Multiphoton Ionization of Magnesium in a Ti-Sapphire laser field

In this paper we report the theoretical results obtained for partial ionization yields and the above-threshold ionization (ATI) spectra of Magnesium in a Ti:sapphire laser field (804 nm) in the range of short pulse duration (20-120 fs). Ionization yield, with linearly polarized light for a 120 fs laser pulse, is obtained as a function of the peak intensity motivated by recent experimental data \cite{gillen:2001}. For this, we have solved the time-dependent Schr\"{o}dinger equation nonperturbatively on a basis of discretized states obtained with two different methods; one with the two-electron wavefunction relaxed at the boundaries, giving a quadratic discretized basis and the other with the two-electron wavefunction expanded in terms of Mg$^+$-orbitals plus one free electron allowing the handling of multiple continua (open channels). Results, obtained with the two methods, are compared and advantages and disadvantages of the open-channel method are discussed.