First experiments on field photodesorption IR spectroscopy

Abstract

The ion current of adsorbed water molecules is studied experimentally as a function of the frequency of near-IR radiation incident on a surface at frequencies in the intrinsic vibrational bands of the water molecule. The ions are produced by nonequilibrium field surface ionization. The observed band (near one of the combination frequencies) has a width of 100 cm−1 and is shifted relative to the free molecular band by 130 cm−1. Estimates show that the cross section for absorption of the radiation by the adsorbed molecules is 3–4 orders of magnitude larger than for free molecules, as is typical of surface processes.