Isotope dependence of the breakdown strength of gases

It was found that while the highly nonuniform direct current breakdown voltages, V-sub s/, of H2 and NH3 exceed, respectively, those of D2 and ND3, the V/sub s/ of CH4 is substantially lower than that of CD4. The former isotope effect may be attributed to the higher ionization coefficients for the deuterated species compared with the nondeuterated, and the latter isotope effect may result from differences in the electron impact induced dissociation processes of the isotopic pairs of molecules.