PHOTOIONIZATION OF HCN - ELECTRON AFFINITY AND HEAT OF FORMATION OF CN

A re-examination of the photoionization of HCN has revealed two processes, HCN+hν→H++CN-, and HCN+hv→H++CN+e, not previously reported. The difference in threshold values for the two processes leads directly to the electron affinity for CN, 3.82±0.02 eV. The threshold for the second process leads to ΔHf0°(CN) = 105.5±2 kcal/mole, but ΔHf0°(HCN) remains a major source of uncertainty. Copyright © 1969 by the American Institute of Physics.