Photoionization of Ethylene with Mass Analysis

Abstract

The photoionization‐efficiency curve of ethylene has been shown to have vibrational structure at the threshold for production of the first excited state of the parent ion. Autoionization of superexcited states in this region does not occur significantly. Appearance potentials were measured for the fragment ions C₂H₃⁺, C₂H₂⁺, and CH₂⁺. The thermochemical values obtained were $D_0\mathrm{°(}{\mathrm{C}}_2{\mathrm{H}}_3–\mathrm{H}\text{)\hspace{0.17em}=\hspace{0.17em}3.85}\mathrm{eV}{\mathrm{;\; D}}_0\mathrm{°(}{\mathrm{CH}}_2–{\mathrm{CH}}_2\text{)\hspace{0.17em}≤\hspace{0.17em}8.28}\mathrm{eV}\mathrm{;\; \Delta }{\mathrm{H}}_{\text{f0}}\mathrm{°(}{\mathrm{CH}}_2\text{)\hspace{0.17em}≤\hspace{0.17em}95.5}\mathrm{kcal}/\mathrm{mole}$ .