title: High harmonic generation from multiple orbitals in N2.
abstract: Molecular electronic states energetically below the highest occupied molecular orbital (HOMO) should contribute to laser-driven high harmonic generation (HHG), but this behavior has not been observed previously. Our measurements of the HHG spectrum of N2 molecules aligned perpendicular to the laser polarization showed a maximum at the rotational half-revival. This feature indicates the influence of electrons occupying the orbital just below the N2 HOMO, referred to as the HOMO-1. Such observations of lower-lying orbitals are essential to understanding subfemtosecond/subangstrom electronic motion in laser-excited molecules.
authors.affiliation: PULSE Institute, SLAC, Menlo Park, CA 94025, USA, and Departments of Physics and Applied Physics, Stanford University, Stanford, CA 94305, USA.
authors.forename: Brian K
authors.initials: BK
authors.lastname: McFarland
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Farrell
authors.forename: Philip H
authors.initials: PH
authors.lastname: Bucksbaum
authors.forename: Markus
authors.initials: M
authors.lastname: Gühr