Vibrational energy transfer of chemisorbed ethyltrichlorosilane at the glass/air interface

Chemisorbed films of ethyltrichlorosilane (ETS) at the glass/air interface are studied by IR-excitation sum-frequency (SF) spectroscopy. Using two ind ependently tunable infrared pulses in combination with a visible upconversi on pulse for the SF-probing process, a time-resolved vibrational spectrosco py is accomplished for the molecular monolayer at the dielectric surface. R apid energy transfer in the CH-stretching region is observed with a time co nstant of 1.5 +/- 1 ps. The population relaxation of the CH3-stretching mod es is found to be bimodal with a decay time of T-1 = 4.5 +/- 1 ps, while th e ground state is re-populated rather slowly with 130 +/- 50 ps. (C) 1999 E lsevier Science B.V. All rights reserved.