Above-threshold ionization near the3p4dFo1autoionizing state in magnesium

Abstract

Two-photon above-threshold ionization (ATI) relative cross sections from the $3\phantom{\rule{0.2em}{0ex}}^{1}P$ state of Mg have been measured using two-color ionization in the focus of a magnetic bottle spectrometer and have been calculated using the Green's-function method in the Feshbach formalism and an ${L}^{2}$-integrable close-coupling approach, with a basis of ${L}^{2}$-integrable $B$-spline functions. We report these cross sections in the region of $3d4p$ $^{1}F^{o}$ autoionizing state, with photon energies of $3.3--3.6\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. This is one of the few direct comparisons between ab initio theory and experiments in ATI in the vicinity of a Feshbach resonance. A good agreement between theory and experiment is found in the relative total cross sections.