HX, N2double doping experiments in monatomic matrices: Near infrared spectra and symmetry properties of the intermolecular potential

摘要

The infrared spectra of monomeric and dimeric hydrogen halides trapped in mixed nitrogenhyphen;rare gas matrices are recorded for various nitrogenndash;rare gas ratios. The analysis of the displacement of the monomer and dimer band frequencies strongly suggests the formation of HXndash;nN2aggregates inside the monatomic crystal when varying this ratio from pure rare gas to pure nitrogen. A convenient analytical form is proposed in order to describe the interaction potential energy between the foreign molecules and the matrix. Numerical procedures based on realistic but tractable models for the representation of the doped crystal structure are then used in order to calculate the conformation of some aggregates inside the crystal and to prove the strong tendency for foreign molecules to agglomerate each other. We can thus explain the behavior of the HX monomer and dimer bands frequencies that decrease when doping with N2molecules down to a minimum for a N2ndash;rare gas ratio 60percnt;ndash;70percnt; and then increase up to the HXndash;pure nitrogen frequencies, in terms of a symmetrization process in the conformation of the aggregates around the HX lsqb;or (HX)2rsqb; molecule.