Pressure dependences of intensities and decay rates of time-resolved luminescence of acetophenone, benzophenone, anthraquinone were used to obtain the efficiencies of vibrational and triplet-triplet energy transfer. It was shown that vibrational relaxation of the chosen molecules can be interpreted in terms of two consecutive processes: rapid collisional relaxation of molecules from initially prepared states to a vibrational distribution at Tvib by vibration-vibration process and relaxation of this vibrational distribution to the thermal one (vibration-translation process). At relatively small internal eneigy < 10000 cm -", the collisional efficiencies of the vibration-vibration process in mixtures with polyatomic bath gases had values typical of processes with a supercollision contribution. Molecules relaxed from the upper vibrational level to the vibrational distribution after several collisions (2-3). The average energies transferred per collision are well correlated with predictions of the simple ergodic theory of collisional energy transfer. The majority of the collisions took part only in vibration-translation energy transfer of relatively small energies. The efficiencies of triplet-triplet energy transfer were analyzed for acetophenone, benzophenone and anthraquinone as donors and biacetyl-acceptor in a gas phase when energy of about 20000 cm' was transferred. It permitted us to elucidate the common features of highly energetic collisions. It was shown that the efficiencies are much lower than the gas kinetic ones and depended on the vibrational energy and temperature. It was discussed how to enhance triplet-triplet efficiencies due to vibrational excitation of a donor molecule.

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h t i t u t e of Molecular and Atom2 Physics, Academy of Sciences of Belarccs, 220071, Minsk, Belarus ._______-_.___-__--___ ABSTRACT Collisional relaxation was probed by CO, laser activated delayed fluorescence. The experimental information was adopted to determine the average energies transferred per collision {M) from highly vibrationally excited polyatornic molecules to parent collider. The values of @E) decreased with increasing the number of atoms in the excited molecules in line: biacet9, acetophenone, benwphenone, antraquinone. The dependences of (M) on the number of factors such as: I ) the average vibrational energy residing in the vibrational modes of excited molecules; 2) the potential of intermolecular interaction; 3) the reduced mass, and others were analyzed in details. The general interplay was noticed between (M) and the molecular parameters which determined the increasing interaction strength and the decreasing energy transfer efficiency due to the adiabatic constraints on the energy transfer.

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The photoacoustic gas analyser ulilizthg an indUSIIiaI CO2 wave-guide laser was presented to quantitatively determine low conceniralion ofgaseous pollutants in real air. The PA resonant H-type cell design was described. By analysing the dependence ofthe PA signal on a modulation frequency, the most suitable acoustic resonance was chosen for practical use. The specirophone characteristic constantA was determined for various CO2 laser lines which coincided with air pollutants absorplion lines. The schematic diagram ofthe full-automalic PA gas analyser was considered, and the interconnection of its units was outhned. It is shown that PA gas analyser concentration characteristic is linear in a wide concentration range overlapping three orders of magnitude; pollutants detection threshold values are considerably less than their utmost admissible concentrations in air ofthe living zone. An idea ofusing Starks modulalion at atmospheric gas pressure analysis is examined.