The electronic structures of the X2Σ%2B, A2Π, B2Σ%2B, 32Σ%2B, and 22Π states of LiCl- anion are performed at MRCI%2BQ level. Davison correction, core-valence correction and spin-orbit coupling effect are also considered. The ground state X2Σ%2B of LiCl- anion correlates with the lowest dissociation channel Li(2Sg) %2B Cl-(1Sg), the A2Π and B2Σ%2B states correlate with the second dissociation channel Li(2Pu) %2B Cl-(1Sg), the 32Σ%2B and 22Π states correlates with the third dissociation channel Li-(1Sg) %2B Cl-(2Pu).
Spectroscopic parameters are calculated by solving the radial Schr?edinger equation. The equilibrium internuclear distance Re of the ground state X2Σ%2B is 2.1352 A, which is a little bigger than the experimental data, the error is 0.5%. It is a depth potential well, the dissociation energies De is 1.886 eV. The values are in a good agreement with experimental data. The A2Π state is placed at 13431.93 cm-1 above the X2Σ%2B state. Re is 2.1198 A, which is only 0.0154 A smaller than that of the X2Σ%2B state. The energy levels Gv and rotational constant Bv of five L-S states are also calculated. The values are in a good agreement with available theoretical ones. The electronic structures of the excited states are also reported. the SOC effects are weakly influenced on the spectroscopic parameters for the X2Σ1/2%2B, A2Π1/2, A2Π3/2, and B2Σ1/2%2B states. From the analysis of the SO matrix, it can be seen that the SOC effect plays a little role for the A2Π-X2Σ%2B transition, and it can be ignored.
The scheme of laser cooling of LiCl- anion has constructed at spin – free level. The A2Π-X2Σ%2B transition has a highly diagonally distributed Franck-Condon factor f00 = 0.9898, the calculated branching ratios of the diagonal term R00 is 0.9893, and spontaneous radiative lifetime of A2Π is 35.45 ns. A main pump laser and two repumping lasers driving the A2Π-X2Σ%2B transitions are required. The laser wavelengths are 744.10 nm, 774.30 nm, and 772.42 nm, respectively. Due to the summation of R00, R01, and R02 is closer to 1, the A2Π-X2Σ%2B transition is a quasicycling transition. These results imply that the LiCl- anion is a candidate for laser cooling.
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