LARGE ROTATIONAL ENERGY-RELEASE IN COLLISION-INDUCED SIF C-2-DELTA-B-2-SIGMA(+) VALENCE RYDBERG TRANSFER

Distinct rotational population distributions were prepared in SiF C-2 Delta, upsilon = 0 radicals by laser excitation. Collisions with H-2 o r N-2 transferred a fraction of the C-2 Delta molecules to the lower-l ying B-2 Sigma(+) state. B-X fluorescence spectra revealed the nascent rotational populations in the predominant B-2 Sigma(+), upsilon' = 0 level. An unusually large fraction of the available energy is released as SiF rotation, supplementing the initial SiF rotational angular mom entum. There is greater SiF B-2 Sigma(+) product rotation for N-2 than for H-2. A simple impulsive model is capable of rationalising these o bservations, consistent with previous vibrationally resolved measureme nts and the valence-Rydberg character of the transition.