Hindered rotation of HArF in solid argon: Infrared spectroscopy and a theoretical model
Anastasia V. Bochenkova, Leonid Khriachtchev, Antti Lignell, Markku R\"{a}s\"{a}nen, Hanna Lignell, Alexander A. Granovsky, and Alexander V. Nemukhin

The novel infrared spectroscopy results on the argon compound HArF in solid argon give evidence of its hindered rotation (libration). Experimental studies emphasize the thermal modification of the IR absorption bands, in particular, in the region of the previously unassigned 1992 cm$^{-1}$ absorption band. Theoretical model considers rotation of HArF inside a large fragment of argon fcc lattice with a cubooctahedral cavity for the trapped molecule. A realistic rotational potential energy surface accounting for interaction of the trapped HArF molecule with the matrix atoms is constructed, and the rotational energy levels are estimated by numerical solution of the Schr{\"o}dinger equation in the external adiabatic potential. The consistent experimental and theoretical results allow us to assign the 1992 cm$^{-1}$ absorption band to hindered rotation of HArF in solid argon.

© 2008 The American Physical Society.