The absorption of radiation originating from a beam of electrons in helium: A note on the electron excitation function for the sharp series of orthohelium

Abstract

1. (1) The present work substantiates the results of previous experiments which show that absorption can take place in excited helium not only from the 2S and 2s metastable levels but also from the non-metastable 2P and 2p states. The absorption for higher series members than has hitherto been reported is also proved. 2. (2) The previous determined fact that the diffuse series lines are more easily absorbed than the sharp series has now been found to hold for higher terms of these series. 3. (3) The region in close vicinity to an electron beam in helium contains a relatively large number of excited atoms in both metastable and non-metastable states, capable of producing absorption.