Ion–molecule reactions in mixtures of methane with carbon tetrafluoride

Abstract

Ion–molecule reactions have been measured for methane–carbon tetrafluoride mixtures of different composition using a quadrupole mass spectrometer with a high-pressure ion source. Concentration of methane in these mixtures ranged from 10% to 90% (at 10% increment). Primary ions CH 3 + , CH 4 + , F + , CF + and CF 3 + were produced by electrons with energy of 300 eV. Secondary ions CH 5 + , C 2 H 3 + , C 2 H 4 + , C 2 H 5 + , C 2 H 7 + and CF 3 + were observed as the result of ion–molecule reactions. Relative current intensities for primary and secondary ions are presented as a function of both total mixture pressure and concentration of methane in the mixture. Potential of repeller electrode inside the ion source collision chamber was fixed at 5 V for all measurements. Total mixture pressure was changed from 0.7 to 33.3 Pa. Schemes of ion–molecule reactions were proposed.