Comparison of excessive Balmer α line broadening of glow discharge and microwave hydrogen plasmas with certain catalysts

• Published in: Journal of applied physics 2002-12, Vol.92 (12), p.7008-7021
• Main Authors: Mills, R. L., Ray, P. C., Dhandapani, B., Mayo, R. M., He, J.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.1522483

From the width of the 656.3 nm Balmer α line emitted from microwave and glow discharge plasmas, it was found that a strontium–hydrogen microwave plasma showed a broadening similar to that observed in the glow discharge cell of 27–33 eV; whereas, in both sources, no broadening was observed for magnesium–hydrogen. Microwave helium–hydrogen and argon–hydrogen plasmas showed extraordinary broadening corresponding to an average hydrogen atom temperature of 180–210 eV and 110–130 eV, respectively. The corresponding results from the glow discharge plasmas were 33–38 eV and 30–35 eV respectively, compared to ≈4 eV for plasmas of pure hydrogen, neon–hydrogen, krypton–hydrogen, and xenon–hydrogen maintained in either source. Similarly, the average electron temperature Te for helium–hydrogen and argon–hydrogen microwave plasmas were high, 30 500±5% K and 13 700±5% K, respectively; compared to 7400±5% K and 5700±5% K for helium and argon alone, respectively. External Stark broadening or acceleration of charged species due to high fields can not explain the microwave results since no high field was present, and the electron density was orders of magnitude too low for the corresponding Stark effect. Rather, a resonant energy transfer mechanism is proposed.