Two flashlamp-pumped, tunable, dye lasers have been utilized to study three-photon ionization in atomic sodium. The resulting ion yield shows large peaks at laser frequencies which correspond to electric quadrupole transitions. This is the first direct observation of electric quadrupole effects in multiphoton ionization. The 3p 2 Pz/2~^^f niatrix element is determined, and the fine-structure splitting of the 5p state is measured.
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