INELASTIC-COLLISION DYNAMICS OF VIBRATIONALLY EXCITED I-2(X)

Rotational and vibrational energy transfer rate constants have been me asured for excited rovibrational levels of I-2(X). Stimulated emission pumping was used to excite the levels upsilon = 23, J = 57, and upsil on = 38, J = 49 via the B-X transition. Laser induced fluorescence fro m the D-X system was used to follow the collision dynamics. Energy tra nsfer processes induced by collisions with He,Ar,N-2,O-2,Cl-2,I-2, and H2O were investigated. Rotational energy transfer was found to be eff icient for all collision partners. In accordance with classical models , the total rotational transfer rate constants were proportional to th e collision momentum (except for H2O). The total transfer rate constan ts and the distributions of rotational levels populated by collisions were not dependent on the initial vibrational state. For colliders tha t are not good quenchers of I-2(B), the rotational energy transfer dyn amics of the X and B states were found to be very similar. For collide rs that are good quenchers, comparisons of the X and B state dynamics show that quenching competes with rotational energy transfer in the B state. Vibrational energy transfer was characterized for all collision partners with the exception of I-2, which appears to have a low vibra tional transfer efficiency. Vibrational transfer was dominated by Delt a upsilon = - 1 steps. Multiquantum vibrational transfer was not obser ved. The dependence of the vibrational transfer rate constants on the initial vibrational state appeared to be weaker than the linear scalin g predicted by the Landau-Teller model. Vibrational deactivation of I- 2(X) plays an important role in chemically driven oxygen-iodine lasers . Effective deactivation late constants have been derived from the vib rational transfer rate constants. Estimates for the deactivation rate constants for O-2 and H2O differ from those currently in use by almost an order of magnitude. (C) 1997 American Institute of Physics.