‘Doubly charged ion’ mass spectra of some simple aromatic compounds

Abstract

Benzene, toluene, phenol, diphenyl ether and the three isomeric dihydroxy-benzenes have been examined using an MS-9 mass spectrometer under conditions that allowed only ions having twice the normal amount of kinetic energy to be detected. These ions are, in fact, singly charged ions arising from charge exchange reactions of doubly charged ions of the same mass, occurring in the first field free region of the spectrometer. It is argued that the spectra obtained yield essentially the distribution of doubly charged ions in the source region. These 'doubly charged ion' mass spectra are compared with the normal singly charged ion spectra of the compounds and the implications of the significant differences that are found, are discussed.

Some aspect of the doubly‐charged ion chemistry of armoatic amines and diamines

“…While the variation of the nature of the collision gas causes changes in the overall efficiency of the charge-exchange process, all of the above-mentioned substances were effective as collision gases, except helium and neon. This can be rationalized on the basis of the energy balance of reaction (1). Since no kinetic energy loss of the m++ ions is observed, when they are converted to m+ ions, the energy necessary to ionize the collision gas molecule must come from the energy gain of the process m* -+ m+, which is the difference between the single and the double ionization potentials of m. These values are seldom known for organic compounds and their fragments, but it is reasonable to assume that the majority will fall into the range around 16 to 18 eV.…”

“…The details of the mechanism of the charge-exchange process are not known and various ions, especially evenus. oddelectron ions, may exhibit different cross sections for reaction (1). Therefore, while we believe that the major characteristics of the spectra do reflect the doubly-charged ions formed in the source, the relative abundances of individual ions should be interpreted with some reservation.…”

Charge permutation reactions in tandem mass spectrometry

“…110,115,127 This reaction has been studied via tandem mass spectrometry with both reverse-and forward-geometry sector mass spectrometers by Beynon and co-workers 86 It has been demonstrated that isomeric compounds can be readily distinguished by comparing their 2E mass spectra, even if their singly charged ion mass spectra are identical. 131 Although most of the work has been carried out with small dictations, multiply charged macro-ions, including C 60 and related fullerene compounds, have been subjected to studies of this kind. 132,133 Models of charge distribution including charge motion on the ion microsurface of C 60 nC during the interaction trajectory have been proposed.…”

Charge stripping and E/2 mass spectra

“…of the singly charged parent ion, regardless of whether the actual process is (1) or (2). Where process (4) is a contributing factor the quoted mass is simply twice the actual mass (in a.m.u.)…”