Accurate spectroscopic properties of 19 low-lying states of PCl radical including the electronic transition properties.

The spectroscopic properties are in detail studied for the 1(1)Σ(-), 2(1)Σ(-), b(1)Σ(+), c(1)Π, 2(1)Π, 3(1)Π, a(1)Δ, 2(1)Δ, X(3)Σ(-), C(3)Σ(-), 3(3)Σ(-), 1(3)Σ(+), A(3)Π, B(3)Π, 3(3)Π, 1(3)Δ, 2(3)Δ, 1(5)Σ(-) and 1(5)Π states, which are yielded from the first two dissociation limits, P((4)Su)+Cl((2)Pu) and P((2)Du)+Cl((2)Pu), of the PCl radical. Of the nineteen states, the 3(3)Σ(-), 1(3)Σ(+), 1(3)Δ, 2(3)Δ and 1(5)Π states are the repulsive ones. The 2(1)Σ(-), 2(1)Δ and 1(5)Σ(-) states and the second well of A(3)Π state are very weakly-bound ones. The A(3)Π and B(3)Π states, the B(3)Π and 3(3)Π states, and the 2(1)Π and 3(1)Π states have the avoided crossings. The A(3)Π state is found to possess the double well. The potential energy curves (PECs) are calculated with the CASSCF method followed by the internally contracted MRCI approach with Davidson correction together with the Dunning's correlation-consistent basis sets, aug-cc-pV6Z. To improve the quality of PECs, core-valence correlation and scalar relativistic correction calculations are included simultaneously. The PECs are extrapolated to the complete basis set limit. The vibrational properties are evaluated for several weakly-bound states. The spectroscopic parameters are determined, and compared with those available in the literature. The Franck-Condon factors and radiative lifetimes of the transitions from the A(3)Π, B(3)Π and 3(3)Π states to the X(3)Σ(-) state and from the c(1)Π, 2(1)Π and 3(1)Π states to the a(1)Δ state are calculated for several low vibrational states. And some necessary discussion is performed. Analyses demonstrate that the spectroscopic properties of PCl radical reported in this paper can be expected to be reliably predicted ones.