BOUND EXCITED-STATES OF CHLOROETHYLENE ANIONS STUDIED BY ELECTRON-CAPTURE NEGATIVE-ION MASS-SPECTROMETRY

Electron detachment from the ground state of negative ions of chloroethylenes and dissociation from a bound excited state have been simultaneously observed by measuring the temperature dependence of [Cl-]/[M-] in a thermal electron attachment chemical ionization mass spectrometer source. The data show two slopes in a typical reciprocal temperature plot. The lower slope is the difference in activation energies for attachment to the two negative ion states, and the higher slope gives the detachment energy from the ground state. The detachment energy for C2Cl4- is 0.5 eV while that for C2HCl3- is 0.3 eV. The differences in the activation energies for thermal electron attachment are 0.1 eV for both molecules.