The Study On Rovibronic Spectra Of PbS A-X And B-X Transitions

Diatomic molecular spectroscopy plays an important role in identifying molecules,obtaining their structures and energy levels.At the same time,the research results of the development of molecular spectroscopy are becoming increasingly important in other fields.As important semiconductor materials,PbS have been widely used in information,industry and other fields.By studying the spectrum of PbS molecule,the information such as spectral constants,potential energy curves of electronic states and transitions probabilities between energy levels of PbS molecule can be obtained.These information can be helpful for the research and application of PbS in materials and other fields.In this article,the rovibronic spectra of PbS molecule in the range of 19 520-22900 cm^-1 were studied.In the experiment,firstly,Pb plasma was obtained by laser ablation,and then it reacted with H₂S to generate PbS molecule.Secondly,the fluorescence signals between A-X and B-X electronic states of PbS were detected by laser-induced fluorescence technology.After signal processing,the rovibronic transition spectra were obtained.Based on the experimental data in this paper,we obtained the following information of PbS molecule:First,the spectrum in the range 19 520-21 090 cm^-1 was assigned as the A-X transition,and the upper state A of the A-X transition was discussed.It was the first time that the upper state A of PbS was proved to be not a singlet state,but rather a mixture of ~3Π₀+and ~3Σ^-₀₊states,and the ~3Π₀+state is in domination.This conclusion was different from Greenwood and Barrow’s conclusion that the A state of PbS is a singlet state.At the same time,the molecular constants of the A state were given and the spectral lines of A-X transition were calibrated by analyzing the spectral data obtained from the measurements.Second,the spectrum in the range of 22 025-22900 cm^-1 was assigned as the B-X transition,the upper state B is ~3Π₁.Meanwhile,the molecular constants of the B state were derived by analyzing the corresponding spectral data,and the corresponding spectral lines were calibrated.Finally,the spectral information of PbS measured in this paper was all analyzed and discussed,and compared with theoretical and experimental results in the references.Furthermore,the A-X and B-X transitions of PbS were studied in theoretical calculation.Specific work as follows:1)the potential energy curves（PECs）of A,B and X states of PbS molecule were calculated and analyzed by RKR program.2)the Franck-Condon factors of A-X and B-X transitions were calculated by LEVEL program,that is,the transition probabilities between the vibrational energy levels of A-X and B-X transitions,and compared with the experimental results obtained in this paper.