The results of preliminary studies narrowband scattering of laser radiation with a wavelength of 532 nm of the complex system of "airgel - water", depending on the water content in airgel nanopores are presented. In order to study the scattering in nanoporous media broadband radiation two versions of photoacoustic calorimeter are tested.
Mechanisms of nonlinear absorption and ionization of pure atomic argon and molecular nitrogen gases by UV femtosecond
laser pulses were studied using photogalvanic and photoacoustic techniques. The effect of the intermediate Rydberg
resonance, its dynamic Stark perturbation and ponderomotive upshift of the first ionization potential of argon
atoms and nitrogen molecules by the intense laser pulses has been revealed by observing an increase of a power slope of
ion yield from three to four at increasing laser intensity.
The method of time-resolved photoacoustic spectroscopy is applied to study the weak aerosol absorption of shortwave radiation in the atmospheric air. Using synchronous measurements of aerosol light absorption coefficients by a pulsed photoacoustic spectrometer and mass concentration of black carbon by an Aethalometer, we determine the values of the efficiency of aerosol light absorption in the atmospheric air in the shortwave spectral range for three wavelengths: (0.532 µm)=(5.49±3.57)m2 g–1, (0.694 µm)=(4.46±2.61)m2 g–1, and (1.064 µm)=(2.87±1.84)m2 g–1. The experimental results are approximated by the spectral dependence ()=3.1–0.92, where wavelength is expressed in micrometers. We discuss the calibration procedure for the pulsed photoacoustic spectrometer in studying the aerosol absorption.
The vibrational translational relaxation time of 001 state of ozone in binary mixtures with noble gases (He, Ne, Ar, Kr, Xe) was measured from the phase shift of the photoacoustic signal relative to the amplitude-modulated radiation of the CO2 laser used for excitation of O3. A three-level kinetic model of O3 is used to fit the experimental and calculational data of the phase shift and to determine the vibrational relaxation rate coefficient. The vibrational relaxation rate constants for 001 state were obtained corresponding to the deexcitation by the direct way of the 000 state and in two steps through the 010 state. Dependences of the relaxation rate constants on molecular mass and polarizability of buffer gas are presented. Estimates of vibrational relaxation rate constants in the Landau-Teller approximation for various molecular masses and polarizabilities of buffer gas were performed.
New technique for measurement of the water vapor absorption coefficient for pulse UV radiation is described. This technique allows the useful signal caused by gas absorption to be separated from the signal caused by absorption by walls and windows of the cell. Both the photoacoustic and photoionization signals are observed in the cell by the action of radiation at the wavelength 266 nm upon water vapor and its binary mixtures with the other gases.
Characteristic properties of forming of the photoacoustic detector signal at excitation of absorbing gas molecules by a short laser pulse ((tau) << (tau) vt) allowing for the natural oscillations of microphone membrane are considered. The technique for (tau) vt measurement is proposed on the strength that the signal form is determined by the oscillation mentioned above under low pressure (P <EQ 10 torr). the results of measurement of (tau) vt of the vibrational state (nu) 1 + 3 (nu) 3 in H2O for the collisions H2O- H2O and H2O-air are presented.
The values of broadening and shift coefficients induced by H2 pressure for the H2O absorption line centered at 694.38 nm (414-515 transition of 000-103 band) were measured. A nonlinear character of the H2O absorption line center shift dependence on H2 pressure at its increase beyond 450-500 Torr was experimentally revealed.
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