Hyperfine structure in helium-3

Abstract

The authors have measured the hyperfine structures of the n3S (n=4-6) and n3D (n=3-6) levels of 3He. The accuracy of their data, obtained using Doppler-free two-photon spectroscopy, is more than one order of magnitude better than the previous one. They have also observed the intercombination line 23S-31D which has allowed them to measure the 31D-33D singlet-triplet distance.