Direct observation of the Kr (3d(-1)4p(-1)) and Xe (4d(-1)5p(-1)) doubly charged ion states by threshold-photoelectron coincidence spectroscopy

Threshold-photoelectron coincidence spectra and threshold-photoelectron spectra are measured for Kr and Xe in the energy regions 105-127 and 75-100 eV, respectively. Kr2+3d-14p-1 and Xe2+4d-15p-1 doubly charged ion states are observed, and also Kr+3d-14p-1nl and Xe 4d-15p-1nl satellite states. To our knowledge, this is the first direct observation in electron spectroscopy of doubly charged ion states where one hole occurs in an inner shell and another in a valence shell. The results are compared with theoretical calculations performed with an algebraic Green's-function method, and also with previous experimental information from Auger electron spectroscopy.