Ground and excited state properties of ThB- and ThB: a theoretical study.

In the present work, we studied a series of electronic and spin-orbit states of ThB- and ThB using high-level multireference and coupled-cluster theories. We report the potential energy curves (PECs), equilibrium electron configurations, spectroscopic constants, energetics, and spin-orbit coupling effects of 17 and 19 electronic states of ThB- and ThB, respectively. The ground state of ThB- is a single-reference 13Π with a 1σ22σ23σ11π3 electron configuration. Detachment of an electron from the doubly occupied 1π orbital of ThB-(13Π) produces the single-reference ground electronic state of ThB (14Σ-). The ground spin-orbit states of ThB- and of ThB are 13Π+0 and 14Σ-3/2, respectively. The vertical electron detachment energy (VDE) of ThB- and the adiabatic electron attachment energy (AEA) of ThB at our largest CBS-C-CCSD(T)+δT(Q)+δSO (complete basis set effect, spin-orbit effect, and triple and perturbative quadruple electron correlation effect added coupled-cluster theory with single, double, and perturbative triple excitations) level are 1.473 eV and 1.459, respectively. The reaction of Th(3F) + B(2Po) produces the ground state of ThB with a bond energy of 2.843 eV. Finally, we estimated a heat of formation, ΔH0f (298 K), of 891.01 kJ mol-1 for the ThB molecule. The high-level findings of this work are expected to aid and motivate future experimental spectroscopic investigations of ThB and ThB- species.