Dynamics of coherent phonons in bismuth generated by ultrashort laser pulses

Coherent phonon spectra of bismuth measured at temperatures from 10 to 295 K by a femtosecond pump-probe reflectivity technique were compared with the corresponding Raman-scattering spectra. The decay rate and frequency show almost the same behavior for the coherent and incoherent phonons. This result indicates that the decay process of the coherent optical phonons is dominated by the anharmonic decay (energy relaxation) and that the contribution of the pure dephasing is negligibly small.