Talk

Speaker:

Alexey V. Baklanov

Institute of Chemical Kinetics and Combustion, Novosibirsk, Russia

Title:

Supremolecular Photophysics and Photochemistry of van der Waals Complexes of Molecular Oxyge X-02

Abstract:

Optical transitions in molecular oxygen are strictly forbidden by spin and/or orbital symmetry within spectral range from IR to the very important UV region. The enhancement of photoabsorption in molecular oxygen O2 induced by intermolecular interaction in the gas and condensed phase is a well-known phenomenon. The enhancement factors can be of many orders of magnitude depending on interaction partner X. This explains the interest to the nature of this enhancement and to the "enhanced" photochemistry of oxygen in molecular environment which are the subject matter of presented work. The van der Waals (vdW) complex of molecular oxygen X-O2 is an adequate and experimentally convenient model for the study of these phenomena. To assign the nature of the electronic states involved, to identify generated reactive species and mechanism of their formation the UV-initiated photo processes in van der Waals complexes X-O2 have been investigated. The techniques of velocity map imaging of the photofragments, the REMPI−TOF-MS and spectroscopy of "collisional" complexes as well as ab initio calculations have been applied. The results obtained in collaboration of Novosibirsk and Nijmegen groups reveal "dramatic" change in the mechanism of photodissociation of oxygen in vdW complex X-O2 as compared with the free O2 molecule and clearly indicate supramolecular nature of the photoabsorption and photodissociation of oxygen in the molecular environment. Particular attention is paid to the revealed channel of supramolecular photogeneration of singlet oxygen which is very important reactive state of oxygen. Implementation of the new approach for measurements of binding energy in weakly bound molecular complexes is also considered.