Dissociative electron attachment to the volatile anaesthetics enflurane and isoflurane and the chlorinated ethanes pentachloroethane and hexachloroethane

Negative ion formation through dissociative electron attachment to the gas-phase volatile anaesthetics enflurane and isoflurane (C₃H₂ClF₅O) and to two chlorinated ethanes, pentachloroethane (C₂HCl₅) and hexachloroethane (C₂Cl₆), have been studied in a crossed electron-molecular beam two sector field mass spectrometer experiment. Anion efficiency curves for the negatively charged fragments have been measured over an electron energy range of approximately 0-17 eV, with an energy resolution of ∼1 eV. For the chlorinated ethanes, resonance features were generally found at ∼0 eV and at 7.5 eV. For the volatile anaesthetics, no zero energy resonances were observed. Instead, product anions were detected mainly in the 2-3 eV and 9 eV energy regions, with the exception of Cl^-, whose dominant resonance occurs at approximately 0.6 eV and 0.9 eV for isoflurane and enflurane, respectively. To aid in the interpretation of the experimental results, quantum chemical calculations providing thermochemical thresholds of anion formation are also presented.