Electron-capture detector and multiple negative ions of aromatic hydrocarbons

Multiple electron affinities are identified in the temperature dependence of the electron-capture detector: naphthalene, 0.16, 0.13+/-0.01, anthracene, 0.69, 0.60, 0 53+/-0.01; tetracene 1.1, 0.88+/-0.03, 0.53+/-0.05; pyrene, 0.61, 0.50+/-0.02; azulene 0.90, 0.80, 0.70+/-0.02, 0.65, 0.55+/-0.05; acenaphthylene, 0.80, 0.69, 0.60, 0.50+/-0.05; and c-C8H8, 0.80, 0.70, 0.55+/-0.02; (all in eV). These are obtained from a rigorous least squares procedure incorporating literature values and uncertainties. The adiabatic electron affinities for about 40 hydrocarbons listed in the US National Institute of Standards and Technology (NIST) tables are evaluated. The adiabatic electron affinity values not listed in NIST are biphenylene, 0.45+/-0.05 eV and coronene. 0.8+/-0.05 eV. Morse potential energy curves in the C-H dimensions illustrate multiple states for benzene and naphthalene.