The fundamental C–H stretching vibration and associated intermolecular bending hot band of SCO–HCN
Infrared optothermal laser spectroscopy has been used to study the linear SCO–HCN complex. The observed spectrum corresponds to excitation of the C–H stretching vibration out of either the ground state or v=1 of the lowest frequency intermolecular bending state. A b i n i t i o calculations have also been carried out for this system which give, at least for some properties, results which are in good agreement with experiment. A comparison between the SCO–HCN results and those of the linear CO2–HCN complex studied previously, reveals that the shifts in the C–H vibrational frequency upon complex formation are rather similar. This is despite the fact that OCS and CO2 have very different point multipoles, suggesting that the electrostatic part of the interactions are likewise different for these two partners. Nevertheless, a distributed multipole calculation shows that, at the intermolecular separations characteristic of these complexes, the electrostaticinteractions are in fact quite similar at the oxygen ends of OCS and CO2, providing an explanation for the similarity between the frequency shifts of these two complexes.