Eur. Phys. J. D 50, 257-264 (2008)
https://doi.org/10.1140/epjd/e2008-00232-x

Measurement of atomic hydrogen density in non-thermal H₂ plasmas via threshold ionisation-molecular beam mass spectrometry

¹ Laboratory of Plasma Physical Chemistry, P.O. Box 288, Dalian University of Technology, Dalian, P.R. China
² Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023, Dalian, P.R. China
³ State Key Laboratory of Material Modification by Ion, Electron and Laser Beams, Dalian University of Technology, Dalian, P.R. China

Corresponding authors: ^a yongxu@dlut.edu.cn - ^b hli@dicp.ac.cn

Received: 16 July 2008
Revised: 28 October 2008
Published online: 5 December 2008

Abstract

Determinations of radical density are essential to investigate the physical-chemical processes in plasmas and setup the related theoretical models. This paper presents the experimental measurement of atomic hydrogen near grounded electrode in dielectric barrier discharge medium-pressure hydrogen plasma via threshold ionisation-molecular beam mass spectrometry. After investigating the possible influences from parent molecules in excited states, background component and space-charge, evolution of atomic hydrogen density as functions of discharge parameters are investigated utilising the signal of H₂ molecule beam as the reference. At fixed gas pressure of 6.0 torr and a discharge voltage of 24 kV, atomic hydrogen density increases monotonously from 1.1×10¹⁴ to 2.0×10¹⁵ cm^-3 as the discharge frequency increases from 9 to 26 kHz. Similarly the rising discharge voltage also lead to enhancement of atomic hydrogen density.