Multiphoton ultraviolet spectroscopy of some6plevels in krypton

The observation of two-photon excitation of selected $6p$ levels in krypton atoms using tunable ArF* laser radiation at 193 nm is reported. Using time-resolved detection of visible fluorescence lines in the vicinity of 430 nm arising from $6p-5s$ transitions, radiative lifetimes for the $6p{\left[\frac{1}{2}\right]}_0$ and $6p{\left[\frac{3}{2}\right]}_2$ states of 123 ± 5 and 115 ± 5 nsec, and collisional self-quenching rates of (4.1 ± 0.4) × ${10}^{-10\mathrm{}}$ ${\mathrm{cm}}^3$/sec and (6.7 ± 0.7) × ${10}^{-10\mathrm{}}$ ${\mathrm{cm}}^3$/sec, respectively, have been determined. By carefully measuring the visible fluorescence intensity as a function of incident laser intensity, the photoionization cross section of the $6p{\left[\frac{3}{2}\right]}_2$ state has been established as (3.2 ± 2.0) × ${10}^{-19\mathrm{}}$ ${\mathrm{cm}}^2$.. The two-photon transition rates for both states have been theoretically calculated, and good agreement is found with measurements of the relative excitation rates for the two transitions.