Multiphoton ionization of a three-electron atom: Studies with 25-keV Al beams

An alternative technique to obtain neutral-atom beams for multiphoton-ionization studies, via wavelength-selective photodetachment of negative ions, is described. This approach is illustrated by multiphoton ionization of Al(3s23p 2P) atoms with selected visible and uv laser pulses of ≤300 ps duration, and with intensities ∼109–6×1010 W/cm2. For visible wavelengths, single-electron ionization dominates, while excitation of doubly excited states …