Atomic and molecular spectra emitted by normal liquid ⁴He excited by corona discharge

The liquid ⁴He at fixed temperature 4.2 K and different pressures up to 8 MPa was excited by corona discharge of both negative and positive polarity. Emission of He I atomic lines and He₂ molecular bands are observed. In negative corona the lines spectra show a distinct blue-shift and line-broadening, which becomes stronger with the pressure increasing. The rotational structure of molecular bands is resolved at pressures (0.1–0.2) MPa. The blue shift of the Q-branch maximum at different pressures was observed. Rotational temperature of 900 K has been estimated for the d³Σ⁺u-b³Πg molecular band. A positive corona was realized on a point anode for fewer radii of the electrode and larger voltage than in the negative corona. Electric currents in both negative and positive corona differ weakly. Spectral analysis of the radiation from the positive corona shows qualitative differences of spectral features of these discharges. The spectra observed in the positive corona have marked nonsymmetric shape. The asymmetric atomic and molecular spectra show an increased intensity of their long-length (red) wings

Emission spectroscopy of dipolar plasma source in low pressure hydrogen

International audienceMethod 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 3100400 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

Study of the vibrational distribution function of the hydrogen molecule in the ground state X1Sigma+g in gas discharges

International audienceThe comparison of the vibrational distribution functions obtained by experimentaltechniques and numerical simulation in the different discharges was carried out.There are considered and discussed different sets of level – to – level ratecoefficients at which a good agreement is observed between theory andexperiment

Experimental and numerical simulation of the vibrational distribution function of the hydrogen molecule in the ground state X1Σ+g in gas discharges

International audienceThe comparison of the vibrational distribution functions obtained by experimental techniques andnumerical simulation in the different discharges was carried out. There are considered and discusseddifferent sets of level – to – level rate coefficients at which a good agreement is observed between theoryand experiment

Experimental and numerical simulation of the vibrational distribution function of the hydrogen molecule in the ground state X1Σ+g in gas discharges

International audienceThe comparison of the vibrational distribution functions obtained by experimental techniques andnumerical simulation in the different discharges was carried out. There are considered and discusseddifferent sets of level – to – level rate coefficients at which a good agreement is observed between theoryand experiment

Kinetics of electron states of hydrogen molecules in nonequilibrium discharges: Singlet states

International audienceThis study continues previous publications devoted to kinetic processes in nonequilibrium hydrogen plasma. This review contains an analysis of the kinetics of hydrogen molecules in the ground state and in excited singlet electron states in various gas discharges. The distribution functions measured over the vibrational levels of a hydrogen molecule in the ground electron state are compared with those calculated within the developed level semiempirical collisional-radiative model of low-temperature hydrogen plasma. A database of the measured and calculated collisional-radiative characteristics of kinetic processes involving excited hydrogen molecules and the parameters of low-temperature hydrogen plasma is formed

Spectroscopic study of the negative corona discharge in liquid and supercritical 4He

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