title: Ultrafast soft-mode driven charge relocation in an ionic crystal.
abstract: Transient electron density maps of potassium dihydrogen phosphate (KH(2)PO(4), KDP) are derived from femtosecond X-ray powder diffraction patterns. Upon photoexcitation, the low-frequency TO soft mode is elongated impulsively and modulates the electronic charge distribution on the length scale of interatomic distances, much larger than the vibrational amplitude. The results demonstrate a charge transfer from the volumes around the P-atoms and K(+)-ions to those containing the O-HO units and a quadrupolar distortion of the K(+) charge distribution. This behavior reflects the interplay of nuclear motions and electric polarizations in the ionic crystal lattice.
authors.affiliation: Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-St. 2 a, Berlin, 12489, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Zamponi
authors.forename: J
authors.initials: J
authors.lastname: Stingl
authors.forename: M
authors.initials: M
authors.lastname: Woerner
authors.forename: T
authors.initials: T
authors.lastname: Elsaesser