Excitation kinetics of electronic states of hydrogen molecules in nonequilibrium discharges: Electronic ground state

International audienceThis review offers an analysis of the vibrational kinetics of hydrogen molecules in the singlet ground state X 1∑ g + for various gas discharges. The measured quasi-stationary vibrational-level distribution functions of a hydrogen molecule in the electronic ground state at the corresponding vibrational temperatures of the first level and those calculated in the framework of a semiempirical level collisional–radiative model of low-temperature plasma in hydrogen, developed in this study, are compared. A database of the measured and calculated characteristics of kinetic processes involving vibrational-excited hydrogen molecules, as well as macro and microparameters of hydrogen low-temperature plasma, is created

Optical emission spectroscopy and modeling of plasma produced by excimer laser ablation of titanium oxides

In the present study, the time evolution of electron number density, of electron, atom and ion temperatures, of plasma produced by KrF excimer laser ablation of titanium dioxide and monoxide targets, are investigated by temporally and spatially resolved optical emission spectroscopy over a wide range of laser fluence from 1.7 to 6 J cm-2, oxygen pressures of 10-2-10-1 torr and in a vacuum. A state-to-state collisional radiative model is proposed for the first time to interpret the experimental results at a distance of 0.6 mm from the target surface, in vacuum and for a time delay from 100 to 300 ns from the beginning of the laser pulse. In particular, we concentrate our attention on problems concerning the existence of the local thermodynamic conditions in the laser-induced plasma and deviation from them, as observed in our experiment. The numerical model proposed for calculating the electron number density and the population densities of atoms and ions in excited states give good quantitative agreement with the experimental results of the optical emission spectroscopy measurements

Theoretical and experimental CARS rotational distributions of H

Multiplex coherent anti-Stokes Raman scattering (CARS) spectroscopy is used for thermometry in H2 radio-frequency capacitive discharge plasma at low gas temperature of 300-400 K, pressure of 0.4-4 Torr and power of 100 W. Results of the investigation of population densities of rotational levels in the ground electronic state of the hydrogen molecule and measurements of rotational temperature by multiplex H2 CARS spectroscopy in H2 radio-frequency capacitive discharge plasma are reported. Computational codes have been realized to determine the rotational and vibrational temperature and to analyze H2 CARS spectrum for equilibrium and non-equilibrium conditions. To ensure the reliability of the rotational temperature measurements, we also apply method of scanning narrow-band CARS spectroscopy in our investigations

Spectroscopic investigations of corona discharge in high pressure helium at 300 K

Gaseous Helium at 300 K and pressure (0.1–3) MPa was excited using a corona discharge both for negative and positive high voltages. The light emitted from the ionization zone of the discharge was analyzed. Asymmetric shape of atomic lines 706 nm and 728 nm was recorded. Blue wings of the lines are more intensive than their red wings. The line shape is described as a convolution of Lorentz profile of the line center and a quasi-statistical profile of a blue wing of the line. Such analysis predicts no heating of the gas in the ionization zone for positive corona and considerable heating for negative corona

Study of the rovibrational levels of ground state excited hydrogen molecules by laser photodetachment and emission spectroscopy

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