Isotope shifts and pressure broadening have been measured in the two-photon transition at 249 nm from the 5p61S0 ground level of neutral xenon to a J=0 level of the 5p56p configuration (the 2p5 level in Paschen notation). A continuous-wave tunable dye laser operating at 498 nm with intracavity frequency doubling excited the transition. The work is the first application of Doppler-free laser spectroscopy to a transition involving the ground level of a rare gas. The results show that although no s electron is directly involved in the transition, the field isotope shifts are comparable with those observed in transitions of the type 6s-np. © 1989 IOP Publishing Ltd.
