Vibrational dephasing dynamics of the hydrogenated Si(100)-2×1 surface revisited: multi-mode dephasing model

Surface Raman scattering was performed on Si(100)-2×1:H. The analysis of the temperature-dependent spectral profiles of the SiH stretch with the Persson–Rydberg dephasing model has led to an exchange mode (ω0) at 647±79 cm−1, a coupling parameter (δω) equal to −30±8 cm−1, and a friction parameter (η0) equal to 59±3 cm−1. The extrapolated pure dephasing time at 100 K, however, was found to be inconsistent with the direct time-resolved measurement [P. Guyot-Sionnest, P.H. Lin, E.M. Hiller, J. Chem. Phys. 102 (1995) 4269]. This controversy can be resolved by proposing another exchange mode at ∼200 cm−1, coexisting with the one at ∼650 cm−1. This multi-mode dephasing model generalizes the existing single-mode model.