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

The multiphoton ionization and photoelectron spectra of magnesium were studied at laser intensities of up to 6×10¹³Wcm^-2 using 150-fs laser pulses of a wavelength of 400 nm. The results indicated that a variety of different ionization mechanisms played a role in both types of spectra. A theoretical model describing the processes is presented and the routes to ionization are identified. The work demonstrates the significance of the two-electron nature of the atom in interpreting the experimental results.