A source of narrow bandwidth (<800 MHz) tunable laser radiation at 58.4 nm has been developed and is applied to record the 11S-21P transition in 3He and 4He. From the 4He transition frequency of 171 134.8936(58) cm-1 a fivefold improved ground state Lamb shift of 1.3763(58) cm-1 is deduced, in good agreement with the theoretical value of 1.3755(10) cm-1. The measured 11S-21P transition isotope shift of 263410(7) MHz presents a more than 2 order of magnitude improvement over a previous value and agrees with a theoretical value of 263411.26(11) MHz.
|Number of pages||4|
|Journal||Physical Review Letters|
|Publication status||Published - 19 Feb 1996|