LIFETIME MEASUREMENTS OF SELECTIVELY EXCITED ROVIBRATIONAL LEVELS OF THE V B-1(2) STATE OF CS2

The radiative lifetimes of selectively excited rovibrational levels of the V B-1(2) state of the CS2 molecule have been measured under colli sion-free conditions in a cold molecular beam using a pulse-modulated frequency-doubled single-mode cw dye laser. Pure exponential fluoresce nce decays ware found for all excited levels. The lifetimes, scatterin g considerably in the range of 2-13 mu s, give evidence of interaction s of the V B-1(2) state with background states. A deperturbation analy sis performed for rotational levels involved in local two-level intera ctions yields detailed quantitative information on the V B-1(2) state and on the background levels. It is shown that these levels represent rovibrational levels of the B-2((3)A(2)) state and highly excited rovi brational levels of the X (1) Sigma(g)(+) electronic ground state. The coupling mechanisms are: (1) the spin-orbit interaction between the V B-1(2) state and the B-2((3)A(2)) state where the latter is coupled t o the X 1 Sigma+g ground state by spin-orbit/vibronic and spin-orbit/C oriolis interaction and (2) the Coriolis coupling of the V B-1(2) stat e to the X (1) Sigma(g)(+) ground state. Further sources of perturbati ons are the spin-uncoupling in the (3)A(2) state and the Renner-Teller coupling of the V B-1(2) state to the (1)A(2) state. From the measure d radiative lifetimes of the background states information on the elec tronic structure of the CS2 molecule is gained. (C) 1996 American Inst itute of Physics.