Physical Review A
The Lamb shift of He+ is derived from the measured anisotropy in the electric-field-induced quenching radiation of the metastable 2s12 state. The results demonstrate that the anisotropy method can be applied with high precision to one-electron ion beams, as well as neutral beams. We find a Lamb shift of 14040.22.9 MHz (1 standard deviation). The sources of error and difficulties encountered in working with ion beams are discussed in detail. © 1979 The American Physical Society.
Drake, Gordon W. F.; Goldman, S. P.; and Van Wijngaarden, A.. (1979). He+ lamb-shift measurement by the quenching-radiation anisotropy method. Physical Review A, 20 (4), 1299-1306.