ON THE PERTURBATION OF THE (B) OVER-TILDE2A' STATE OF HCO BY THE 1-4A'' AND 1-4A' STATES - SURFACES OF INTERSECTION AND SPIN-ORBIT INTERACTIONS

The excited B 2A' state of HCO is studied using multiconfiguration self-consistent field/configuration interaction wave functions of 300 000 to 1 400 000 terms. Equilibrium structures for the X 2A', B 2A', 1 4A'', and 1 4A' states are determined as is the X 2A' - B 2A' electronic transition dipole moment. This dipole transition moment vector is found to make an angle of approximately + 34-degrees with the inertial a axis of the B 2A' state. The possibility of spin-orbit induced perturbation of the low-lying vibrational levels of the B 2A' state attributable to the 1 4A'' or 1 4A' states is considered. The minimum energy points on the surface of intersection of the B 2A' and 1 4A'' states, denoted MECP(B 2A' - 1 4A''), and of the B 2A' and 1 4A' states, denoted MECP (B 2A' - 1 4A'), are determined. MECP (B 2A' - 1 4A'') is located very close to the 1 4A'' equilibrium structure and is only approximately 1500 cm-1 above the B 2A' minimum. At MECP (B 2A' -1 4A'') the parallel and perpendicular components of the B 2A' approximately 1 4A'' spin-orbit coupling, based on the microscopic Breit-Pauli operator, are approximately 50 and 4 cm-1, respectively. No barrier was found separating the B 2A' equilibrium structure and MECP(B 2A' - 4A''). MECP(B 2A - 1 4A') is close to the 1 4A' minimum and is placed approximately 2400 cm-1 above the minimum of the B 2A' state. However, the B 2A'approximately 1 4A' spin-orbit interaction, a perpendicular interaction, is only approximately 1 cm-1. Additional points on the B 2A' - 1 4A'' surface of intersection and the corresponding B 2A' approximately 1 4A'' spin-orbit interactions are determined.