Odd-Coherence in Beam-Foil Excitation of He⁺ Ion

Abstract

This paper presents measurement of polarized photon emission from the foil-excited ⁴He⁺ ion in an external static electric field parallel to the ion beam. Strong asymmetry was observed when the direction of the external field is reversed. The result is interpreted in terms of coherent superposition of excited states of opposite parity.