PHOTOASSOCIATION OF KR-F COLLISION PAIRS IN THE ULTRAVIOLET

The bound<--free absorption (photoassociation) of thermalized (Kr(4p6 S-1(0))-F(2p5 2P))-S-1-P-2 collision pairs has been studied in the ult raviolet in Kr/F2 gas mixtures by laser pump-probe techniques. Experim ents carried out at 248 nm with two time-delayed excimer laser pulses demonstrate that KrF(B2 SIGMA1/2+) molecules are produced by the photo dissociation of F2, followed by the photoassociation of Kr-F collision pairs by a single approximately 5 eV photon. The saturation behavior of this photoassociation process indicates that the currently accepted value for the KrF(B --> X) stimulated emission cross section (2.6 X 1 0(-16) cm2) is too large by at least a factor of 2. A revised value fo r sigma(SE) of (1.2 +/- 0.6) X 10(-16) cm2 is suggested. By indirectly monitoring the temporal decay of the atomic fluorine number density o wing to reformation of F2, the rate constant for the recombination of F atoms in a Kr background by three-body (2F + Kr) collisions has been determined to be k(r) = 2 X 10(-32) cm6 s-1.