Ab initio study of the electronic spectrum of C2H2+.: I.: Vertical spectrum and angular potential curves

Results of ab initio MRD-CI calculations of the vertical spectrum and trans-bending, cis-bending and torsional potential energy curves for low-lying doublet electronic states of the acetylene cation are presented. At the linear nuclear geometry these states correlate with X (2)Pi(u), 1 (2)Sigma(g)(+), 1 (2)Pi(g), 1 (2)Phi(g), 1 (2)Sigma(u)(+), and 2 (2)Pi(g), all of them being of predominantly valence character. (C) 1998 Elsevier Science B.V. All rights reserved.