Coherent excitation of cadmiumJ=0,1,2 autoionizing levels by electron impact

We have measured (e,2e) energy spectra in cadmium for the 4${\mathit{d}}^9$5${\mathit{s}}^2$5p J=1 autoionizing region. The ejected-electron energy range investigated was from 2.6 to 4.8 eV with an incident electron energy of 150 eV and a scattering angle of 3°. Small differences were found in spectra taken at ejected-electron directions 180° apart. We ascribe these differences to interference terms arising from coherent excitation of the J=1 and overlapping 5pnp J=0,2 autoionizing levels. A calculation of these effects is presented that agrees quite well with the experimental data. We obtain experimental excitation amplitude ratios and assign a previously undetected autoionizing level to 5p6p ${}_{}{}^3{}_{}{}^{}$ ${\mathit{D}}_2$.