Isotope shift in the (2S01-2P11) line of atomic helium

A measurement of the isotope shift in the (2S01-2P11) line of atomic helium has been made and is in excellent agreement with theory. Both He4 and He3 2S01 metastable beams were irradiated in a magnetic field with 20 582 (2S01-2P11) radiation from He3 and He4 resonance lamps, respectively. In each case, a magnetic sublevel of the 2P11 state was Zeeman shifted so as to scan the resonance-lamp profile. The 584- (2P11-1S01)-decay photons served to monitor the excitation. A shift ν(He3)-ν(He4)=0.1408±0.0019 cm-1 was obtained. © 1971 The American Physical Society.