The phonon spectrum of high energy heat pulses generated in thin metal films

The phonon spectrum of high energy heat pulses (10⁴W/cm²) generated by current pulses in thin evaporated metal films was studied in ruby by time resolved optical spectroscopy. The experiments show that the population temperature of the phonon states rises with rising phonon energies in accordance with theoretical predictions of Perrin and Budd [1, 2]. The thermalization of the phonon spectrum needs a time of approximately 900 µs in ruby flushed with cold helium gas.This work was supported by the Deutsche Forschungsgemeinschaft, SFB65