【作者】 王卫国；

【导师】 杨学锋； 徐勇；

【作者基本信息】 大连理工大学 ， 应用化学， 2007， 博士

【摘要】 分别利用阈值电离-分子束质谱技术和发射光谱技术，首次对介质阻挡放电氢等离子体中氢原子密度进行了定量研究；在低气压介质阻挡放电氢／氘等离子体中产生了高浓度长寿命的H₂^-／D₂^-离子，并对其进行了成功检测。本论文工作主要取得了以下结果：1．利用阈值电离-分子束质谱技术首次对介质阻挡放电氢等离子体中近极板区的氢原子密度进行了定量研究。首次提出了一种对分子束形成和质谱探测过程中产生的总质量歧视因子进行近似测定的方法，并应用于氢原子密度的定量研究。结果表明：在一定放电条件下（峰-峰值放电电压28 kV，频率24 kHz），当气压由2.0×133 Pa增加到14.0×133 Pa时，氢分子解离率由0.83％下降到0.14％。实验结果表明近极板区放电引起的气体温升可以忽略，则上述条件下相应的氢原子密度在（1.0～3.0）×10¹⁵atorns cm^-3范围内。2．利用发射光谱技术首次对介质阻挡放电氢等离子体放电区氢原子密度进行了定量研究。以氩为内标物，对放电区的氢分子解离率和氢原子密度进行了研究。结果表明：一定放电条件下（峰-峰值放电电压28 kV，频率24 kHz），当气压由2.0×133 Pa增加到38.0×133 Pa时，氢分子解离率由5.2％下降到0.1％，在14.0×133 Pa时的解离率约为0.3％。在忽略放电区气体温升的条件下，上述解离率对应的氢原子密度在（2.2～6.6）×10¹⁵ atoms cm^-3范围内。3．利用分子束质谱分别在低气压（～70 Pa）介质阻挡放电氢／氘等离子体中观测到了可靠的、高密度且长寿命的H₂^-／D₂^-离子。观测的H₂^-／H^-和D₂^-／D^-比值（～0.35-0.4）均比他人观测的结果高五个量级。利用排斥场电位技术测定了H₂^-和D₂^-离子的动能分布，由低能H₂^-和D₂^-离子的速度推算出它们各自寿命的上限分别大于40μs和55μs。4．分别利用阈值电离-分子束质谱和发射光谱技术对上述产生高密度H₂^-离子的放电体系中基电子态氢分子的振动、转动分布进行了诊断研究。质谱研究结果表明：近极板区氢分子的最大振动、转动量子数约为v=5，J=0或者v=0，J=19。利用发射光谱所测定的基电子态氢分子振动、转动温度分别约为2700 K和400 K。以上质谱和光谱数据说明该体系中并不存在亚稳态H₂^-高转动态模型所需的具高转动量子数的（如J=26）氢分子。在此基础上，讨论了长寿命H₂^-和D₂^-离子可能的形成机理。更多还原

【Abstract】 Atomic hydrogen density in dielectric barrier discharge hydrogen plasmas has been determined for the first time via threshold ionization-molecular beam mass spectrc,metry （TI-MBMS） and actinometric optical emission spectrometry （AOES）, respectively. Strong metastable H₂ and D₂ ions have been observed from low-pressure dielectric barrier discharge hydrogen and deuterium plasmas via molecular beam mass spectrometry and their possible formation mechanisms have been investigated. The main results presented in the dissertation have been summarized as followings:1. Atomic hydrogen density near the grounded electrode in dielectric barrier discharge hydrogen plasmas has been experimentally determined for the first time via TI-MBMS. A method has been proposed and performed for the first time to determine the total discrimination factor formed in the processes of beam formation and mass spectrometry measurement for the determination of atomic hydrogen density. It is shown that at certain discharge conditions （28 kV of peak-to-peak voltage, a.c. frequency of 24 kHz） the dissociation fraction of H₂ near the grounded electrode is decreased from 0.83% to 0.14% as the gas pressure increases from 2.0×133 Pa to 14.0×133 Pa. The gas temperature near the grounded electrode has been investigated experimentally and it is shown that the rise in gas temperature caused by the discharge can be ignored, so above H₂ dissociation fractions correspond to atomic hydrogen densities around 1.0-3.0×10¹⁵ atoms cm^-3.2. The dissociation fractions of H₂ and the atomic hydrogen density in the discharge volume of dielectric barrier discharge hydrogen plasmas has been experimentally determined via AOES using Ar as the actinometer. It is shown that at certain discharge condit.ions （28 kV of peak-to-peak voltage, a. c. frequency of 24 kHz） the dissociation fraction of H₂ in the plasma volume is decreased from 5.2% to 0.1% as the gas pressure increases from 2.0×133 Pa to 38.0×133 Pa. And if the rise in gas temperature also can be neglected, the corresponding atomic hydrogen densities are around 2.2～6.6×10¹⁵ atoms cm^-3.3. Strong and reliable mass signals of H₂^- and D₂^- ions with long lifetime have been experimentally observed from low-pressure dielectric barrier discharge hydrogen and deuterium plasmas via molecular beam mass spectrometry. The observed H₂^-/H^- and D₂^-/D^- ratios （～0.35-0.4） are over 5 orders of magnitude higher than those observed via other techniques. The kinetic energy of H₂^- and D₂^- ions sampled from the plasmas was determined to be widely distributed, from a few eV to＞100 eV, and their lifetime greater than～40μs for H₂^- ions and～55μs for D₂^- ions can be extracted from the velocity of those anions with low kinetic energy.4. The rovibrational distribution of H₂ in the electronic ground state has been determined in low-pressure H₂ plasmas where the strong mass signals of H₂^- ions are observed via TI-MBMS and OES. The highest rovibrational excitation states of H₂ in the electronic ground state has been determined to be about J=0, v=5 or J=19, v=0 via TI-MBMS. Using OES, the vibrational temperature and rotational temperature of the electronic ground state has been extracted to be 2700 K and 400 K, respectively. The possible formation mechanisms of H₂^- ions with further high J, required by the current high-rotation model, have been proposed and discussed.更多还原