A study of the line shapes of hydrogen Balmer series lines in RF generated low pressure He/H(2) plasmas produced results suggesting a catalytic process between helium and hydrogen species results in the generation of 'hot' (ca. 28 eV) atomic hydrogen. Even far from the electrodes 'hot' atomic hydrogen was predominant in He/H2 plasmas. Line shapes, relative line areas of cold and hot atomic hydrogen (hot/cold > 2.5), were very similar for areas between the electrodes and far from the electrodes for these plasmas. In contrast, in Xe/H(2) only 'warm' (<5 eV) hydrogen (warm/cold < 1.0) was found between the electrodes, and only cold hydrogen away from the electrodes. Earlier postulates that preferential hydrogen line broadening in plasmas results from the acceleration of ionic hydrogen in the vicinity of electrodes, and the special charge exchange characteristics of Ar/H(2)+ are clearly belied by the present results that show atomic hydrogen line shape are similar for He/H2 plasmas throughout the relatively large cylindrical (14 cm ID x 36 cm length) cavity. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved