Abstract

Bound — free absorption of ultraviolet radiation by colliding pairs of rare gas-halogen atoms represents a potentially serious loss mechanism in the excimer lasers. This paper reports an investigation of the photoassociative production of KrF[Kr + F + ℏω)(248nm) → KrF(B)] in various Kr/F₂ mixtures in order to obtain an absolute cross section forthe process. The studies involved the use of two KrF lasers. The first laser (I₁ < 500 MW cm^-2) was used to dissociate F₂ and was fired ~1 μs prior to the firing of the second (l₂ < 100 MWcm^-2). The latter served to photoassociate the Kr-F collision pairs. Because of the efficient conversion of KrF(B) to Kr₂F(4²Γ), spontaneous emission from the Kr₂F(4²Γ) state was monitored to measure the photoassociation absorption strength. The intensity dependence of the photoassociation process was measured as a function of the intensity of each laser and the partial pressures of the reactants. The effective cross section obtained for the absorption is 3.2 × 10^-18 cm², a factor of 2 larger than the Kr₂F absorption cross section at 248 nm. Also investigated were the effect of the time delay between the two KrF lasers, rates for quenching of Kr₂F(4²Γ) by both Kr and F₂, and the wavelength dependence of the photodissociation effect. The impact of this process on KrF lasers is discussed.

© 1986 Optical Society of America