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An original technique is suggested for pumping a pulsed CO2 laser by a longitudinal discharge in an alternating magnetic field. A small CO2 laser with active medium ∼200 mm long, pulse energy of ∼30 mJ, and efficiency of 3.4% is designed on the basis of this technique. It is revealed that the main factor which limits the generation energy of small lasers is the development of current instabilities in a longitudinal discharge over a cross section of the discharge tube. It is noted that the growth of the instabilities accelerates as the pressure of a CO2 : N2 : H2 : He gas mixture increases to more than 0.1 atm and the specific pump power becomes higher than 3 MW/cm3. The use of an external alternating magnetic field superimposed on a pulsed longitudinal discharge makes it possible to increase the total pressure of the gas mixture in the laser to 0.4 atm when maintaining the combustion of the volume discharge. [ABSTRACT FROM AUTHOR]

The process of broadband KrCl laser λrad = 222 nm interaction with nitrogen dioxide in the atmosphere is considered. During the laser pulse, photofragmentation of NO2 occurs, followed by resonant excitation of several electronic vibrational levels of NO A2Ʃ – X2П, ν'ν''(2,2) and NO С2П – X2П, ν'ν''(0,4). The fluorescence intensity of NO A2Σ increases with increasing nitrogen pressure due to intermolecular nonradiative energy transfer from the metastable level of N2 A3Σ to the electronic level of NO A2Σ. [ABSTRACT FROM AUTHOR]

The results of experimental and theoretical studies of the operation of an electric-discharge KrCl laser (λ = 222 nm) at pump power densities of ~10 MW/cm3 are presented. The radiation energy obtained experimentally was 55 mJ for a mixture with He as a buffer gas and 120 mJ for a mixture with Ne at a pump pulse duration of ~30 ns. A numerical model of a KrCl laser using a He/Ne/Kr/HCl gas mixture with a uniform pump discharge is described. It is shown numerically that the dependence of the optimal (from the point of view of obtaining maximum radiation energy) pump power density on the partial pressures of the buffer gas and HCl is close to linear. [ABSTRACT FROM AUTHOR]

Results are presented of the experimental study of the dynamic characteristics of the laser fragmentation/laser-induced fluorescence (LF/LIF) process in nitrobenzene and para-nitrotoluene vapors under synchronized two-pulse laser irradiation. The efficiency of the LF/LIF method can be increased by several times if the time delay between the pulses of fragmentation (248.4 nm) and excitation (247.87 nm) of NO fragments is in the range 20–40 ns. [ABSTRACT FROM AUTHOR]

The process of broadband KrCl laser λrad = 222 nm interaction with nitrogen dioxide in the atmosphere is considered. During the laser pulse, photofragmentation of NO2 occurs, followed by resonant excitation of several electronic vibrational levels of NO A2Ʃ – X2П, ν'ν''(2,2) and NO С2П – X2П, ν'ν''(0,4). The fluorescence intensity of NO A2Σ increases with increasing nitrogen pressure due to intermolecular nonradiative energy transfer from the metastable level of N2 A3Σ to the electronic level of NO A2Σ. [ABSTRACT FROM AUTHOR]

Results of numerical and experimental studies on monitoring and control for optical elements of an electric discharge KrF laser by the method of density-based spatial clustering of applications with noises (DBSCAN) are presented. Different methods of processing digital signals obtained using a position-sensitive detector controlling the position of the optical axis of the laser system are considered. A numerical model of optical system stability is developed based on the DBSCAN method with an additional inclusion of digital signal processing with the use of the cumulative moving average. A technique for correction of controlled mirrors with an accuracy of 60 ± 10 µrad for their return to normal position is proposed and implemented; the alignment time does not exceed 5 min. [ABSTRACT FROM AUTHOR]

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 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]

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]

The results of remote detection of objects containing explosives with a lidar detector of traces of explosives in combination with a portable express gas chromatograph are presented. It is shown that the lidar detector of traces of explosives confidently detects the simulators of TNT, hexogen, and PETN from a distance of 5 m when sounding the surface of a sample. Laser action on the sample surface causes desorption of vapors, which are reliably detected by the gas chromatograph. It is shown that the joint use of the laser sounding and gas chromatography techniques makes it possible to increase the reliability of detection of explosives. The prospects of using the gas chromatography in the development of laser sounding techniques are determined. [ABSTRACT FROM AUTHOR]

The results are presented from experimental studies of the emission of NO radicals in a filament of femtosecond radiation produced in a N2/NO2 gas medium with total pressures of up to 1 atm. It is shown that in the recorded emission spectrum of the filament, emission transitions A2Σ+ (ν' = 0–2) – X2Π (ν'' = 0–5) of NO molecules are observed at concentrations of NO2 gas of up to 10 ppb−1. It is shown that the intensity of emission of NO A–X molecules grows along with the nitrogen pressure, due to the intermolecular nonradiative transfer of energy from the metastable level of a N2 molecule to the electron A2Σ+ level of a NO molecule. [ABSTRACT FROM AUTHOR]

Results of numerical and experimental studies of the control of optical elements of a KrF laser cavity by use of the image processing method are presented. Different methods of beam image binarization for determining the boundary dimensions and flattening the distribution of its radiation intensity are considered. Conditions allowing one to accelerate the process of dispersive cavity adjustment in the automatic regime of laser operation and to restore the initial parameters of the output beam with an accuracy of up to 5% are determined. [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]