title: Role of Excited States In High-order Harmonic Generation.
abstract: We investigate the role of excited states in high-order harmonic generation by studying the spectral, spatial, and temporal characteristics of the radiation produced near the ionization threshold of argon by few-cycle laser pulses. We show that the population of excited states can lead either to direct extreme ultraviolet emission through free induction decay or to the generation of high-order harmonics through ionization from these states and recombination to the ground state. By using the attosecond lighthouse technique, we demonstrate that the high-harmonic emission from excited states is temporally delayed by a few femtoseconds compared to the usual harmonics, leading to a strong nonadiabatic spectral redshift.
authors.affiliation: Université de Bordeaux-CNRS-CEA, CELIA, UMR5107, F33405 Talence, France.|Institut National de la Recherche Scientifique, Centre EMT, J3X1S2 Varennes, Quebec, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Beaulieu
authors.affiliation: Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001, USA.
authors.forename: S
authors.initials: S
authors.lastname: Camp
authors.affiliation: Université de Bordeaux-CNRS-CEA, CELIA, UMR5107, F33405 Talence, France.
authors.forename: D
authors.initials: D
authors.lastname: Descamps
authors.affiliation: Université de Bordeaux-CNRS-CEA, CELIA, UMR5107, F33405 Talence, France.
authors.forename: A
authors.initials: A
authors.lastname: Comby
authors.affiliation: Université de Bordeaux-CNRS-CEA, CELIA, UMR5107, F33405 Talence, France.|Institut National de la Recherche Scientifique, Centre EMT, J3X1S2 Varennes, Quebec, Canada.
authors.forename: V
authors.initials: V
authors.lastname: Wanie
authors.affiliation: Université de Bordeaux-CNRS-CEA, CELIA, UMR5107, F33405 Talence, France.
authors.forename: S
authors.initials: S
authors.lastname: Petit
authors.affiliation: Institut National de la Recherche Scientifique, Centre EMT, J3X1S2 Varennes, Quebec, Canada.
authors.forename: F
authors.initials: F
authors.lastname: Légaré
authors.affiliation: Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001, USA.
authors.forename: K J
authors.initials: KJ
authors.lastname: Schafer
authors.affiliation: Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001, USA.
authors.forename: M B
authors.initials: MB
authors.lastname: Gaarde
authors.affiliation: Université de Bordeaux-CNRS-CEA, CELIA, UMR5107, F33405 Talence, France.
authors.forename: F
authors.initials: F
authors.lastname: Catoire
authors.affiliation: Université de Bordeaux-CNRS-CEA, CELIA, UMR5107, F33405 Talence, France.
authors.forename: Y
authors.initials: Y
authors.lastname: Mairesse