Metastable Transitions in Mass Spectra of Methane and the Deuteromethanes

Abstract

The mass spectra of methane and the deuteromethanes have been carefully studied to determine whether any parent‐ion metastable transitions occur. The only transition found is CD₄⁺→CD₃⁺+D. All other species yield only collision‐induced dissociations. Approximate appearance‐potential studies indicate that this transition occurs from the CD₄⁺ ion in the group of lowest‐lying electronic levels which are produced by Jahn—Teller splitting of the nominally degenerate ground state. Some implications of this unusual isotope effect are discussed.