Molecular Ions in Radiation Chemistry. I. Formation of Aromatic-Amine Cations in CCl4 by Resonance Charge Transfer at 77°K

Abstract

Gamma-irradiated polycrystalline CCl4 at 77°K provides evidence that positive charge migrates and is trapped by the matrix itself. The trapped positive hole absorbs at about λmax=400 mμ in pure CCl4 or dilute solid solutions of aromatic amines. The solvent band is depressed by aromatic amines or other additives which act as hole traps with appearance of the corresponding amine cation absorption. After γ irradiation the residual 400-mμ band photobleaches at 77°K with increase in solute cation absorption. Brief heating to 143°K gives the same result. A kinetic treatment which assumes that the only labile species in the system is migrating positive charge can explain the experimental results in a satisfactory way. The kinetic analysis gives a rough estimate of total available positive charge created per 100 eV of absorbed energy as 1.9. Several aromatic amines have been used as test substances and their optical absorption spectra recorded.