Vibrational spectra of OC⋯HCl complex in Kr solutions at liquid to solid phase transition

Abstract

Fundamental and first overtone bands of HCl, CO molecules and OC⋯HCl complex were studied in liquid and solid Kr solution near the phase transition. Triplet to doublet shape transformations were observed for both fundamental ν(HCl) and first overtone 2ν(HCl) bands at liquid to crystal state transition. Self-association processes of HCl in Kr solutions have resulted in the registration of two to several new sharp peaks on the low frequency P branch of the ν(HCl) band, whereas they only gave an additional diffuse absorption on the P branch of the 2ν(HCl) band. Evolution of the ν(CO) and 2ν(CO) bands, observed at temperature lowering of liquid Kr solution, has shown an increased restriction of the rotational motion of CO in an orienting field of the nearest neighbors. Triplet to singlet shape transformation was found for both the CO bands at liquid to crystal state transition. Asymmetry of the central parts of the bands and high frequency shoulder, which are increased at temperature lowering of the solids, suggest the consecutive transformation of orientational motion of CO into libration and growth of vibrational–translational coupling in CO doped low temperature Kr crystal. OC⋯HCl complex formation with a weak intermolecular H-bond were studied by observation of the red shifted νc(HCl) band and of the blue shifted νc(CO) and 2νc(CO) sharp bands in the solid state. Spectral parameters of dimer bands were estimated.