High resolution absorption spectrum of jet-cooled OCS between 64 000 and 91 000 cm−1

The absorption spectrum of jet-cooled OCS was photographed from 190 to 110 nm at a resolution limit of 0.0008 nm. No band maximum was observed between 190 and 156 nm, i.e., below 64 000 cm−1. Ab initio calculations of the electronic energies and transition moments were carried out, including spin–orbit interaction, in the frozen core approximation. Rydberg states considered have ionic core X 2Π and principal effective quantum number n*=2–5.5, electronic angular momentum l=0–5. Up to n*=3.5, l=0–2, calculations were also done in the coupled electron pair approximation. It is shown that in OCS, like in N2O, CO2 or CS2, npπ 1Σ+ states are at lower energy than npσ1,3Π. From the doublet structure shown by the corresponding transition origin bands, the rotational constant of the 4pσ1,3Π and 4pπ 3Σ− states was deduced to be B0′=0.1940(5) cm−1. Transitions involving excitation to ns or nd Rydberg orbitals, allowed in the less-symmetric molecules, were calculated to have relative intensities respectively two and ...