THEORY AND COMPUTATION OF THE PROFILE OF THE FREE-FREE TRANSITION-PROBABILITY BETWEEN AUTOIONIZING (RESONANT) STATES

We have derived the general expression for the energy-dependent cross section of the transition between two resonant states in the continuou s spectrum of atoms and molecules, under the physically meaningful con ditions of broadband excitation. The profile is expressed in terms of a symmetric, an asymmetric and a background component, and is cast in a form containing as limiting cases the discrete-discrete Lorentzian p rofile and the discrete-resonance Beutler-Fano profile. The theory has been implemented numerically by ab initio, methods on the transition He* '2s2p' P-1(0) --> '2p3p' D-1, for tunable radiation hv around 3.4 eV.