Interference peaks in collisional activation mass spectra: The loss of CH3˙ from [C13H9] ions

Abstract It was concluded from earlier metastable ion and collisional activation experiments that [C 13 H 9 ] + ions generated by dissociative ionization of stilbenes and diphenylmethane consist of a mixture of isomeric structures. It is shown in this paper that the methyl loss upon which this conclusion rests originates to a large extent from metastable molecular ions decomposing in the magnetic sector field (interference signal). Our results do not show, nor do they require, that more than one isomeric [C 13 H 9 ] + species is present. The importance of recognizing such interference signals is stressed.