Observation of laser-induced collisional energy transfer in xenon-argon mixtures

By using a multiphoton ionization technique, we observed a laser-induced energy-transfer process of fifth order in Xe-Ar atoms. Through four-photon excitation of the 4f[5/2]J = 2 level of Xe in collision with a ground-state Ar atom and the absorption of one additional photon, the 5s[3/2]J = 1 level of Ar is excited and subsequently ionized. By coincidence the same photon energy required for four-photon excitation of the chosen state in Xe is also adequate for absorption by Ar during the Xe*-Ar collision, thus permitting observation of a fifth-order laserinduced energy transfer in a simple one-color experiment.