Recent advances in X-ray instrumentation have made it possible to measure the
spectra of an essentially unexplored class of electronic states associated
with double inner-shell vacancies. Using the technique of single electron
spectroscopy, spectra of states in CS2 and SF6 with a double hole in the
K-shell and one electron exited to a normally unoccupied orbital have been
obtained. The spectra are interpreted with the aid of a high-level theoretical
model giving excellent agreement with the experiment. The results shed new
light on the important distinction between direct and conjugate shake-up in a
molecular context. In particular, systematic similarities and differences
between pre-edge states near single core holes investigated in X-ray
absorption spectra and the corresponding states near double core holes studied
here are brought out
