Motional-Stark-effect-induced anticrossings

Atoms moving through a magnetic field suffer a Stark effect whose magnitude is dependent upon the atom's velocity. This velocity-dependent perturbation has recently been exploited as a Doppler narrowing technique, and in this paper we consider atomic anticrossings induced by it. Experimentally such anticrossings are observed between $n{}_{}{}^3{}_{}{}^{}D-n{}_{}{}^{1,3}{}_{}{}^{}F$ states of He for $n=4-9\mathrm{}$, with $n=8\mathrm{}$ being considered in detail. Theoretical expressions are derived for motional-Stark-effect-induced anticrossing line shapes. Good agreement with the observed line shapes is obtained and the theoretical analysis allows a value of the $n={}_{}{}^3{}_{}{}^{}D-{}_{}{}^{1,3}{}_{}{}^{}F$ interval to be obtained which is in good agreement with previous predictions.