LASER-ABLATION OF GRAPHITE IN AN OXYGEN JET

Mass spectroscopic studies on a reactive laser ablation of graphite at 1064 nm in a pulsed oxygen jet have been performed. Significant chang es in the relative enrichment of carbon ions including anomalous enric hment of C-2(+) ions as well as formation of CO+, C2O+, and C3O+ ions are observed. Collision-induced dissociation and reactive scattering o f carbon ions prevail by injection of the oxygen jet to the carbon plu me. Energetics of the ions is studied by using a time-of-flight quadru pole mass spectroscopy. Time-of-flight (TOF) spectra of each carbon io n consist of a fast and a slow component, which are considered to repr esent different formation mechanisms. By analyzing the changes of TOF spectra as a function of the delay time between the laser pulse and ox ygen jet, we examine the effects of collisions on the formation of car bon ions. (C) 1998 American Institute of Physics. [S0021-9606(98)00142 -1]