Metastable Ions and Isotope Effects in the Mass Spectra of Propane and Deuterated Propanes

Abstract

Metastable transitions occurring in the mass spectrum of C₃H₈, CH₃CD₂CH₃, CD₃CH₂CD₃, and C₃D₈ have been investigated by means of the defocusing technique using a double‐focusing mass spectrometer. In addition, detailed calculations of the decomposition of propane ions have been carried out, using the quasiequilibrium theory of mass spectra. Very strong isotope effects are observed and are accounted for quantitatively, and it is concluded that the quasiequilibrium theory provides an adequate framework for the description of both metastable ions and the general fragmentation processes responsible for the mass spectra of the deuterated propanes.