Stability and structure of the C2H6+ion: investigation of the photoelectron spectrum of ethane below 14 eV usingab initiomethods

Abstract

Potential surfaces have been calculated for ethane and the three lowest-lying states of its positive ion using ab initio SCF and CI methods. The C2H6 + states treated consist of two 2 Ag and a single 2 Bg species in the lowest nuclear symmetry considered (C 2h ) and they are found to possess markedly different equilibrium structures both compared to ethane itself and also to one another. The C2H6 + ground state (2 Ag ) is a pure 2 A 1g species (D 3d symmetry) at large CC distances with optimum CCH angles of 100°, but at shorter R CC values it becomes a mixture of both 2 A 1g and 2 Eg character through a large diborane-type (v 12) distortion. The second 2 Ag species is complementary to the first and appears to prefer D 3d symmetry both at large CC values, for which it is a 2 Eg species, and also at short distances, for which it eventually becomes a 2 A 1g state. The 2 Bg species correlates with 2 Eg in D 3d symmetry but is Jahn-Teller distorted, possessing an R CC value of 2·75 bohr and an HCH angle of onl...