Two-electron effects in the multiphoton ionization of magnesium with 400-nm 150-fs pulses

The multiphoton ionization and photoelectron spectra of magnesium were stud ied at laser intensities of up to 6 x 10(13) W cm(-2) using 150-fs laser pu lses of a wavelength of 400 nm. The results indicated that a variety of dif ferent ionization mechanisms played a role in both types of spectra. A theo retical model describing the processes is presented and the routes to ioniz ation are identified. The work demonstrates the significance of the two-ele ctron nature of the atom in interpreting the experimental results. [S1050-2 947(99)05711-X].