Theoretical and experimental study on small molecular ions. I.Ab Initio calculations on CSe, CSe+, and HCSe+ species

Abstract

Ab initio molecular-orbital calculations were carried out on carbon monoselenide (CSe), its cation CSe+, and the selenoformyl cation HCSe+. Equilibrium- and transition-state geometries on the potential energy surfaces (PES) were located at the HF and MP2 levels using a valence double-ζ (d, p) basis set on H and C and the Huzinaga valence triple-ζ (d) basis set on selenium, respectively. The global minimum on the HCSe+ (PES) is the linear species 3 with the dissociation energy towards H and CSe+ of 151.5 kcal mol−1 (MP4//MP2 + ZPE level). While at the HF level the strongly bent isomer 4 is a local minimum structure lying 67.8 kcal mol−1 above 3 and separated from 3 by a small barrier of 6.2 kcal mol−1, MP2 geometry optimizations suggest that CSeH+ isomer is unstable.