Comparison of excessive Balmer α line broadening of inductively and capacitively coupled RF, microwave, and glow-discharge hydrogen plasmas with certain catalysts

From the width of the 656.3-nm Balmer α line emitted from inductively and capacitively coupled radio frequency (RF), microwave, and glow-discharge plasmas, it was found that inductively coupled RF helium-hydrogen and argon-hydrogen plasmas showed extraordinary broadening corresponding to an average hydrogen atom energy of 250-310 and 180-230 eV, respectively, compared to 30-40 and 50-60 eV, respectively, for the corresponding capacitively coupled plasmas. Microwave helium-hydrogen and argon-hydrogen plasmas showed significant broadening corresponding to an average hydrogen atom energy of 180-210 and 110-130 eV, respectively. The corresponding results from the glow-discharge plasmas were 33-38 and 30-35 eV, respectively, compared to ≈ 4 eV for plasmas of pure hydrogen, neon-hydrogen, and xenon-hydrogen maintained in any of the sources. Similarly, the average electron temperatures T_e for helium-hydrogen and argon-hydrogen inductively coupled RF and microwave plasmas were high (43 200 ± 5% K, 18 600 ± 5% K, 30 500 ± 5% K, and 13 700 ± 5% K, respectively); compared to 9300 ± 5% K, 7300 ± 5% K, 8000 ± 5% K, and 6700 ± 5% K for the corresponding plasmas of xenon-hydrogen and hydrogen alone, respectively. Stark broadening or acceleration of charged species due to high electric fields cannot explain the inductively coupled RF and microwave results since the electron density was low and no high field was present. Rather, a resonant energy transfer mechanism is proposed.