Alternation of the spin–orbit coupling in the ²Π ground state of HC_nS (n = 1–12) radicals

Abstract

First-order calculations of spin–orbit constants, dipole moments and carbon–sulphur distances have been performed for HC _n S (n = 1–12) radicals in the ²Π electronic ground state. It is found that these molecular properties alternate with even or odd numbers of carbon atoms in the chains and the spin–orbit constant A _SO is around −300 cm⁻¹ for n even and about +120 cm⁻¹ for n odd throughout the series. This agrees with the experimentally determined value of about −270 cm⁻¹ for HC₂S, but the theoretically predicted A _SO values are much larger than the values given for HC₃S and HC₄S from a fit of their millimeter-wave spectra. Values that were too low were also assumed in the analysis of the rotational spectra of n = 4–8.

Keywords:

• spin-orbit coupling
• HC _n S radicals

Acknowledgement

The work performed in Basel was supported by the Swiss National Science Foundation (project 200020-124349/1).