Surface heterogeneity and inhomogeneous broadening of vibrational line profiles.

The surface heterogeneity of amorphous silica (aSiO2) has been probed using coverage dependent temperature programmed desorption (TPD) of a simple probe molecule, carbon monoxide (CO). The resulting distribution of interaction energies is the foundation from which an environmentally broadened vibrational line profile synthesis has been undertaken. These simulations are compared with measured line profiles recorded at 0.1 cm-1 resolution using reflection-absorption infrared spectroscopy (RAIRS). A comparison of such line profile synthesis for CO on amorphous silica and on porous amorphous solid water (p-ASW) is also reported and conclusions are drawn as to the vibrational relaxation and surface dynamics of the CO molecule on the two surfaces.