The technique of picosecond electron diffraction is used to resolve in time the laser-induced melting of thin aluminum films. It is observed that under rapid heating conditions, the long-range order of the lattice subsists for lattice temperatures well above the equilibrium point, indicative of superheating. The melting time is found to vary according to the degree of superheating. The initial density of nuclei is determined under the assumption of a two-dimensional expansion model. These results show for the first time the relationship between superheating and the rate of transformation.

• Received 19 March 1984

DOI:https://doi.org/10.1103/PhysRevLett.52.2364