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 glass and liquid. The pure dephasing temperature dependence is linear (T1) at very low temperature and an activated process (ΔE = 385 ± 50 cm−1) above 2≈ 20 K. Pure dephasing mechanisms are proposed. It is suggest that the T1 dependence arises from dynamics of the glassʹ two level systems, while the activated process involves coupling of the CO stretch to a low frequency intramolecular mode. The experimental results are contrasted with vibrational dephasing experiments on W(CO)6 also in dibutylphthalate.