Emission spectroscopy of dipolar plasma source in low pressure hydrogen

International audience; Method of emission spectroscopy was used to study the plasmacharacteristics of the dipolar plasma source [1] in hydrogen at pressures 0.001 –0.01 Torr, microwave power 200-1200 W, microwave frequency 2.45 GHz.Spectral composition of plasma emission was investigated in the range of wavelength 601–627 nm. Functions of distributions over rotational (J=1–5) andvibrational (v=0–2) levels were determined for excited state d3П-u of hydrogenmolecules. Gas temperature Tg, rotational Trot(d3П-u) and vibrational Tv(X1+g)temperatures were determined on the basis of collisional-radiative models [2-4].It was found that the distribution function for the lower rotational levels ofH2(d3П-u) is Boltzmann distribution. Temperature Trot(d3П-u) changes in the range205–325 K. The distribution function for the lower vibrational levels of H2 in theexcited state d3П-u differs from the Boltzmann distribution. The magnitude of thevibrational temperature is 3100400 K, translational temperature is in the range420-650 K. The obtained values of Tg and Tv(X1+g) suggests that thedischarge at low pressures in hydrogen is an effective source of vibrationallyexcited hydrogen molecules.This study was supported in part by RFBR grant # 15-08-00070.