Professor Christopher Foot

Abstract:

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.

Abstract:

CW Doppler-free two-photon spectroscopy was used to measure the 1S-2S transition frequency in atomic hydrogen gas with a precision of six parts in 10**1**0. The result for the energy level separation is f(1S-2S) equals 2 466 061 413. 8 (1. 5) MHz and can be used to extract a value of the 1S Lamb shift. Choosing a value of the Rydberg constant measured independently by high-resolution spectroscopy of the hydrogen Balmer- beta transition, a value of DELTA f//L//a//m//b(1S) equals 8 173. 3 (1. 7) MHz was obtained, in good agreement with the theoretical prediction of 8 173. 06 (20) MHz. The experimental result can be interpreted as a measurement of the Rydberg constant. A value of R// infinity equals 109 737. 315 (7) cm** minus **1 was obtained, in agreement with recent precise measurements.