Lyman- alpha(1) decay in hydrogenlike ions: interference between the E1 and M2 transition amplitudes

For the Lyman- alpha(1) transition (2p(3/2)-->1s(1/2)) in hydrogenlike ions an interference between the leading E1 decay channel and the much weaker M2 multipole transition gives rise to a remarkable modified angular distribution of the emitted photons from aligned ions. This effect is most pronounced for the heaviest elements but results in a still sizable correction for medium- Z ions. For the particular case of hydrogenlike uranium where the angular distribution of the Lyman- alpha(1) x rays following radiative electron capture has been measured, the former variance with theoretical findings is removed when this E1-M2 interference is taken into account.