Fragment Ions from CH3CHO and (CH3)2CO by Electron Impact

Abstract

The ionization‐efficiency curves for the parent and fragment ions from CH₃CHO and (CH₃)₂CO have been examined by the second differential method. The appearance potentials for CH₃CO⁺, namely, 10.2±0.1 eV [(CH₃)₂CO] and 10.5±0.2 eV (CH₃CHO), are much lower than previously accepted electron‐impact values. Apart from CO⁺(CH₃CHO) no appearance potentials can be easily obtained for any of the other fragment ions. No kinetic energy was found for the light ion CH₃⁺, nor the heavier ions CO⁺, HCO⁺(CH₃CHO), and CH₃CO⁺[(CH₃)₂CO].