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Study of the vibrational energy redistribution in highly-excited molecules both in gas phase and on surfaces

The peculiarities of intra- and intermolecular vibrational relaxation in collisions of highly excited small polyatomic molecules was studied by time-resolved Raman probing technique. The strong influence of intramolecular interactions on the rate and pathways of relaxation was found for the molecules excited into pre-chaotic energy domain. This interaction causes "collisionally-induced IVR" that results in extremely fast (about single gas kinetic collision) energy redistribution from optically excited "bright" states to nearby "dark" ones. The theoretical model of above process was developed.
The desorption process of organic and bio-organic molecules from frozen liquid matrix by pulsed IR laser radiation was studied with the use of RETOF MS combined with REMPI techniques. It was shown that an evaporation of large thermally unstable molecules can be realised without decomposition under appropriate irradiation conditions. The detection limit of about 1 ppt level of organic molecules in water was realised. It was shown that fast roto-vibrational relaxation provides significant cooling of analyte molecules in collisions with matrix molecules preventing its decomposition.
Physico-chemical processes initiated by 5mkm IR MPD of transition metal carbonyls were studied by time-resolved fluorescence spectroscopy. A free metal atom production by the collisionless 5 mkm IR MPD of M(CO)6 (M = Cr, Mo) with a second harmonic of a TEA CO2 laser was observed for the first time. The metal atoms in the ground state were detected by the UV laser induced fluorescence technique. The production of naked metal atoms was explained by a sequence of IR MPD processes of parent molecules and vibrationally excited photofragments M (CO)x (x¡6). Broad structureless transient UV-visible emission extending from 250 to 750 nm region was observed for the first time when low pressure mixes of M(CO)6 (M = Cr, Mo and W) and O2 molecules were irradiated by a 5 mkm laser pulse which was explained by the IR MPD of parent species and bimolecular reactions of the resulting highly unsaturated transition metal carbonyls with oxygen.

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