title: Coherent atomic motions in a nanostructure studied by femtosecond X-ray diffraction.
abstract: Reversible structural changes of a nanostructure were measured nondestructively with subpicometer spatial and subpicosecond temporal resolution via x-ray diffraction (XRD). The spatially periodic femtosecond excitation of a gallium arsenide/aluminum gallium arsenide superlattice results in coherent lattice motions with a 3.5-picosecond period, which was directly monitored by femtosecond x-ray pulses at a 1-kilohertz repetition rate. Small changes (DeltaR/R = 0.01) of weak Bragg reflexes (R = 0.005) were detected. The phase and amplitude of the oscillatory XRD signal around a new equilibrium demonstrate that displacive excitation of the zone-folded acoustic phonons is the dominant mechanism for strong excitation.
authors.affiliation: Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Bargheer
authors.forename: N
authors.initials: N
authors.lastname: Zhavoronkov
authors.forename: Y
authors.initials: Y
authors.lastname: Gritsai
authors.forename: J C
authors.initials: JC
authors.lastname: Woo
authors.forename: D S
authors.initials: DS
authors.lastname: Kim
authors.forename: M
authors.initials: M
authors.lastname: Woerner
authors.forename: T
authors.initials: T
authors.lastname: Elsaesser