MASS-SPECTROMETRIC DETECTION OF NEUTRAL RADICALS IN A CH4 MICROWAVE-DISCHARGE BY USE OF LI+ ION ATTACHMENT TECHNIQUES

The chemical species of the neutral radicals in the methane microwave (MW) discharge plasma were studied by quadrupole mass spectrometry in combination with a Li+ ion attachment technique. The approach is to have a MW discharge flow pass a lithium ion emitter and then to analyze, by quadrupole mass spectrometry, all ions formed by lithium ion attachment. Mainly, radicals such as CnH2n+1 (n=2-11) and CnH2n-1 (n=2-11) were detected. Species such as C4H3, C5H5, and C6H5 may also be produced in the process. Many such species have been identified for the first time. The presence of these species is evaluated by comparison with results from optical spectroscopy and threshold ionization mass spectrometry.