title: Infrared absorption spectrum of matrix-isolated noble-gas hydride molecules: fingerprints of specific interactions and hindered rotation.
abstract: Noble-gas hydride molecules with the general formula HNgY (Ng denotes noble-gas atom and Y denotes electronegative fragment) are usually prepared in solid noble gases. In many cases, the matrix-isolated HNgY molecules show a characteristic structure of the H-Ng stretching absorption: A close doublet as the main spectral feature and a weaker satellite at higher energy. This characteristic band structure is studied here for matrix-isolated HXeBr and HKrCl molecules. Based on the experimental and theoretical results, we suggest a model explaining the common features of the band structure of the HNgY molecules in noble-gas matrices. In this model, the main doublet bands are attributed to matrix sites where the splitting is caused by specific interactions of the embedded molecule with noble-gas matrix atoms in certain local morphology. The weaker blueshifted band is probably a fingerprint of hindered rotation (libration) of the embedded molecule in the lattice. This librational band has a mirror counterpart at lower energies appearing at higher matrix temperatures. Our present ab initio calculations for the one-to-one Xe...HXeBr complexes and the simulation of hindered rotation in a matrix support this image.
authors.affiliation: Department of Chemistry, University of Helsinki, P.O. Box 55, FIN-00014 Helsinki, Finland. Leonid.Khriachtchev@Helsinki.Fi
authors.forename: Leonid
authors.initials: L
authors.lastname: Khriachtchev
authors.forename: Antti
authors.initials: A
authors.lastname: Lignell
authors.forename: Jonas
authors.initials: J
authors.lastname: Juselius
authors.forename: Markku
authors.initials: M
authors.lastname: Räsänen
authors.forename: Elena
authors.initials: E
authors.lastname: Savchenko