Vibrational relaxation of adsorbate and adsorbent in the CO-adsorbed DM-20 zeolite system

We made the first observation of transient vibrational spectra of both adsorbate and adsorbent at molecule-adsorbed surface using a two-color infrared picosecond laser system. The transient measurements were carried out on the CO-adsorbed surface hydroxyl group (OD) of DM-20 zeolite by pumping the CO stretching mode (2175 cm(-1)) or OD stretching mode (2470 cm(-1)) and probing over the CO and OD stretching region (2000-2700 cm(-1)). The T(1) lifetime for OD was 5.8 ps and that for CO was 540 ps. By comparison with other CO-adsorbed systems, vibrational relaxation mechanisms of CO on various surfaces are discussed. We also found evidence of energy flows from the vibrational mode of the adsorbent (OD stretching) to that of the adsorbate (CO stretching) via van der Waals interaction. (C) 2003 Elsevier Science B.V. All rights reserved.