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Atomic and molecular materials exhibit complex behavior when exposed to strong externally applied fields. This research goal is to understand the nonlinear processes governing the coupling of intense radiation to atomic and molecular matter. The general amplitude under study is N gamma + X yields X superscript q+ + qe(-) + gamma', a class of processes which involves ionization with the collateral production of energetic electrons and radiation. Recently developed ultraviolet light sources are enabling the attainment of focal intensities such that the strong field regime can now be systematically studied. It was anticipated that such conditions would produce unusual excited states of matter and that expectation has been confirmed by recent experimental findings revealing the direct multiphoton production of inner-orbital (2 sigma/g) excited states of N2+ and N2(2+). Indeed, it can be shown that the strong-field coupling represents a unique mode of interaction which combines (1) the application of strong electromagnetic forces with (2) a very small collateral transfer of energy. This regime is impossible to achieve with charged particle collisions or with low intensity radiation of any frequency. Interactions of this type are particularly effective in exciting electronic motions along specific molecular axes enabling the generation of new forms of highly excited matter regardless of molecular structure or composition.

Multiquantum ultraviolet processes utilizing the available ultrahigh spectral brightness rare gas halogen technology can be used to generate inversion densities 10 to the 15th power/cu cm in the 10-20 eV range. On the basis of current experimental findings we conclude that these nonlinear methods of excitation can be successfully extrapolated to excitations in the 20-50 eV range, the region of excited atomic inner-shell configurations. (Author)

X-Ray and Auger transition probabilities were calculated for atoms that have been singly and multiply ionized in inner shells. The effects of relativity and configuration interaction on these rates were studied, and lifetimes of atomic inner-shell holes were computed. Synchrotron radiation was employed for precision measurements of atomic level energies, for the study of inelastic scattering, and for the investigation of sub-threshold excitation of atomic hole states. (Author)