It is shown that even for optical frequencies the dipole approximation is not always valid in multiphoton ionization. For certain photon frequencies, we find quadrupole-dipole contributions which are several orders of magnitude larger than the usual dipole-dipole contribution to two-photon ionization.

Physical Review LettersMar 17, 197548 citations

Physics Letters A

On the electric quadrupole interaction in multiphoton ionization of atoms

G. Laplanche, A. Durrieu, Y. Flank, A. Rachman

Published Nov 1, 1975• 6 citations

Publisher

DOI: 10.1016/0375-9601(75)90375-8

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5p

state is measured.

{\mathrm{}}^{2}

{D}_{3/2}

and 6d

{\mathrm{}}^{2}

{D}_{5/2}

electric quadrupole transitions and for one-photon resonant, three-photon ionization via the 5d

{\mathrm{}}^{2}

{\mathrm{D}}_{3/2}

and 5d

{\mathrm{}}^{2}

{D}_{5/2}

transitions. The ratios of the total ionization rates for linearly and circularly polarized light have also been measured for the 6d

{\mathrm{}}^{2}

{\mathrm{D}}_{3/2}

and 6d

{\mathrm{}}^{2}

{D}_{5/2}

states. A theoretical analysis and detailed comparison with the experimental results are given.