The structure of triply excited, negative-ion resonances in the autoionizing region of helium

The formation and decay of the two lowest-lying, triply excited resonances in the autoionizing region of the helium spectrum (57-60 eV) have been studied by measuring electron-impact excitation functions for the n = 2 singly excited states of helium as a function of electron scattering angle. These results offer unambiguous confirmation of the classification of these states as and , respectively. Furthermore, the observation of the relative strengths of the decay of these features into the various final states enables some speculation as to the structure of the three excited electrons.