C. Denise Caldwell

Aligment in low‐energy photionization

Ions or excited states generated by the absorption of a photon just above or below an inner shell threshold can be aligned if the angular momentum of the excited state is greater than 1/2. These states typically decay by electron emission, and the alignment, which can be a sensitive probe of the electron correlation in the system, is reflected in an anisotropy in the angular distribution of the Auger electrons. Examples of the consequences of this behavior will be given from high resolution measurements of the angular distribution for Auger electrons at selected phonon energies corresponding to excitations of the 3d electrons in Kr and 4d electrons in Xe. Special attention will be given to the off‐resonant absorption very close to the d5/2 threshold.

Details of electron correlation explored with VUV and soft X-radiation☆

Abstract One of the most successful applications of synchrotron radiation in the VUV and soft X-ray regions of the spectrum has been in the elucidation of details of electron correlations as they influence dynamics of photoionisation. With the improved resolution capabilities of new light sources, it becomes possible to examine these dynamics in even finer detail, exposing structure previously masked by experimental broadening. In addition, higher flux will make possible experiments on very dilute or transient species as well as types of experiments not feasible with older generation sources. Examples illustrating these possibilities will be drawn from recent results obtained using undulator radiation in the analysis of resonant Auger decay and double ionisation resulting from decay of excitations out of the 4d shell in xenon. In addition, prospects of future electron-electron coincidence experiments will be discussed.

Application of x‐ray lasers to current and future experiments in atomic and molecular physics

The use of intrinsically narrow‐banded, intense x‐ray lasers has the potential for a significant impact in atomic and molecular physics. As with any new technology, it is impossible to predict all the new information which may emerge as the technology develops. At least at the beginning it will be important for these lasers to have applicability to existing experimental methods, which can then exploit the new tool for experiments which are currently barely feasible with existing and planned sources of radiation in the high‐energy regime. Examples of these are: resonant Auger decay, particularly of dilute species, studied with electron spectrometry; multi‐photon processes involving the simultaneous utilization of two laser photons; and fragmentation experiments in which the high‐energy photon is one of a pump‐probe pair. Results from these experiments will go a long way to suggesting directions for future study.