VIBRATIONAL DEPHASING DYNAMICS OF THE HYDROGENATED SI(100)-2X1 SURFACE REVISITED - MULTIMODE DEPHASING MODEL

Surface Raman scattering was performed on Si(100)-2 X 1:H. The analysi s of the temperature-dependent spectral profiles of the SiH stretch wi th the Persson-Rydberg dephasing model has led to an exchange mode (om ega(0)) at 647 +/- 79 cm(-1), a coupling parameter (delta omega) equal to - 30 +/- 8 cm(-1), and a friction parameter (eta(0)) equal to 59 /- 3 cm(-1). The extrapolated pure dephasing time at 100 K, however, w as found to be inconsistent with the direct time-resolved measurement [P. Guyot-Sionnest, P.H. Lin, E.M. Hiller, J. Chem. Phys. 102 (1995) 4 269], This controversy can be resolved by proposing another exchange m ode at similar to 200 cm(-1), coexisting with the one at similar to 65 0 cm(-1). This multi-mode dephasing model generalizes the existing sin gle-mode model. (C) 1998 Elsevier Science B.V. All rights reserved.