Structure in near threshold electron excitation of argon and neon

Excitation of the first excited levels of argon and neon have been observed around threshold. The experiment was carried out in a crossed-beam arrangement. An electron gun with energy width of less than 100 meV was used. The excitation was observed at 90 degrees . No correction for polarization has been applied. Resonance structure has been found. The structure is compared with structure found in transmission experiments and total cross section measurements for metastable excitation.