Suppression of Multiphoton Ionization with Circularly Polarized Coherent Light

Multiphoton ionization in xenon has been studied with 1064-nm circularly polarized coherent light, producing electrons with energies up to 15 eV. A strong suppression of the cross section is observed for electrons below 4 eV, but not for linearly polarized light at the same intensity. We show that if the electrons are emitted in single-step, nonresonant coherent processes, rather than stepwise excitation, the centrifugal potential barrier in the atomic Hamiltonian produces this suppression.