Electron impact excitation of metastable states of benzene, toluene, and aniline

Abstract

Electron impact excitation functions for the formation of metastable states of benzene, toluene, and aniline are measured under low pressure conditions (∼1 × 10−5 torr) with an electron energy resolution of 0.3 eV. Considerable evidence is presented for assigning these metastables as the lowest triplet states T1. Each excitation function exhibits several features at low electron energy (4–15 eV), which are interpreted in terms of resonances which decay to give T1 and nonresonant exchange excitation processes. Comparison of these triplet excitation functions with the optical excitation functions for fluorescence (see the preceding paper) indicates that intersystem crossing does not make a major contribution to T1 formation under the present experimental conditions. From time-of-flight measurements a lower limit of 500 μsec is estimated for the lifetime of the lowest triplet state T1 for these three molecules.