INFRARED SPECTRUM OF THE CS$_2$ TETRAMER: OBSERVATION OF A STRUCTURE WITH $D_{2d}$ SYMMETRY

Abstract

Infrared spectra of carbon disulphide clusters are studied in the region of the CS$_2$ $\nu_3$ fundamental band ($\sim$1535 cm$^{-1}$), using a tuneable diode laser to probe a pulsed supersonic slit jet expansion. A symmetric rotor parallel band at 1551.438 cm$^{-1}$ is assigned to CS$_2$ tetramer. The likely structure is a staggered and tilted barrel with $D_{2d}$ symmetry, similar to the previously observed oblate tetramer of nitrous oxide, in reasonable agreement with that calculated from an empirical CS$_2$ intermolecular potential function. This is the first high-resolution spectroscopic detection of CS$_2$ tetramer, and the calculations suggest that there could be other lower energy isomers of (CS$_2$)$_4$ which are not yet observed.