Amplified 150–300-fs laser pulses are applied to monitor the thermal modulation of the transmissivity of thin copper films. Non- equilibrium electron-lattice temperatures are observed. The process of electron-phonon energy transfer was time resolved and was observed to be 1–4 ps increasing with the laser fluence.

• Received 23 June 1986

DOI:https://doi.org/10.1103/PhysRevLett.58.1212