The measurement of electron affinities by the gaseous electron capture technique

Abstract

Improvements of the gaseous electron capture technique for the measurement of absolute electron affinities of organic molecules are described. The dependence of the electron concentration on each of the parameters, pulse amplitude, pulse width, pulse interval, flow rate, and temperature is determined experimentally. Theoretical explanations for each of these dependences, except temperature, are given. The experimental results also lead to values of the drift velocity of electrons. Probable reaction schemes with and without an electron acceptor present are considered. Steady state concentrations of electrons are calculated in each case. The effect of the above parameters on the decrease in electron concentration in the presence of an electron acceptor is determined. Under these standardized conditions, the decrease in electron concentration is measured as a function of temperature. This measurement leads to a value of 0.57 ± 0.01 eV for the electron affinity of anthracene. Under our experimental conditions, the method does not yield electron affinity values for 9,10-anthraquinone or nitrobenzene.