Theoretical Calculations of Mass Spectra: Fragmentation of C6–C8 Alkane Ions

An improved statistical theory of mass spectra is here applied to the fragmentation of five alkanes: n-hexane, 2-methylpentane, 3-methylpentane, n-heptane, and n-octane. The calculated breakdown curves are compared with the experimental curves obtained from photoionization studies by Steiner, Geise, and Inghram. The major fragmentations, the metastable ions, and the ``missing metastable'' ions are computed for gas temperatures of 0° and 300°K. The improved quasiequilibrium theory yields satisfactory breakdown curves for the above molecules using physically reasonable activated complexes and activation energies, and without requiring introduction of artificial parameters such as an ``effective number of oscillators.''