Magnesium atoms in an intense nonresonant laser field

A spectroscopic study on the nonresonant multiphoton ionization of magnesium atoms in a high-intensity laser field is reported. Both 0.532- and 1.06-μm radiation in the intensity regime of ${10}^{10}$–${10}^{13}$ W/${\mathrm{cm}}^2$ are used to produce both singly and doubly ionized magnesium ions. Mass and angularly resolved electron-energy analyses were used in an attempt to gain insight into the dominant mechanisms responsible for ionization. An analysis is presented for intensity- and frequency-dependent results, and electron angular distributions are reduced in terms of atomic parameters derivable from lowest-order perturbation theory. The results demonstrate the important influence that the details of the atomic structure have in describing the high-field nonresonant ionization of magnesium.