Infrared laser stimulated desorption of pyridine from silver surfaces

Abstract

In this report, we present the first study of resonantly stimulated desorption of pyridine from silver surfaces excited by polarized CO2 laser radiation. The desorption behavior has been investigated with surface enhanced Raman scattering (SERS), mass spectrometry, conventional thermal desorption and X-ray photoemission spectroscopy. It is observed that when the ring mode vibration of pyridine molecules adsorbed on silver island films at either 15K or 95K is excited by CO2 laser pulses in 1025 ∼ 1042 cm-1 frequency region, pyridine desorption from the metal surfaces is readily detected by these surface techniques. The desorption yield per laser pulse increases nonlinearly with the laser intensity and is strongly dependent on the polarization of the incident radiation. Namely, the p-polarized light is much more effective than the s-polarized light in inducing the desorption. The results clearly show the important role played by the vibrational excitation of adsorbed species in the observed desorption phenomenon.