Recombining Hydrogen Plasma Research Articles

Decomposition of carbon dioxide by recombining hydrogen plasma with ultralow electron temperature

We examined the rate coefficient for the decomposition of CO2 in low-pressure recombining hydrogen plasmas with electron temperatures between 0.15 and 0.45 eV, where the electron-impact dissociation was negligible. By using this ultralow-temperature plasma, we clearly observed decomposition processes via vibrational excited states. The rate coefficient of the overall reaction, CO2 + e → products, was 1.5 × 10−17 m3/s in the ultralow-temperature plasma, which was 10 times larger than the decomposition rate coefficient of 2 × 10−18 m3/s in an ionizing plasma with an electron temperature of 4 eV.

Movement of electron when recombining in hydrogen plasma

An analytical model and the results of modeling are presented for movement of electrons in recombining hydrogen plasma. It is shown that in case of taking into account the magnetic moment and angular momentum as well as spin flip of electron in magnetic field the electron comes to the orbit with angular momentum ħ/2. If azimuthal and radial components of kinetic energy of electron are equal then the full energy of such the orbits is 13.6 eV.

Optical Emission of Molecular Hydrogen in a Recombining Hydrogen Plasma

AbstractWe observed optical emission of molecular hydrogen in a recombining hydrogen plasma with an electron temperature of 0.1 eV and an electron density of 3 × 1012cm–3. The optical emission intensities of molecular hydrogen in the recombining plasma were roughly 10%–45% of those in an ionizing plasma with an electron temperature of 4 eV. The ratio was greater for a transition line originated from an excited state with a larger vibrational quantum number. Because of the low electron temperature of 0.1 eV, the production processes of excited states are not considered electron impact excitation in the recombining plasma. Possible recombination processes are discussed which produce excited states of molecular hydrogen in the recombining plasma (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Regimes with Recombining Plasma in the ITER Divertor

AbstractThe possibility to establish regimes with dense recombining hydrogen plasma in ITER divertor is considered. It is shown that due to the large difference between effective heat transmission coefficients of neutral gas and plasma there is a bifurcation of plasma parameters near the target. Due to this bifurcation a neutral gas layer can occur between the divertor plate and the plasma. The criterion of establishing of this gas layer is found.

Far-infrared transmission through the afterglow of a Z-pinch discharge in hydrogen

The absorption coefficient of a recombining hydrogen plasma has been measured for far-infrared radiation of wavelength 57 mu m. This coefficient is of the order of five times greater than that calculated from the electron density and temperature values, for most of the time interval for which they are available. No cause has been identified for this discrepancy.

Numerical Investigation of Laser Oscillation in a Recombining Hydrogen Plasma Interacting with Helium Gas in TPD-I

A numerical investigation on the basis of a collisional-radiative (CR) model has shown that laser oscillation between the levels with the principal quantum numbers i = 2 and 3 can be generated in a recombining hydrogen plasma interacting with a dense helium gas as a cooling medium in TPD-I, which is a magnetically confined quiescent high-density plasma source consisting basically of two parts, namely, the discharge region with the cathode at the center of the cusped magnetic field and the plasma column region with the axial magnetic field. The population inversion is found to exceed significantly a threshold level for the laser oscillation even in the quasi-steady state when the hydrogen plasma with ne = 1013 ~ 1014 cm−3 interacts with the helium gas with a pressure of about 50 Torr.

The Behaviour of Population in a Plasma Interacting with an Atomic Gas

The processes leading to the population inversion are investigated in a recombining hydrogen plasma which is interacting with a cool and dense neutral hydrogen gas by using the rate equations on the basis of a collisional-radiative (CR) model and the energy equations for electrons, ions and neutral particles. The quasi-steady state (QSS) approximation is used only for the levels i lying above a certain level i* which is not the first excited level. The calculations have shown that the quasi-steady state cannot be realized while intense energy-flows due to the collisional processes exist between different kinds of the particles such as the electrons and the ions in the plasma, and that the population inversion is realized only in the quasi-steady state following the transient phase. The effects of the initial conditions of the hydrogen plasma and of the introduced neutral hydrogen gas on the overpopulation density are also discussed.

Anomalous results obtained for long-path measurements of both continuum absorption and level populations in a pure recombining hydrogen plasma

The continuum absorption in a pure hydrogen plasma between 6400 and 6545 AA has been measured using laser spectroscopy over a 400 m path length. Contributions to the opacity from a number of processes have been calculated, including the bound-free absorption from high-lying neutral hydrogen levels, estimated from a direct interferometric measurement of the n=2 level population. Theoretical values for the n=2 level population, calculated using a 20-level collisional-radiative code, disagree with the measured values by up to a factor of three, and calculations of the absorption fail to explain the measured results by approximately an order of magnitude. No explanation for these discrepancies is obvious.

Direct Measurement of Population Inversion in a Recombining Hydrogen Plasma by the Laser-Induced Fluorescence Method

In a stationary recombining hydrogen plasma, resonance fluorescence of the ${\mathrm{H}}_{\ensuremath{\alpha}}$ line is measured by the laser-induced fluorescence method. Population inversion between $n=2$ and $n=3$ levels is verified by the observation of the fluorescence reduction. Marked inversion is obtained only in the upstream region of a flowing recombining plasma. Extinction of the inversion towards the downstream region is explained by the effect of the plasma opacity.

Population inversion between the ground and first excited states in a recombining hydrogen plasma

Plasma conditions for generating a population inversion between the ground and first excited states in a recombining hydrogen plasma have been investigated on the basis of the CR model. Population inversion can be expected when three-body recombination plays a dominant role; the required regions of electron density and temperature are specified. It is shown that upper bounds exist for the ground-state population density at given electron density and temperature. Larger inversion densities can be obtained between the ground and first excited states than between excited levels. Numerical results are presented.

Population inversion in recombining hydrogen plasma

The collisional-radiative model is applied to a recombining hydrogen plasma in order to investigate plasma conditions in which a population inversion between the energy levels of hydrogen can be generated. Population inversion is expected in plasmas for which three-body recombination makes a large contribution to the recombining processes and the effective recombination rate is larger than a critical value for a given electron density and temperature. Calculated results are presented in figures and tables.

Population Inversion between the Ground State and the First Excited State in Recombining Hydrogen Plasma

Population Inversion between the Ground State and the First Excited State in Recombining Hydrogen Plasma

Hydrogen emission-line spectra in quasars and active galactic nuclei

An attempt is made to account for the observational fact that the intensity ratios of the lower Balmer lines seen in emission from QSOs, type 1 Seyfert galaxies, and other related active galaxies are not what would be expected from the conventional picture of lines generated in a recombining hydrogen plasma. Previous observations of emission-line intensities in QSOs and Seyfert galaxies are reviewed. The various processes included in the rate coefficients of the calculations are then described, viz., free-free, bound-free, and bound-bound transitions, radiative transfer, and angular-momentum mixing. The strengths of the various emission lines are calculated by using more accurate values for the transition rates, including excitation and deexcitation simultaneously, and providing for finite rates in optically forbidden transitions. Numerical results are presented for the cases of ground-state collisional excitation, reabsorption of the upper Balmer lines, and collisional deexcitation. The results are applied to construct a model for the emission-line gas in a QSO and to discuss limits on models of Seyfert galaxies.