Mass-Spectrometric Study of Photoionization. VIII. Dicyanogen and the Cyanogen Halides

Abstract

Photoionization-yield curves are obtained for the molecule and selected radical ions of C2N2, FCN, ClCN, BrCN, and ICN from threshold to 600 Å. Vibrationally excited states of ions and autoionization of Rydberg levels in the molecules are observed and discussed briefly. The X+ ion thresholds in the heavier cyanogen halides are used to obtain: ΔHf0o (CN) = 101.5 kcal mole−1, ΔHf0o (CN+) = 430.0 kcal mole−1, and I (CN) = 14.2 eV. These are applied to compute ΔHf0o (FCN) = 5.6 kcal mole−1, D (F–CN) = 5.0 eV, I (C2) = 12.15 eV, and other thermodynamic properties. The formation of CN+ from dicyanogen apparently includes about 0.6 eV excess energy near the threshold.