Accurate spectroscopic calculations of the 17 Λ-S and 59 Ω states of the AsP molecule including the spin-orbit coupling effect.

The potential energy curves (PECs) of 59 Ω states generated from the 17 Λ-S states (X(1)Σ(+), a(3)Σ(+), 1(5)Σ(+), b(3)Δ, c(3)Π, 1(5)Π, 2(5)Σ(+), 2(3)Δ, 2(3)Π, 3(3)Σ(+), A(1)Π, 2(3)Σ(+), 3(5)Σ(+), 1(7)Σ(+), 1(5)Δ, 2(5)Δ, and 2(5)Π) of AsP molecule are studied for the first time for internuclear separations from about 0.10 to 1.10nm. All the Λ-S states are contributed to the first three dissociation channels of AsP molecule except for the A(1)Π. The 2(3)Σ(+), 3(5)Σ(+), 1(7)Σ(+), 1(5)Δ, 2(5)Δ, and 2(5)Π are found to be the repulsive states. The a(3)Σ(+), 1(5)Π, b(3)Δ, 1(7)Σ(+), 1(5)Δ, 2(5)Δ, and 2(5)Π are found to be the inverted states. Each of the 3(3)Σ(+), c(3)Π, 2(3)Π, 1(5)Π, and 1(5)Σ(+) states has one potential barrier. The PECs are calculated by the CASSCF method, which is followed by the internally contracted MRCI approach with Davidson correction. Core-valence correlation and scalar relativistic corrections are included. The convergent behavior of present calculations is discussed with respect to the basis set and level of theory. The spin-orbit coupling effect is accounted for. All these PECs are extrapolated to the complete basis set limit. The spectroscopic parameters are evaluated for the bound states involved, and are compared with available measurements. Excellent agreement has been found between the present results and the measurements. It shows that the spectroscopic parameters reported in this paper can be expected to be reliably predicted ones. The conclusion is gained that the effect of spin-orbit coupling on the spectroscopic parameters is not obvious for all the Λ-S bound states except for few ones such as 1(5)Σ(+) and c(3)Π.