| Diatomic sulfur molecule?S2?has analogous valence electron structure with O2,as well as the similar chemical properties.It is a very important intermediate product in combustion of sulfocompound.In addition,the observation of the B3 ?u--X 3?g- transition of S2 molecule by the Hubble Space Telescope in the stratosphere of Jupiter,perturbed by collision of the comet Shoemaker-Levy 9,illustrated the need for a comprehensive understanding the electronic structure of S2 molecule.However,the electronic structure knowledge of S2 molecule in the ultraviolet region is still too limit so far.The time-resolved and vibrational emission-resolved laser-induced fluorescence?LIF?spectra of jet-cooled supersonic S2 molecule have been studied in the range of 3040034400 cm-1,and 184 bands were observed with high(0.1 cm-1)and low(0.3 cm-1)resolutions.84 vibrational transitions were assigned to the B3 ?u--X 3?g- and B?? 3?u-X 3?g-,and the molecular constants in the excited states B3 ?u- v=0-9 and B?? 3?u v=2-12,including rotational constants,spin-orbit coupling constants,spin-rotation coupling constants,and spin-spin coupling constants,were obtained.The equilibrium molecular geometry in the vibronic ground state of B3 ?u- was determined by high-resolution spectrum.In the B3 ?u- and B?? 3?u states of S2 molecule,the vibrational level intervals,spin-spin coupling constants and spin-orbit coupling constants are anomalous variation.A lot of rotational transitions show irregular life times and selection rules.All these anomalous behaviors in the rovibrational spectrum were qualitatively explained by the homogeneous perturbations between ?-? 3 3 states.For example,the spin-spin coupling constant ? of the B3 ?u- state are negative in v'=0,2,4,6 vibronic states,and positive in v'=1,3,5 vibronic states.In addition,only the rovibronic levels which have e parity in B? 3?u state can “borrow” intensity from B3 ?u- state,and be observed experimentally through P11 and R11 rotational branches in B?? 3?u-X 3?g- transition.The corresponding Q11 rotational branches are invisible due to the need of the f parity levels.As a summary,combination of experimental rovibrational spectrum and theoretical perturbation analysis extended our knowledge about the low lying electronic states of S2 molecule. |
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