation of the laser are proposed, which will ensure a further increase in the specific radiation energy by more than two times with preserved high internal laser efficiency relative to the energy input into the discharge. [ABSTRACT FROM AUTHOR]

The fluorescence of nitric oxide excited molecules NO A2Σ occurring through two-color laser action on nitrogen dioxide NO 2 has been studied. The NO 2 pre-photofragmentation stage was carried out by a 355 nm ns laser pulse to obtain vibrationally excited NO X2Π, ν ''(1) molecules. Subsequent femtosecond 472 nm laser pulse at an intensity of ∼300 GW/cm2 led to the induced fluorescence of NO A2Σ, ν ′(0) as a result of two-photon resonance absorption by the NO A2Σ–X2Π, ν ' ν '' (0,1) band. • Two-color laser action on nitrogen dioxide. • Photofragmentation of nitrogen dioxide by 355 nm laser pulse. • Detection of vibrationally excited NO X2Π, v''(1) by visible femtosecond 472 nm laser pulse. [ABSTRACT FROM AUTHOR]

Results of investigations into the development of effective N2-lasers pumped by a longitudinal discharge with specific pump powers exceeding 3 MW/cm3 are presented. It is shown that the main reason that limits the duration and energy of the output beam is unstable burning of the diffusion discharge in these modes of laser operation. Methods of forming the diffusion discharge are proposed that allow the lasing pulse duration to be increased from 5 to 20 ns. [ABSTRACT FROM AUTHOR]

This paper presents the study results of the single-frequency interaction of KrCl laser broadband radiation with nitro compound vapors in the atmosphere. The optical method of a substance spectroscopic analysis including photofragmentation of a complex R–NO 2 molecule followed by laser-induced fluorescence of vibrationally excited fragments of NO X2Π, v''>0 (PF-LIF) was studied in the experiments. It has been shown that R–NO 2 molecules exposed to λ = 222 nm FWHM 0.3 nm KrCl laser broadband radiation undergo photofragmentation followed by resonant excitation of several electronic-vibrational levels of NO X2Π, v'' (2,4). At the same time, the concentration of fragmented NO X2Π, v'' (2,4) increases due to the secondary PF-LIF NO 2 process during the nanosecond laser pulse. • Detection of nitro compounds using 222 nm laser. • Laser-induced fluorescence of NO A2Ʃ, C2Π upon fragmentation of nitro compounds. • Nonradiative energy transfer from N 2 A3Σ to NO X2Π during NO X2Π quenching. [ABSTRACT FROM AUTHOR]

The wave numbers of trans-2,3-13C2-buta-1,3-diene were calculated using a scaled quantum-chemical force field found at the MP2/6-31G*//MP2/6-31G* level of theory. The obtained results and the theoretical sets of wave numbers for twelve deutero and 13C derivatives of the trans form and five deutero and 13C derivatives of the gauche form of buta-1,3-diene found previously at the MP2/6-31G*//MP2/6-31G* level are compared with the corresponding experimental vibrational spectra corrected for the Fermi resonance. Combined analysis of the vibrational spectra of the above mentioned isotopomers was performed. [ABSTRACT FROM AUTHOR]

Quantum mechanical geometry optimizations and the calculation of vibrational frequencies of hexafluoroethane have been performed at the HF/6-31G*, MP2/6-31G*, CCSD/cc-pVDZ, and B3LYP/6-31G* levels. The force fields obtained were scaled. The necessity is stressed of carrying out the detailed analysis of the vibrational spectra of small reference molecules to determine sets of scale factors which are transferable to quantum mechanical force fields of large molecules for the purpose of predicting their vibrational spectra. [ABSTRACT FROM AUTHOR]

Stages of the scaling procedure for correcting molecular force fields obtained in rough quantum chemical calculations are discussed. The procedure includes selection of the number of scaling factors and their determination using experimental vibration frequencies of isotopomers and related molecules. It is stated that the difference in anharmonicity corrections for light molecules and their heavy analogs is to be taken into account along with possible errors in vibration frequency assignments of both isotopomers and more complex related molecules. [ABSTRACT FROM AUTHOR]

The paper presents results of experimental study of the dynamics of laser-induced fragmentation of nitrobenzene molecules. It has been shown that when two laser pulses interacting with nitrocompound molecules and their decay products (NO fragments) are time delayed, it is possible to increase the sensitivity of the method of laser fragmentation/laser-induced fluorescence by approximately an order of magnitude for an optimal time delay between the pulses. [ABSTRACT FROM AUTHOR]