The fine structure of helium levels , is determined by the microwave-optical method outlined in the preceding paper. Helium atoms are excited to by electron bombardment and the optical radiation is observed with a photomultiplier tube. The intensity of this radiation changes when radio waves induce transitions between the fine structure sublevels. The separation is found to be 658.0±1.0 Mc/sec, which is to be compared to the most recent optical estimates of 750±300 Mc/sec.
- Received 1 August 1956
- Published in the issue dated January 1957
© 1957 The American Physical Society