Neon K-shell excitation studied by electron energy-loss spectroscopy

The electron energy-loss spectrum of gaseous neon in the region of 1s (K-shell) excitation has been investigated using small-angle inelastic scattering of 2.5 keV electrons. The spectrum is compared with previous optical studies of Ne 1s excitation. Term values are in reasonable agreement with those for the equivalent core atom, sodium. In addition to the optically allowed 1s to np series, the optically forbidden 1s to 3s electric quadrupole transition has been observed at 865.1 eV. Values for the Ne 1s ionisation potential (870.09 eV) and an upper bound to the natural linewidth of the 1s to 3p transition (0.31 eV) have been derived.