Electronic states and potential energy surfaces of YH 2

Abstract

Three low-lying electronic states of YH 2 namely, 2A 1, 2B 1 and 2A 2 have been studied using the complete active space SCF method (CAS SCF) followed by configuration interaction calculations. Relativistic effective core potentials have been employed for the Y atom. Bending potential energy surfaces for the 2A 1, 2B 1 and 2A 2 are also obtained. The ground state of YH 2 is found to be the 2A 1 state with a bent geometry (θ e = 123°, r e = 1.94Å). This equilibrium structure is nearly 9 kcal/mol more stable than the linear YH 2 ( 2Σ g +) state while the bent 2B 1 and 2A 2 states are about 3 kcal/mol lower in energy in comparison to their linear counterparts. The barrier for the insertion of Y atom into H 2 is found to be low for the 2A 1 state (< 23 kcal/mol) but significantly higher for the 2B 1 and 2A 2 states.