<title>Theoretical study of H-bond complexes electronic spectra</title>

Abstract

In this work were performed calculations of energy of S<SUB>0</SUB> yields S<SUB>1</SUB> vertical transition in complexes with hydrogen bonding, which can be formed in atmosphere at the interaction of molecules H<SUB>2</SUB>O with other molecules with hydrogen atom such as, for instance, HCl, being kept an danger ecological components in emissions of industrial enterprises. The equilibrium structures and molecular properties of S<SUB>0</SUB> and S<SUB>1</SUB> states of (H<SUB>2</SUB>O)<SUB>n</SUB>(HCl)<SUB>m</SUB>, n, m &lt;EQ 2, complexes were calculated at ab initio SCF, ROHF and CI levels with use of the MONSTERGAUSS program. Analysis of electron density distribution for S<SUB>0</SUB> and S<SUB>1</SUB> states was performed. The excitation energies of S<SUB>0</SUB> yields S<SUB>1</SUB> transitions (H<SUB>2</SUB>O)<SUB>n</SUB>(HCl)<SUB>m</SUB>, n, m &lt;EQ 2, complexes were determinated. The influence of hydrogen bond formation on the shift in the maximum of first absorption band of these complexes was examined. The investigations of electronic excited states of molecules allow solving some analytical problems. One of them it is a problem about identification of substances. In virtue of data about electronic excited states it is possible to carry out a study of photophysical and photochemical processes what take place after photon absorption. From an analysis of experimental data follow that formation of intermolecular hydrogen bond results in the shifts of absorption bands. The shift depends from type of electronic transition. The investigation of the nonriged molecular complexes is important for atmospheric spectroscopy purposes. Complexes of (H<SUB>2</SUB>O)<SUB>n</SUB>(HCl)<SUB>m</SUB> type are interesting from standpoints also of fundamental spectroscopy. Detailed study of structural nonrigidity effects (particularly for molecular complexes with several types of MLA) stimulates a development of new direction in molecular spectroscopy, weak bonded complexes and ensures a reception new given for the development and revision of number of positions of molecular and chemical physics, theory of reactionary ability, thermodynamics and complex formation and others.