Research Papers in Physics and Astronomy


Date of this Version

April 1981


Published in Phys. Rev. A 23, 1745 - 1760 (1981) [Issue 4 – April 1981]. ©1981 The American Physical Society. Used by permission.


We have measured the beam-foil collision-induced alignment of the 3p 1P, 3p 3P, 3d 1D, and 3d 3D states of He I for He+ beam energies between 30 and 1300 keV. The alignment of all four states is found to vary with beam-current density as well as energy. The number of secondary electrons emitted per incident ion, γ, has also been measured as a function of foil temperature and beam energy between 400 and 1400 keV. The rate of change of both alignment and γ with foil temperature exhibits a general correlation. The energy dependence of alignment may be understood in terms of simple impact-excitation collisions. We also discuss our results in terms of the Kupfer-Winter surface electric-field model. The interaction between atoms emerging from the foil and slow secondary electrons is considered.

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