title: Determination of atomic hydrogen in non-thermal hydrogen plasmas by means of molecular beam threshold ionization mass spectrometry.
abstract: Atomic hydrogen plays important roles in chemical vapor deposition of functional materials, plasma etching and new approaches to chemical synthesis of hydrogen-containing compounds. The present work reports experimental determinations of atomic hydrogen near the grounded electrode in medium-pressure dielectric barrier discharge hydrogen plasmas by means of molecular beam threshold ionization mass spectrometry (MB-TIMS). At certain discharge conditions (a.c. frequency of 24 kHz, 28 kV of peak-to-peak voltage), the measured hydrogen dissociation fraction is decreased from approximately 0.83% to approximately 0.14% as the hydrogen pressure increases from 2.0 to 14.0 Torr. A simulation method for extraction of the approximate electron beam energy distribution function in the mass spectrometer ionizer and a semi-quantitative approach to calibrate the mass discrimination effect caused by the supersonic beam formation and the mass spectrometer measurement are reported.
authors.affiliation: Laboratory of Plasma Physical Chemistry, Dalian University of Technology, Dalian, China.
authors.forename: Wei-Guo
authors.initials: WG
authors.lastname: Wang
authors.forename: Yong
authors.initials: Y
authors.lastname: Xu
authors.forename: Xue-Feng
authors.initials: XF
authors.lastname: Yang
authors.forename: Wen-Chun
authors.initials: WC
authors.lastname: Wang
authors.forename: Ai-Min
authors.initials: AM
authors.lastname: Zhu