Threshold Electron Excitation of Auger-Electron and X-Ray Emissions in La

摘要

The intensities of the M sub 5 O sub 3 and M sub 5 N sub 3 characteristic X-ray lines and the M sub 5 N sub 4 , sub 5 N sub 4 , sub 5 Auger-electron line from La were measured as functions of the electron excitation energy near the M sub 5 ionization energy. The excitation curve of each of these emissions contains a line-like structure a few eV above the threshold. The full width at half maximum (3.0 +- 0.2 eV) and relative height (4x) of this structure are the same in these three excitation curves; however, they are different than the respective values (2.3 +- 0.2 eV and 200x) we previously measured for a resonant bremsstrahlung emission observed when the electron excitation energy was near the M sub 5 ionization energy. These results support our earlier proposal that two distinct states are excited for near threshold, electron excitation of the La M sub 5 level: the 3d exp 9 4f exp 0 state which decays via the M sub 5 series characteristic X-ray and Auger-electron emissions, and the 3d exp 9 4f exp 2 intermediate bound state which appears to decay by only a single channel - the emission of a resonant X ray with a photon energy of 832 +- 1 eV. These results may be evidence of a closed channel resonance in the electron scattering cross section in solid La, similar to resonances found in Ne gas. (ERA citation 08:057800)