Spectroscopic optimization of abnormal glow conditions for plasma ion nitriding A. Qayyum, R. Ahmad, A. Waheed and M. Zakaullah Eur. Phys. J. Appl. Phys., 32 1 (2005) 45-52 Published online: 15 September 2005 DOI: 10.1051/epjap:2005064