Teijo Åberg

Quantum theory of post-collision interaction in inner-shell photoionization

We have performed fully quantum-mechanical and relativistic calculations of the post-collision-interaction effect in x-ray-induced argonK−L2L3(1D) Auger and xenonL2−L3N4(J=3) Coster-Kronig-electron emission. The Dirac-Fock computations include a complete integration over intermediate one-hole continuum states in the lowest-order expression of the resonant double-photoionization cross section. The results are in excellent agreement with synchrotron-radiation measurements of the post-collision-interaction shifts. We have also made nonrelativistic Hartree-Fock test calculations of the argonK−L2L3(1D) and xenonL3−M4M5(1G4) Auger-electron line shapes. The quantum-mechanical results are compared with rigorous semiclassical calculations which have been made without using the stationary-phase approximation. The results of this computational analysis are interpreted in terms of an analytical line-shape formula based on asymptotic Coulomb wave functions. As a consequence the most salient features of the post-collision interaction in inner-shell photoionization are explained.

Atomic-structure effects in strong-field multiphoton detachment and ionization

Above-threshold photoelectron detachment and ionization spectra are investigated theoretically in the tunneling and over-barrier regime as a function of wavelength (≥1.064 μm) and polarization of the electromagnetic field. It is found that the zeros in the initial-state wave function can drastically affect the shape of the high-energy photoelectron distribution. The phenomenon is not predicted by tunneling and related models and hence can test their validity and reveal whether Keldysh-type theories are in general applicable to strong-field multiphoton dynamics.