reading the photoelectron β -parameter spectrum in a resonance region

The behavior of the dipole photoelectron angular distribution parameter βnl (ω) in the vicinity of autoionizing resonances is discussed. It is shown that from this behavior, surprisingly, many photoionization parameters that cannot be measured experimentally can be extracted. These are the energy positions and ordering of autoionizing resonance minima in the partial photoionization cross sections σl+1 and σl-1, the energies at which these two cross sections intersect, and signs and magnitudes of the cos (δl+1 - δl-1) (δl±1 being the phase shifts of the dipole photoionization amplitudes Dl±1, respectively) through the autoionizing resonance energy region. Based on this, a deeper interpretation of such effects as the width-narrowing, width-fluctuating, and q -reversal in the βnl parameter spectrum in the autoionizing resonance energy region is given. As an example, calculated data for partial photoionization cross sections σ3d→f and σ3d→p, and β3d parameters for 3d photoelectrons from Cr+ are presented. © 2007 The American Physical Society