title: Direct measurement of the angular dependence of the single-photon ionization of aligned N2 and CO2.
abstract: By combining a state-of-the-art high-harmonic ultrafast soft X-ray source with field-free dynamic alignment, we map the angular dependence of molecular photoionization yields for the first time for a nondissociative molecule. The observed modulation in ion yield as a function of molecular alignment is attributed to the molecular frame transition dipole moment of single-photon ionization to the X, A and B states of N2(+) and CO2(+). Our data show that the transition dipoles for single-photon ionization of N2 and CO2 at 43 eV have larger perpendicular components than parallel ones. A direct comparison with published theoretical partial wave ionization cross-sections confirms these experimental observations, which are the first results to allow such comparison with theory for bound cation states. The results provide the first step toward a novel method for measuring molecular frame transition dipole matrix elements.
authors.affiliation: JILA and Department of Physics, University of Colorado and NIST, Boulder, Colorado 80309, USA.
authors.forename: Isabell
authors.initials: I
authors.lastname: Thomann
authors.forename: Robynne
authors.initials: R
authors.lastname: Lock
authors.forename: Vandana
authors.initials: V
authors.lastname: Sharma
authors.forename: Etienne
authors.initials: E
authors.lastname: Gagnon
authors.forename: Stephen T
authors.initials: ST
authors.lastname: Pratt
authors.forename: Henry C
authors.initials: HC
authors.lastname: Kapteyn
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Murnane
authors.forename: Wen
authors.initials: W
authors.lastname: Li