Excitation of optically forbidden transitions in argon and neon by electron impact

A radial electron monochromator and analyser system employing several new features has been used to study low energy differential inelastic electron scattering by ground state argon and neon atoms. Angular distributions for a number of optically inaccessible states are reported at energies between 30 and 100 eV and over a range of scattering angles from 0–90°. In particular, results are shown for the metastable states (³P₂, ³P₀) of argon as well as for various J levels in the parity forbidden bands (ns²np⁶ → ns²np⁵(n + 1)p) for argon and neon.