MOLECULAR-BEAM STUDIES ON THE LASER-ENHANCED REACTION OF CHLORINE WITH A COPPER SURFACE AT 1064 NM

The laser-enhanced chemical reaction of Cl2 with a Cu surface has been investigated using time-resolved mass spectrometry. Mass and time-of-flight (TOF) distributions of the reaction products are measured while a polycrystalline Cu surface is exposed concurrently to a CW supersonic molecular beam of Cl2 at different translational energies and pulsed laser radiation at 1064 nm. The major neutral desorption products observed in the TOF spectra are Cu3Cl3 and CuCl. These TOF spectra can be simulated by Maxwell-Boltzmann distributions. The desorption yields of Cu3Cl3 and CuCl have been determined as a function of laser fluence and the translational energy of the incident Cl2. Both laser fluence and translational energy of the Cl2 markedly enhance the reaction of Cl2 with the Cu surface. The mass distribution of the products of the "dark" thermal reaction of Cu-Cl2 has also been measured by modulated molecular beam mass spectrometry. Cu3Cl is the dominant product in the thermal reaction with Cu3Cl3 and CuCl present in lesser amounts. A possible mechanism for the laser-enhanced reaction of Cu-Cl2 mainly consists of the dissociative chemisorption of Cl2 on the Cu surface, diffusion of chlorine into the Cu bulk, and laser stimulated thermal desorption. © 1990.