Investigation of laser induced structures in multiphoton ionization of magnesium

We examine the effect of the excitation of an autoionizing state on electron spectra resulting from multiphoton-ionization. We study the case of above threshold three-photon ionization of magnesium in the region of the 3p3d ¹ P ⁰ resonance, with conditions similar to a two-colour experiment recently performed. The electron spectrum is compared to the partial spectrum corresponding to the region located just above the threshold (which is populated through two-photon absorption from a probing laser). The calculations confirm the experimental observations, a laser induced continuum structure (LICS) is observed in this partial spectrum. The interference process in examined in detail and a Fano-like parametrization of the two-photon ionization electron profile is proposed.