Metastable Autoionizing Quartet- Quintet- and Sextet States in B

Abstract

In the past the observation of radiative transitions as well as autoionization of highly-excited states using beam-foil excitation (1) was preliminary confined to helium- and lithium- like ions (2,3). Due to specific selection rules some of these terms are metastable with respect to Coulomb autoionization. By detecting the secondary electron emission as a function of the distance from the foil to the spectrometer Sellin et al. (4) have shown that such levels have decay rates comparable to optical transitions. This method has led to the assignement of some spectral features arising from decays of Li-like quartet levels corresponding to oxygen, fluorine and chlorine beams (5). However two characteristic structures labeled originally A and B peak could not be identified as transitions of three-electron quartet states alone. Therefore Pegg et al. (6) and Junker and Bardsley (7) have suggested that these features might originate from Auger decays of Be-like quintet and B -like sextet levels.