title: Polarization control in two-color above-threshold ionization of atomic helium.
abstract: Two-color multiphoton ionization of atomic helium was investigated by combining extreme ultraviolet (XUV) radiation from the Free Electron Laser in Hamburg with an intense synchronized optical laser. In the photoelectron spectrum, lines associated with direct ionization and above-threshold ionization show strong variations of their amplitudes as a function of both the intensity of the optical dressing field and the relative orientation of the linear polarization vectors of the two fields. The polarization dependence provides direct insight into the symmetry of the outgoing electrons in above-threshold ionization. In the high field regime, the monochromaticity of the XUV radiation enables the unperturbed observation of nonlinear processes in the optical field.
authors.affiliation: LIXAM, UMR 8624, CNRS-Université Paris Sud, Bâtiment 350, 91405 Orsay Cedex, France.
authors.forename: M
authors.initials: M
authors.lastname: Meyer
authors.forename: D
authors.initials: D
authors.lastname: Cubaynes
authors.forename: D
authors.initials: D
authors.lastname: Glijer
authors.forename: J
authors.initials: J
authors.lastname: Dardis
authors.forename: P
authors.initials: P
authors.lastname: Hayden
authors.forename: P
authors.initials: P
authors.lastname: Hough
authors.forename: V
authors.initials: V
authors.lastname: Richardson
authors.forename: E T
authors.initials: ET
authors.lastname: Kennedy
authors.forename: J T
authors.initials: JT
authors.lastname: Costello
authors.forename: P
authors.initials: P
authors.lastname: Radcliffe
authors.forename: S
authors.initials: S
authors.lastname: Düsterer
authors.forename: A
authors.initials: A
authors.lastname: Azima
authors.forename: W B
authors.initials: WB
authors.lastname: Li
authors.forename: H
authors.initials: H
authors.lastname: Redlin
authors.forename: J
authors.initials: J
authors.lastname: Feldhaus
authors.forename: R
authors.initials: R
authors.lastname: Taïeb
authors.forename: A
authors.initials: A
authors.lastname: Maquet
authors.forename: A N
authors.initials: AN
authors.lastname: Grum-Grzhimailo
authors.forename: E V
authors.initials: EV
authors.lastname: Gryzlova
authors.forename: S I
authors.initials: SI
authors.lastname: Strakhova