Electron attachment to cyclic anhydrides and related compounds

Negative ion production cross section are sections are tabulated as a function of the bombarding electron energy for dissociative and nondissociative electron attachment to various cyclic anhydrides and related compounds. The unsaturated compounds, maleic anhydride (250 μsec), phthalic anhydride (313 μsec), pyromellitic anydride (8000 μsec), and maleimide (43 μsec) attach thermal electrons to form parent negative ions which are metastable with autodetachment lifetimes that decrease with an increase in the energy of the bombarding electron. The number in parentheses following each compound is the lifetime at peak cross section. Compound negative ion states are reported for the saturated compounds succinic anhydride (1.3 eV), cyclobutane‐dicarboxylic anhydride (1.3 eV), glutaric anhydride (0.6 eV), and succinimide (1.1 eV) for electron energies given in the parentheses. In most of the anhydrides the most abundant anions produced by dissociatve electron attachment are metastable ${\mathrm{RCO}}_2^{‐}*$ ions which result from the ejection of neutral CO from the parent molecules. Experimental evidence shows that the ${\mathrm{RCO}}_2^{‐}$ dissociates following autodetachment. The metastability of an observed ${\mathrm{CO}}_2^{‐}*$ ion is attributed to poor Franck‐Condon overlap between the potential energy surface of CO₂ and ${\mathrm{CO}}_2^{‐}$ . Negative ion mass spectra are included for acetic anhydride and acetyl peroxide.