title: Dynamics of size-selected gold nanoparticles studied by ultrafast electron nanocrystallography.
abstract: We report the studies of ultrafast electron nanocrystallography on size-selected Au nanoparticles (2-20 nm) supported on a molecular interface. Reversible surface melting, melting, and recrystallization were investigated with dynamical full-profile radial distribution functions determined with subpicosecond and picometer accuracies. In an ultrafast photoinduced melting, the nanoparticles are driven to a nonequilibrium transformation, characterized by the initial lattice deformations, nonequilibrium electron-phonon coupling, and, upon melting, the collective bonding and debonding, transforming nanocrystals into shelled nanoliquids. The displasive structural excitation at premelting and the coherent transformation with crystal/liquid coexistence during photomelting differ from the reciprocal behavior of recrystallization, where a hot lattice forms from liquid and then thermally contracts. The degree of structural change and the thermodynamics of melting are found to depend on the size of nanoparticle.
authors.affiliation: Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA. ruan@pa.msu.edu
authors.forename: Chong-Yu
authors.initials: CY
authors.lastname: Ruan
authors.forename: Yoshie
authors.initials: Y
authors.lastname: Murooka
authors.forename: Ramani K
authors.initials: RK
authors.lastname: Raman
authors.forename: Ryan A
authors.initials: RA
authors.lastname: Murdick