The singlet–triplet splittings in AsH+2, SbH+2, and BiH+2 and bond energies and ionization potentials of AsH2

Abstract

The three low-lying electronic states (1A1, 3B1, 1B1) and their five spin–orbit states of AsH+2, SbH+2, and BiH+2 are investigated using complete active space MCSCF/second-order configuration interaction/relativistic CI schemes (CASSCF/SOCI/RCI). In addition the X 2B1 ground state and the excited 2A1 state of AsH2 and the X 3Σ− state of AsH are studied at the same levels of theory. The CASSCF/SOCI calculations yield De (HAs–H)=69.1 kcal/mol and De (AsH)=62.4 kcal/mol in excellent agreement with experimental values of D0(HAs–H)=66.5 kcal/mol and D0(As–H)=64.6 kcal/mol obtained by Berkowitz recently. The adiabatic CASSCF/SOCI ionization potential of the X 2B1 state of AsH2 to form the X 1A1 state of AsH+2 is 9.25 eV in comparison to an experimental value of 9.44 eV obtained by Berkowitz and Cho. The X 1A1–3B1 separations of AsH+2, SbH+2, and BiH+2 are calculated as 22, 31, and 35 kcal/mol, respectively. All the three ions were found to have bent equilibrium structures. The spin–orbit effects are found to be very significant for both BiH+2 and SbH+2, which changed the bond angle of 3B1(A1) to a considerable extent by contamination with 1A1. The relativistic density matrices and dipole moments are also obtained for all the species from the RCI wave functions.