| Popis: |
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. |
