Time Resolved Fluorescence from Parity Mixed Rotational Energy Levels: Collision vs Electric Field Effects

We describe time-resolved and spectrally-resolved laser-induced fluorescence measurements from the parity of A doublet levels of the A sup 1 II state of BCl radicals formed by CO sub 2 laser multiphoton dissociation of BCL sub 3 molecules. We show how the effects of collisional mixing can be discerned from the effects of electric field mixing. A set of rate equations for population transfer which include the effects of both field and collisional mixing are derived and compared to the more general theory of Alexander. Zero-field measurements of collisional mixing rates yield parity-changing rate constants whose J dependence is consistent with a dipole induced-dipole collision model: k sub ef=333,2.7,1.8, and 1.4x10 sup 6 sec sup -1 Torr sup -1 for Torr sup -1 for J'=3, 5, 11, and 18, respectively. These rate constants are then used in the rate equations to ascertain the extent of electric field mixing in high-field measurements.