Yq. Liu et al., RADIOFREQUENCY SPECTROSCOPY OF ELECTRIC-FIELD SINGLET-TRIPLET ANTICROSSINGS OF HE-I, Journal of physics. B, Atomic molecular and optical physics, 27(11), 1994, pp. 120000239-120000243
Anticrossings of the 1s5d and 1s6d 1LAMBDA and 3LAMBDA Stark sublevels
of He I were investigated using radiofrequency spectroscopy. Single a
nd multiple photon transitions were induced and detected after excitat
ion of thermal He atoms by 10-20 keV ion impact. The energy separation
s of closest approach of four 1s5d and two 1s6d anticrossings were ded
uced from the resonance signals.