Infrared Laser-induced Photodesorption and Ultraviolet Laser-induced Thermal Desorption of Methyl Fluoride from Polycrystalline Copper

Abstract

Laser-induced desorption of methyl fluoride from a polycrystalline copper surface has been achieved by either direct excitation of the γ3 vibrational mode of adsorbed methyl fluoride using a pulsed CO2 laser at 10μ or via heating of the copper substrate using a KrF excimer laser operating at 248 nm. We have previously demonstrated that at ultraviolet wavelengths, the reflectivity of copper is low enough that the KrF laser pulse of ~ 200 mJ deposits enough energy into the surface to desorb CO from either single crystal (100) or polycrystalline copper [1]. Time-of-flight (TOF) spectra have been characterized with respect to the CO translational velocity as a function of laser power density and CO coverage [2]. In the present work, preliminary results of such measurements are presented for the CH3F-Cu system.