Mass spectrometric analysis of the neutral products in a C2H4 microwave plasma: carbon carbenes and aromatic compounds

Product analysis in a microwave C2H4 discharge by Li+ ion attachment mass spectrometry, has made possible the detection of many unfamiliar hydrocarbon neutral products. Among them, many carbon carbenes up to C9H2, which may be formed by the addition of successive C2H4 molecules, have been identified mass spectrometrically. Species having an aromatic ring such as C6H5, C6H6 and C7H8, may also be produced, while various polymer free radicals such as CnH3 (n = 2, 4, 6), CnH5 (n = 2−5), CnH7 (n = 3, 4, 5, 7) and CnH9 (n = 4, 5) have been detected, where n is the carbon number. On the basis of these results we discuss the chemical reaction pathways in a C2H4 microwave plasma.