Rovibronic Spectrum of PbS in 19520-22900 cm^-1

The rovibronic spectrum of PbS in the range of 19520 -22900 cm ^\bf-1 are investigated using the laser ablation-laser induced fluorescence method. The spectra in this range are assigned as the transitions of A-X and B-X according to the spectral analyzation. The upper electronic state of the transition in the range of 19520-22900 cm ^\bf-1 is analyzed and discussed, and it is concluded that the upper state, A , is a mixture of ^3 \Pi_0^+ and ^3 \Sigma_0^+^-states, the ^3 \Pi_0^+ state is in domination. The spectrum in the range of 22025 -22900 cm ^\bf-1 is assigned as the B^3 \Pi_1-X^1 \Sigma^+ transition. The molecular constants of these two transitions are derived from the observed spectra. The Frank-Condon factors (FCFs) of these two transitions are also calculated using the RKR/LEVEL method. All the results are compared with the reported theoretical and experimental results, showing that the A state is a mixing state which is in consistent with Balasubramanian's relativistic configuration interaction calculation result. And our calculated FCFs are in agreement with our recorded spectra.