LASER-INDUCED FLUORESCENCE MEASUREMENTS OF RADIATIVE LIFETIMES OF THELOW-LYING ELECTRONIC EXCITED-STATES B(0(+)) AND 2(III) OF THE BII MOLECULE

Laser-induced fluorescence of the BiI molecule in the 4160-4770 Angstr om A region was observed and band transitions of the B(0(+))-X(0(+)) a nd 2(III)-X(0(+)) systems assigned. The nature of the low-lying excite d states of BiI is discussed and measured fluorescence lifetimes used in order to establish the character of the states involved in these tr ansitions. Fluorescence lifetimes for emission from specific (v', J') rovibrational levels of the B(0(+)) (v' = 0-4) and 2(III) states have been measured for the first time by laser-induced fluorescence. The fl uorescence lifetimes for emission from the B state were in the range o f 0.25-0.5 mu s and a slight decrease in the fluorescence lifetimes wh en the vibrational energy of this molecule increases was observed and no dependence with the rotational energy was appreciated. A collision- free fluorescence radiative lifetime of tau(0) greater than or equal t o 0.6 mu s is proposed for emission from the BiI 2(III) state what has been characterized experimentally for the first time. No significant variations were found for fluorescence lifetimes of rotational transit ions within the same vibrational level of the BiI 2(III) state.