Low-lying stationary states of Si3H and its anion

The ground states of Si3H and Si3H− have been found as 2A1 (C2v) and 1A1 (C2v), respectively, and both correspond to planar cyclic hydrogen-bridged geometries. The adiabatic electron affinity is calculated as 256 kJ/mol at the CCSD-(T) level of theory. The in-plane fluxionality of the neutral radical is much more pronounced than that of the negative ion. Besides these two minima, various stationary points (minima as well as transition states) for the neutral as well as the negative ion have been located. Several triplet negative ion states are found to be adiabatically stable.