Two-photon ionization cross sections from the rubidium ground state have been measured with both a cw 421-nm laser and a combination of cw 421- and 1002-nm lasers. The measurements were performed within a high-vacuum magneto-optical trap while the trapping lasers were switched off, exploiting the long trap lifetime and also the trap laser confinement. The two-photon cross sections were determined for the blue laser near resonance with the 6P<sub>1/2</sub> and 6P<sub>3/2</sub> states and compared with the estimates of a theoretical model. In near resonance with the 6P states, large two-photon photoionization cross sections were measured.
© 2004 Optical Society of America
Marco Anderlini, Emmanuel Courtade, Donatella Ciampini, Jörg H. Müller, Oliver Morsch, and Ennio Arimondo, "Two-photon ionization of cold rubidium atoms," J. Opt. Soc. Am. B 21, 480-485 (2004)