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 sub-picosecond and picometer accuracies. In an ultrafast photoinduced melting, the nanoparticles are driven to a non-equilibrium 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.
@article{arxiv.0704.0990,
title = {Dynamics of Size-Selected Gold Nanoparticles Studied by Ultrafast Electron Nanocrystallography},
author = {Chong-Yu Ruan and Yoshie Murooka and Ramani K. Raman and Ryan A. Murdick},
journal= {arXiv preprint arXiv:0704.0990},
year = {2015}
}