title: Soft X-ray-driven femtosecond molecular dynamics.
abstract: The direct observation of molecular dynamics initiated by x-rays has been hindered to date by the lack of bright femtosecond sources of short-wavelength light. We used soft x-ray beams generated by high-harmonic upconversion of a femtosecond laser to photoionize a nitrogen molecule, creating highly excited molecular cations. A strong infrared pulse was then used to probe the ultrafast electronic and nuclear dynamics as the molecule exploded. We found that substantial fragmentation occurs through an electron-shakeup process, in which a second electron is simultaneously excited during the soft x-ray photoionization process. During fragmentation, the molecular potential seen by the electron changes rapidly from nearly spherically symmetric to a two-center molecular potential. Our approach can capture in real time and with angstrom resolution the influence of ionizing radiation on a range of molecular systems, probing dynamics that are inaccessible with the use of other techniques.
authors.affiliation: JILA, University of Colorado, Boulder, CO 80309-0441, USA.
authors.forename: Etienne
authors.initials: E
authors.lastname: Gagnon
authors.forename: Predrag
authors.initials: P
authors.lastname: Ranitovic
authors.forename: Xiao-Min
authors.initials: XM
authors.lastname: Tong
authors.forename: C L
authors.initials: CL
authors.lastname: Cocke
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Murnane
authors.forename: Henry C
authors.initials: HC
authors.lastname: Kapteyn
authors.forename: Arvinder S
authors.initials: AS
authors.lastname: Sandhu