Multivacancy Effects in Atomic and Molecular Spectra

Chemical applications of X-ray spectra are inhibited by the general occurrence of multivacancy processes. These manifest themselves in emission ·spectra as extra lines (or satellites) while opening of channels to these initial configurations leads to extra detail in absorption spectra. While there are a few simple cases where this situation has been more or less fully discussed, the more interesting areas are those which are both not simple and not understood. There is, however, a fairly general experimental procedure by which this .complex situation could, in principle, be clarified. This involves carrying out high resolution emission spectroscopy as a function of exciting photon energy in regions containing both single and multiple vacancy thresholds. In earlier work summarised here, it was possible to demonstrate the procedure for a monatomic gas, argon. Subsequently, we have built and now operate a beamline designed specifically for such studies at the National Synchrotron Light Source (NSLS) in Brookhaven. Very recent results from this line and from a few experiments using conventional sources are summarised.