Research Papers in Physics and Astronomy


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Published in Physical Review A volume 13, number 16, 19 October 1964. Copyright © American Physical Society; used by permission.


Certain highly excited energy levels in helium have been observed optically and by inelastic electron scattering, and have been calculated theoretically. Reported here is the observation of these levels by the measurement of the energy spectrum of electrons emitted after bombardment with protons and hydrogen molecular ions. Some of the states show up clearly by this method which are weak or absent in the other techniques. Berry has previously observed autoionization of helium by this method, but his measurements lacked the resolution necessary to identify the states.

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