Negative ion properties of fluoranil, chloranil, and bromanil: Electron affinities

Bound and excited negative ion states of p-fluoranil (FA), p-chloranil (CA), and p-bromanil (BA) are studied from experiments involving collisions of electrons, Na, K, and Cs beams with FA, CA, AND BA. Reaction thresholds for producing FA−, CA−, and BA− are determined as a function of the temperature of the target molecules. The electron affinities corresponding to 0 °K were measured to be 2.92±0.2 eV for FA, 2.76±0.2 eV for CA, and 2.44±0.2 eV for BA. FA, CA, and BA attach ∼ 0 eV electrons and FA attaches 0.5 eV electrons to form metastable parent negative ions with lifetimes in the millisecond range. These lifetimes are a function of the electron energy. Dissociative and nondissociative resonances observed via electron attachment to p-benzoquinone (PBQ) and the ’’anils’’ are correlated with the optically determined 2B3g′, 2B1u, and 2Au states of PBQ− and the anion radicals of several substituted quinones.