Resonance in Elastic Scattering of Electrons by Helium Atoms

Les résonances dans les collisions atomiques. I. résonances élastiques électrons-atomes, électrons-molécules

“…Toutefois, McGowan [21] insiste sur le fait qu'en realite il existerait deux resonances tres proches l'une de 1'autre, la position de ces resonances correspondrait aux 6tats 1S et 3P de H sous le premier niveau excite (ls 2s) a 10,204 eV. L'6nergie de ces 6tats a ete calcul6e par la m6thode « close coupling » [23], [24], [25] [3], [15], [28], [29], [30], [31], [32], [33]. La premiere mesure [3] situait une resonance elastique a 19,3 eV :i: 0,1 eV, soit 0,5 eV en dessous du premier niveau excite de l'atome.…”

Electron-Atom Scattering: The State of the Experiments

“…This finding was consistent with the theoretical estimate of Wu [6] that the 1 ~2 s ' level of He-lies within a few tenths eV of the 23S energy, and with the fact that the 23S excitation crosssection computed by Massey and Moiseiwitsch [7] shows a sharp resonant peak at about 0.1 eV above threshold. It seems that Schulz was aware also of the preliminary results (eventually published in 1963) of Fleming and Higginson [8], who used an improved version of the Maier-Leibnitz transmission experiment in helium and found that the elastic scattering crosssection appears to have a minimum somewhere in the vicinity (their energy calibration was uncertain) of the 23S threshold energy. What Schulz found was a strong resonance below the 2jS threshold energy, and no marked behaviour at the threshold energy itself.…”