Spectroscopic Observation of Translational–Rotational Nonequilibrium in Low-Density Hydrogen Plasma Flow

摘要

Translational–rotational nonequilibrium of low-density hydrogen plasma flow was investigated using emissionnspectroscopy. The translational temperature can be determined by BalmerHu0001 line profile fitting, taking into accountninstrumental broadening, Doppler broadening, and spin-orbit coupling, when natural, Stark, and Zeemannbroadenings are less dominant. The rotational temperature can be determined by the line intensity fitting of thenFulcher-u0002 band. This emission spectroscopic method was experimentally applied to our low-density inductivelyncoupled plasma wind tunnel. Spectroscopicmeasurements of the flow behind the shock wave over a blunt body werenconducted.TheKnudsen numberwas on the order of 0.1, and the translational–rotational relaxation timewas largernthan the flow characteristic time. The nonequilibrium between the translational and rotational modes wasnsuccessfully observed using our spectroscopicmethod. The experimental results qualitatively agreed with numericalnsimulation results.