The mechanism of extraordinary broadening of the Balmer lines of hydrogen admixed with noble gases in a dc glow discharge and a capacitively coupled rf discharge is studied over a wide range of pressure and gas compositions to test the field acceleration model (Cvetanovic et al 2005 J. Appl. Phys. 97 033302). High-resolution optical emission spectroscopy is performed parallel to the electrode axis (end-on) and perpendicular to the electrode axis (side-on) along with Langmuir probe measurements of plasma density and electron temperature for the parallel plate rf capacitive discharge case. Sharp pin-shaped tungsten dc electrodes are also used to minimize the backscattering of ions that are theorized by a field acceleration model to be heated in the sheath region. An excessively broad and symmetric (Gaussian) Balmer emission line corresponding to 20–60 eV of hydrogen atom energy is observed in Ar/H₂ and He/H₂ plasmas when compared with the majority species atom temperatures. Energy is transferred selectively to hydrogen atoms whereas the atoms of admixed He and Ar gases remain cold (<0.5 eV). Since there is neither a preferred ion nor atom in the field acceleration model, one should also observe enhanced temperature hydrogen and helium atoms in He/H₂ discharges where the atomic mass is more comparable (4 : 1).