Determination of the 1s Lamb shift in one-electron argon recoil ions

Abstract

The authors report accurate measurements of 2p_3/2,1/2 to 1s (Lyman- alpha _1,2) transitions in Ar¹⁷⁺ produced by encounters with a U⁶⁶⁺ beam at 5.9 MeV/nucleon. The 'recoil' production mechanism eliminates the need for Doppler corrections while a wavelength accuracy of 5 p.p.m. relative to visible standards is attained through use of a transfer standard X-ray profile. This permits a 1.5% test of the 1s_1/2 Lamb shift as limited by model uncertainties arising from spectator electron satellites.