The electronic spectrum of linear and cyclic C6+.: A theoretical study

Large-scale multi-reference configuration interaction MRD-CI calculations are performed to compute the electronic spectrum of C-6(+) in its linear and cyclic conformation. The electronic spectrum of linear C-6(+) is dominated by two transitions computed at 2.57 eV ((2)Pi(g) <-- X (2)Π(u)) and at 5.80 eV (3 (2)Π(g) <-- X (2)Pi(u)). The first dipole-allowed transition of cyclic C-6(+) is calculated at 0.58 eV ( B-2(2) <-- X (2)A(1)) and this transition should help to identify cyclic C-6(+) since there are no transitions of linear C-6(+) in this energy region.