Transitions between Zeeman substates of excited He I levels induced by electric radiofrequency fields

Abstract

Making use of the large tensor polarizabilities of excited He I levels, transitions between Zeeman substates of 1 snd 1D 2 levels have been induced by electric radiofrequency fields after ion-impact excitation of He atoms. Resonance signals have been observed near the Larmor frequency co=coL as well as near co = 2co L. These signals are interpreted as 2-quantum electric-dipole (2El) transitions and 1El transitions, respectively, between the Zeeman sublevels with M=0 and M= _+2. The interaction of this 3-state system {IM); M=-2,0, +2} with the applied external fields (magnetic field H~ and static and alternating electric field gx=g0+gx coscot) is discussed. The shape of the resonance signals has been evaluated in the rotating field approximation. In contradiction to the theory, the observed signals show a peculiar narrow structure at the center of the signal which is not yet completely understood. The experimental techniques developed are expected to be useful for investigations of Zeeman-, Stark-, fine and hyperfine splittings of excited He I levels.

Analysis of impact-excited HeI states by applying magnetic and electric depolarization techniques

“…4b) from the level crossing signals (Fig. 3), the recording was fitted using a superposition of three Lorentz functions with a fixed FWHM AB¢=h/(z.gj.#B) where = 38.7 ns is the radiative lifetime of the 41D level [21]. Due to the deflection of the ion beam in the magnetic field B=, a slight linear slope of the background intensity had to be taken into account.…”

Precision measurement of the 1s 4f fine structure of HeI

“…For the measurements being considered in this paper, it is more favourable to apply this rf electric resonance technique than the rf magnetic resonance technique [6] usually used for high-resolution measurements of energy spacings between equal parity states. This can be seen by estimating the rf power [7] needed for each case.…”