Resonance structure in inelastic scattering of electrons from atomic hydrogen

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Abstract
Electron impact excitation of resonances between the principal quantum number n=2 and n=3 states of atomic hydrogen has been studied by observation of the radiation from the spontaneous decay of the 2p state and from the electric-field-quenched 2s state. Total excitation cross sections for the 2s and 2p states have been measured over the range from about 10.20 to 12.08 eV with an electron energy resolution estimated to be typically 9 meV. The 1P shape resonance just above 10.2 eV has been measured with better detail than previously and is located at 10.217+or-0.003 eV with a width of 22+or-3 meV. Several series of Feshbach resonances just below the n=3 threshold have been identified by observing states believed to be, sequentially, the 1S, 1D, 1P, 3F, 3D, 1S, 3P and 1D. The 3F state at 11.925 eV is dominant in both the 2s and 2p decay channels. Energies and widths are reported.