Low-energy (≲3 eV) electron attachment to molecules in very-high pressure gases: C2H5Br

Abstract

Significant changes have been observed in both the magnitude and the energy dependence of the rate of attachment of slow (≲3 eV) electrons to bromoethane (C₂H₅Br) in either N₂ or Ar gases with increasing density of these media from 500 to 25 000 Torr for N₂ and from 500 to 42 000 Torr for Ar. The observed density and energy dependences of the attachment rates are discussed on the basis of two plausible reaction schemes involving either one or two states of C₂H₅Br⁻. On the basis of the one‐state reaction scheme, determinations were made of the absolute rate of formation of C₂H₅Br⁻* and of the relative magnitudes of the rates for dissociation and autoionization of the metastable C₂H₅Br⁻* ion as a function of the mean electron energy 〈ε〉. On the basis of the same reaction scheme, the lifetime of C₂H₅Br⁻* was estimated to be ?13 psec in the mean energy range 0.3–1 eV. Although the vertical attachment energy for the C₂H₅Br molecule is ∼0.75 eV, the present results imply that its adiabatic electron affinity is positive (≳0 eV).