New observables for parity violation in atoms: Energy shifts in external electric fields

Abstract We consider hydrogen-like atoms in unstable levels of principal quantum number n = 2, confined to a finite size region in a non-homogeneous electric field carrying handedness. The interplay between the internal degrees of freedom of the atoms and the external ones of their c.m. motion can produce P-odd contributions to the eigenenergies. The nominal order of such shifts is 10−8 Hz. Typically such energy shifts depend linearly on the small P-violation parameters δ i ⋍ 10 −12 (i = 1, 2), essentially the ratios of the P-violating mixing matrix elements of the 2S and 2P states over the Lamb shift, with i = 1 (i = 2) corresponding to the nuclear spin independent (dependent) term. We show how such energy shifts can be enhanced by a large factor in a resonance-like way for special field configurations where a crossing of unstable levels occurs, leading to P-violating effects proportional to δ i . This is illustrated by explicit results for 11H, where we calculate a shift of 10−5 Hz. Measurements of such effects can give information concerning the “spin crisis” of the nucleons.