Abstract

X-ray absorption, in the form of chemical shifts and EXAFS measurements can interrogate selected elements to reveal their ionization states as well as the distances to nearby atoms, in principle on the ultrafast time scale. Shape resonances, which we have studied in the present experiment, are high amplitude absorption resonances in the near edge spectral region close to the absorption threshold for a particular shell, and occur in symmetrical molecules. The SF₆ molecule exhibits intense shape resonance lines at the sulfur K and L edges, due to multiple scattering and interference of the photoelectrons by the fluorine atoms symmetrically surrounding the central sulfur atom. As the molecule dissociates, losing F atoms and its high symmetry, the resonance should greatly diminish or disappear.

© 1996 Optical Society of America