Abstract
We measure the frequency of the transitions of helium in a metastable beam using an optical frequency comb synthesizer. The relative uncertainty of these measurements ranging from to is, to our knowledge, the most precise result for any optical helium transition. Considering existing accurate values of the fine structure, we measure a centroid value of the frequency of 276 736 495 624.6(2.4) kHz, improving the previous interferometric measurement by 30 times. New accurate values of the and Lamb-shift energies are obtained.
- Received 28 April 2003
DOI:https://doi.org/10.1103/PhysRevLett.92.023001
©2004 American Physical Society