ROTATIONAL STATE-SPECIFIC DYNAMICS OF SIF C-2-DELTA-B-2-SIGMA(-INDUCED TRANSFER() COLLISION)

Laser excitation on the C-2 Delta-(XII)-I-2 transition was used to pre pare discrete rotational levels of the SiF C-2 Delta, v = 0 state, all owing their state-specific collisional behavior to be investigated. Ti me-and wavelength-resolved returning C-X fluorescence spectra establis hed that the initial populations were only partially perturbed by rota tionally inelastic processes within the C-2 Delta state at the typical pressures of our experiments. Transfer within the FI manifold appears to be favored by a factor of similar to 2 over transfer from F-1 to F -2. There is relatively little dependence on rotational state (in the range j = 2.5-21.5) of the rate constant for total collisional removal of the C-2 Delta state by either H-2 or N-2. AS previously establishe d, a fraction of the collisionally removed population is deposited in the lower-lying B-2 Sigma(+) state. Dispersed B-X fluorescence spectra revealed broad rotational distributions in the predominant B-2 Sigma( +), v' = 0 product level in collisions with H-2 and N-2, indicating su bstantial release of rotational energy during the transfer between ele ctronic states. There is a positive correlation between the peak and a verage product j' and the initial rotational state j. The main feature s of the observed behavior are reproduced by a limiting impulsive mode l. We believe this to be a consequence of the respective valence and R ydberg characters of the C-2 Delta and B-2 Sigma(+) states.