Diagnosis Of H₃^-/D₃^- Anions And OH Radicals In Non-Thermal Equilibrium Plasmas

Molecular-beam mass spectrometry (MBMS) and emission spectroscopy techniqueshave been used respectively to diagnose the H₃^-/D₃^- anions in hydrogen plasmas producedby dielectric barrier discharges and the OH radicals generated by pulsed corona discharge.The main results presented in the dissertation have been summarized as follows:1. H₃^- anions produced by pure hydrogen dielectric barrier discharges have beendiagnosed by the molecular beam mass spectrometry (MBMS) at gas pressure from 1.5to 7.6 Torr. The stability of H₃^- anions is further demonstrated experimentally by theexperiments using hydrogen's isotope deuterium. The signal intensity rate of H₃^-/H^- ishigher than that of the controversial experimental results reported earlier by six ordersof magnitude, and the lifetimes of the H₃^- and D₃^- anions observed in our experimentsare greater than 50μs and 70μs respectively. The possible mechanism of forming H₃^-anions by three-body collisions (H^-+ H₂ + M→H₃^-+ M) is proposed for the first time. The observed results confirmed the stability of H₃^-. The consistent conclusion of the stability of H₃^- anions in theory and experiment is obtained.The effects of gas pressure and discharge parameters on the ion currents of H₃^-/H^-have been investigated. The observed ion current of H^- is one to several orders of magnitude higher than that of H₃^- at gas pressure from 1.5 to 7.6 Torr at 40 kV peak-peak discharge voltage and 35 kHz discharge frequency. Only H^- ion signal is observed at gas pressure from 7.7 to 60 Torr. The ion current of H^- increases with the increasing of discharge peak voltage and discharge frequency, and exhibits a maximum over the studied range of gas pressure.The effects of gas pressure, discharge peak voltage, and discharge frequency on the ion currents of positive ions (H⁺, H₂⁺, and H₃⁺) in cathode sheath region produced by dielectric barrier discharge hydrogen plasmas have been also investigated at gas pressure from 1.0 to 80 Torr.2. The emission spectra of OH(A²âˆ‘→X²Î , 0-0), O(3p⁵P→3s⁵S₂⁰) and H(n=3-2) produced by the positive pulsed corona discharge of N₂ and H₂O mixture in a needle-plate reactor have been successfully recorded against a severe electromagnetic interference coming from the pulsed corona discharge at one atmosphere. The relative populations and the vibrational temperature of N₂ (C, v') were determined with the corresponding Franck-Condon factor and the emission intensities of theΔv=-3 andΔv=-4 vibration transition band of N₂ (C³Î _u→B³Î _g). The emission intensity of OH (A²âˆ‘→X²Î 0-0) can be obtained by subtracting the emission intensity of theΔv = +1 vibration transition band of N₂ (C³Î _u→B³Î _g) from the overlapping spectra. The relative populations of OH (A²âˆ‘) and O(3p⁵P) have been obtained by the emission intensity of OH and O and the corresponding Einstein's transition probabilities. The effects of pulsed peak voltage, pulsed repetition rate, and oxygen flow on the emission intensities of OH (A²âˆ‘→X²Î 0-0), O(3p⁵P→3s⁵S₂⁰ 777.4 nm), H (n=3-2 656.3 nm) and the relative populations of OH (A 2) and O(3p P) are investigated.It is found that when the pulsed peak voltage and the pulsed repetition rate are increased, the emission intensities of OH (A²âˆ‘→X²Î 0-0), O (3p⁵P→3s⁵S₂⁰ 777.4 nm), and H (n=3-2 656.3 nm) enhance correspondingly. The emission intensities of O (3p⁵P→3s⁵S₂⁰ 777.4 nm) and H (n=3-2 656.3 nm) increase with the flow rate of oxygen (from 0 to 30 ml/min) and achieve a maximum value at flow rate of 30 ml/min. When the flow rate of oxygen is increased further, the intensities decrease obviously. The emission intensity of OH (A²âˆ‘→X²Î 0-0) decreases with the flow rate of oxygen. When the flow rate of oxygen increases from 0 to 30 ml/min, the relative population of O (3p⁵P) active atom increases and achieve a maximum value at flow rate of 30 ml/min. When the flow rate of oxygen is increased further, the relative population of O(3p⁵P) active atoms decreases obviously. And the relative population of OH(A²âˆ‘) radical decreases nonlinearly with the flow rate of oxygen.3. The emission spectra of OH (A²âˆ‘→X²Î 0-0) and N₂(C³Î _u→B³Î _g) produced by the bi-directional pulsed corona discharge of N₂ and H₂O mixture in a wire-plate reactor have been successfully recorded at one atmosphere. The relative populations and the vibrational temperature of N₂ (C, v') and the emission intensity of OH (A²âˆ‘→X²Î 0-0) are determined. The effects of pulsed peak voltage, pulsed repetition rate, and oxygen flow on the emission intensity of OH (A²âˆ‘→X²Î 0-0) and the relative population of OH (A²âˆ‘) are investigated. It is found that the emission intensity of OH (A²âˆ‘→X²Î 0-0) enhance correspondingly with increasing the pulsed peak voltage and the pulsed repetition rate. The relative population of OH (A²âˆ‘) rises linearly with increasing the pulsed peak voltage and the pulsed repetition rate. When the oxygen is added in N₂ and H₂O mixture gas, the emission intensity of the OH (A²âˆ‘→X²Î 0-0) decreases rapidly. The relative population of OH (A²âˆ‘) radical decreases exponentially with increasing the added the flow rate of oxygen.