COHERENT PHONONS FROM THE CDW STATE IN ETA-MO4O11

The charge-density-wave (CDW) phase transition in eta-Mo4O11 is studie d by femtosecond time-resolved reflection. We observed coherent optica l phonons in the reflectivity signal in both the normal and the CDW st ates. Below the transition temperature T-c1, six vibrational modes wer e clearly detected. Fear of them, centered at 64, 78, 85, and 98 cm(-1 ), were enhanced below T-c1. We conclude that the generation of these coherent phonon modes are closely related to the CDW state. [S0163-182 9(98)50140-3].