A NEW LOW-LYING POTENTIAL-ENERGY SURFACE FOR SIH(2+)

High-resolution laser photofragmentation spectroscopic studies of SiH2+ have stimulated interest in the low-lying potential energy surfaces of the system. Diatomics-in-molecules, CAS-SCF and multireference Cl studies have confirmed the existence of a previously unexplored low-lying potential energy surface which is likely to play an important role in the predissociation dynamics of the system. At slightly stretched Si-H separations the new surface is found to participate in a conical intersection with the ground electronic state of the molecular ion and itself becomes, or correlates with, the ground state of the system in these geometries.