First Experimental Evidence of Destructive Interference Effects in Two-Photon Ionization of Cs Atoms

Abstract

This Letter presents the first experimental evidence of destructive interference effects in multiphoton ionization. The experiment involves a Cs atomic beam crossed with a linearly polarized dye-laser beam whose intensity reaches 20 GW/${\mathrm{cm}}^{2}$ in the 460-540-nm wavelength range. As predicted by second-order perturbation theory, the generalized ionization cross section exhibits a deep minimum which is found to equal (9\ifmmode\pm\else\textpm\fi{}5)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}52}$ ${\mathrm{cm}}^{4}$ s at 480 nm. Discrepancies with previous experiments are tentatively explained.