VIBRATIONAL ECHO STUDIES OF PURE DEPHASING - MECHANISMS IN LIQUIDS AND GLASSES

Temperature dependent vibrational dephasing experiments are presented on the asymmetric CO stretching mode (2010 cm(-1)) of (acetylacetonato )bicarbonylrhodium(I) in the solvent dibutylphthalate in both the glas s and liquid. The pure dephasing temperature dependence is linear (T-1 ) at very low temperature and an activated process (Delta E = 385 +/- 50 cm(-1)) above approximate to 20 K. Pure dephasing mechanisms are pr oposed. It is suggest that the T-1 dependence arises from dynamics of the glass' two level systems, while the activated process involves cou pling of the CO stretch to a low frequency intramolecular mode. The ex perimental results are contrasted with vibrational dephasing experimen ts on W(CO)(6) also in dibutylphthalate. (C) 1997 Elsevier Science B.V .