Search for the spectrally narrow radiative decay of 2p³⁴S^o_3/2in He^-

Abstract

Radiative autoionization (RA) of the 2p3 4So state in the He- ion has been predicted to result in a narrow spectral feature near lambda =32.315 nm. The authors have observed a weak, line-like structure at lambda =(32.32+or-0.02) nm, in spectra of foil-excited He ions at incident energies in the range 140-200 keV. This would be the first observation of this elusive RA process. The measurements and supportive evidence are presented as well as preliminary results for electronically similar ions of B and C, in which the decay is taking place connecting bound states, as in the well studied cases of Li and Be.