Quantum beats due to coherently prepared acoustic vibrational modes ha
ve been observed for 14 to 17 nm diameter Au particles. The beat frequ
ency is inversely proportional to the particle size. The dephasing tim
e is ca. 15 ps, which is limited by the broad size distribution (+/-2
nm) of the samples. (C) 1998 American Institute of Physics. [S0021-960
6(98)70222-3].