Photoassociation of Kr-F collision pairs in the ultraviolet

The bound←free absorption (photoassociation) of thermalized Kr(4p6 1S0)–F(2p5 2P) collision pairs has been studied in the ultraviolet in Kr/F2 gas mixtures by laser pump–probe techniques. Experiments carried out at 248 nm with two time‐delayed excimer laser pulses demonstrate that KrF(B2 Σ1/2+) molecules are produced by the photodissociation of F2, followed by the photoassociation of Kr–F collision pairs by a single ∼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 (2.6×10−16 cm2) is too large by at least a factor of 2. A revised value for σSE of (1.2±0.6)×10−16 cm2 is suggested. By indirectly monitoring the temporal decay of the atomic fluorine number density owing 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 kr=2×10−32 cm6 s−1.

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