The effect of point defects on the dynamics of a coherent acoustic phonon (E2g1 mode) in graphite was investigated by means of optical reflectivity measurements at fs time-resolution. The dephasing rate of the coherent E2g1 phonon increased linearly with increasing vacancy concentration. This was quantitatively explained by a scattering of the acoustic phonon by single vacancies. The vacancy-dependence of the dephasing-rate of the optical phonon was also considered.

Coherent Acoustic Phonon-Defect Scattering in Graphite. K.Ishioka, M.Hase, K.Ushida, M.Kitajima: Physica B, 2002, 316-317, 296-9