Theoretical study of the potential energy surfaces and bound states of HCP

Global, ab initio potential energy surfaces for HCP in its ground 1 (1)Sigm a(+) (1 (1)A') and low-lying excited 1 (1)A ", 2 (1)A', and 1 (1)Delta(2 (1 )A ") electronic states are determined. The multireference configuration in teraction method at the double zeta with polarization basis set level is us ed, although some calculations augmented with diffuse functions are also di scussed. Numerous quantum mechanical rovibrational states are then obtained for these surfaces, with emphasis on those corresponding to excited electr onic state levels which have not been studied theoretically before. The res ults agree reasonably well with available experimental data for the 1 (1)A " state. Furthermore, the presence of certain local minima on the 1 (1)A " and 2 (1)A' surfaces leads to one new series of levels on the 1 (1)A " surf ace, and two new series on the 2 (1)A' surface. (C) 2000 American Institute of Physics. [S0021-9606(00)30413-5].