THE EXCITED-STATE DYNAMICS OF THE (A)OVER-TILDE(1)B(1) STATE OF GEH2 AND GED2 RADICALS

Laser-induced fluorescence (LIF) excitation spectra of the A 1B1-X 1A1 transition of germylene radicals have been measured in a supersonic free jet. The spectra consist of progressions in the bending mode, that is, (0uplison'(2)0)-(000), upsilon'2 = 0-4 for GeH2 and upsilon'2 = 0-6 for GeD2. Rotational assignments have been made. The only lines appearing belong to the K(a)' = 0-K(a)'' = 1 sub bands, except for the (000)-(000) band of GeD2 where the (r)R0(0) line is also seen; for the higher upsilon' levels of both isotopes the bands consist of a single line, (p)P1(1). This suggests the presence of heterogeneous predissociation to Ge(3P) + H-2 in the A 1B1 state. The fluorescence lifetimes have been measured for single rovibronic levels of the A 1B1 state of both radicals. The fluorescence lifetimes of the rotational levels of the A 1B1 state decrease with increasing vibrational energy. A second predissociation channel to Ge(1D) + H-2 opens between upsilon2' = 4 of GeH2 and upsilon2' = 7 of GeD2. The heat of formation of GeH2 is estimated to be between 19053 and 19178 cm-1.