Journal of Physical Chemistry A, Vol.102, No.1, 51-59, 1998
Rotational state-specific dynamics of SiF C-2 Delta-B-2 Sigma(+) collision-induced transfer
Laser excitation on the C-2 Delta-(XII)-I-2 transition was used to prepare discrete rotational levels of the SiF C-2 Delta, v = 0 state, allowing their state-specific collisional behavior to be investigated. Time-and wavelength-resolved returning C-X fluorescence spectra established that the initial populations were only partially perturbed by rotationally 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 established, 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 substantial release of rotational energy during the transfer between electronic states. There is a positive correlation between the peak and average product j' and the initial rotational state j. The main features of the observed behavior are reproduced by a limiting impulsive model. We believe this to be a consequence of the respective valence and Rydberg characters of the C-2 Delta and B-2 Sigma(+) states.