MOBILITIES OF RADICAL CATIONS AND ANIONS, DIMER RADICAL-ANIONS, AND RELATIVE ELECTRON-AFFINITIES BY TIMES OF FLIGHT IN N-HEXANE

The mobilities of several radical cations and anions are measured in n -hexane using a thin-sheet time-of-flight (TOF) technique. We observe the radical cations of N,N,N,N'-tetramethyl-p-phenylenediamine, zinc t etraphenylporphine, and pyrene and the radical anions of perfluorobenz ene, p-benzoquinone, anthraquinone, chloranil, buckminsterfullerene (C -60), and octafluoronaphthalene: For all electron accepters but C-60,, the dependence of the anionic TOF on acceptor concentration reveals t he:appearance of the homodimer radical anion at sufficiently high conc entrations. The equilibrium constant for the monomer anion/monomer acc eptor association reaction is obtained from the concentration studies. A Born-Haber cycle is then applied to estimate the difference between the electron affinities of the monomer and dimer molecules in the gas phase.