Photoionization of Kr and Kr2 at 193 nm and 248 nm

A microwave absorption technique was used in conjunction with two excimer lasers to obtain photoionization cross sections of atomic and molecular krypton at several excimer laser wavelengths. The electron density arising from the resonantly-enhanced three-photon ionization of Kr (1S /sub o/ ) at 193 nm was observed to display a quadratic dependence on laser intensity which yielded an effective two-photon cross section of 1.4 . 10-32 cm4 - W-1. In a separate experiment, the single-photon photoionization cross sections of electronically excited atomic and molecular krypton were measured at 248 nm. Following the formation of the excited states produced by a 193 nm laser pulse, the increase of electron density due to the arrival of a 248 nm laser pulse was measured at two different time delays. The molecular and atomic cross sections were found to be 1.4 . 10-18 cm2 and 5.7 . 10-19 cm2, respectively