Nature of the Light Emission by Hydrogen Ions†

Abstract

ABSTRACT Light produced by positive ion beams in their parent gas consists of undisplaced broadened lines originating from atoms with thermal velocity and displaced lines forming the Doppler band from atoms with velocity components parallel to the beam. The intensity distribution in the Doppler band shows maxima which correspond to beam velocities of the various ion species. A region of zero intensity exists between an undisplaced line and the red end of the associated Doppler band. A study of the Doppler band gives the clue to the emission process which— it is suggested—is caused by charge transfer collisions leading to dissociation of a ‘ compound molecule ’, one of the dissociation products being an excited atom. An estimate is made of the average cross section in hydrogen which produces the observed photographic density of the spectrogram. This gives a maximum value of  10−19 cm2, which is of the same order of magnitude as the excitation cross section of positive ions in their parent gas. From the po...