Determination of the electron concentration and temperature,as well as the reduced electric field strength,in the plasma of a high-voltage nanosecond discharge initiated in atmospheric-pressure nitrogen by a runaway electron beam

We report on the results of spectroscopic measurements of electron concentration N _e and temperature T _e , as well as the reduced electric field strength E/N in the plasma of a high-voltage nanosecond discharge in the gap with a strongly nonuniform electric field distribution, which is filled with nitrogen under the atmospheric pressure. The possibility of using the method for determining T _e and E/N, which is based on the determination of the ratio of the peak intensities of the ionic N ₂ ⁺ (λ = 391.4 nm) and molecular N₂ (λ = 394 nm) nitrogen bands, is proved. We detected the mean values of quantities N _e , T _e , and E/N amounting to ～2 × 10¹⁴ cm^?3, ～2 eV, and ～240 Td, respectively. In addition, the dynamics of these quantities is determined.     

Diagnosis of electron temperature in Ar/O2 mixed gas and destruction of toluene/benzene by positive dc discharge plasma

The electron temperature (T_e) of positive dc corona plasma in Ar/O₂ atmosphere was diagnosed, and plasma decomposition of toluene/benzene was studied in a razor–plate reactor. Experimental results revealed that T_e would increase with corona current until it reached a peak value, and then decrease; the volume fraction of Ar (φ_Ar) in Ar/O₂ mixed gas also influenced T_e, the higher φ_Ar, the lower T_e. Though the decomposed volume fraction of toluene/benzene was positively related to the input power, the decomposition efficiency did not monotonically increase with the specific energy density. The highest energy yield reached 3.8 g-toluene/kWh and 2.4 g-benzene/kWh, respectively.     

Stepwise ionization in a non-equilibrium,steady-state hydrogen plasma

The paper considers a non-equilibrium, steady-state hydrogen plasma with 10¹⁰ ? N_e, cm^-3 ? 10¹⁷ and 8000 ? T_e, °K ? 64,000. The following two cases are analyzed: (1) the plasma is optically thin for all atomic lines and (2) the plasma is optically thick towards the Lyman lines and optically thin for all other lines. Analytical expressions have been obtained for populations and ionization frequencies of excited levels. Populations of the excited levels obtained from the analytical formulas are in good agreement with numerical calculations.     

Electron density diagnostic potential of Ar XIV soft X-ray emission lines

Theoretical electron density-sensitive line ratios R₁-R₆ of Ar XIV soft X-ray emission lines are presented. We found that these line ratios are sensitive to the electron density n_e, and the ratio R₁ is insensitive to electron temperature T_e. Recent work has shown that accurate atomic data, such as electron impact excitation rates, is very important for an reliable determination of the electron density of laboratory and astrophysical plasmas. Present work indicates that the maximum discrepancy of line ratios introduced from different atomic data calculated with distorted wave and R-matrix approximations, is up to 18% in the range of . By comparison of these line ratios with experiment results carried out in electron beam ion trap (EBIT-II), electron density of the laboratory plasma is diagnosed, and a consistent result is obtained from R₁, R₂ and R₃. Our result is in agreement with that diagnosed by Chen et al. using triplet of N VI. A relative higher diagnosed electron density from R₂ is due to its weak sensitivity to electron temperature. A better consistency at lower T_e indicates that temperature of the laboratory plasma is lower than logT_e(K)=6.5. Comparison between the measured and theoretical ratios reveals that 32.014 Å  line is weakly blended by lines from other Ar ions, while 30.344 Å  line is strongly contaminated.     

The contribution of dissociative processes to the production of atomic lines in hydrogen plasmas

The contribution of molecular dissociative processes to the production of atomic lines is considered for a steady-state hydrogen plasma. If the contribution of dissociative processes is dominant, a substantial simplification in plasma diagnostics can be achieved. Numerical calculations have been performed for the production of Balmer α, β, and γ lines in hydrogen plasmas with medium and large degrees of ionization (x ? 10^-4) and for 5000 ? T_e, K ? 45,000 and 10¹⁰ ? N_e, cm^-3 ? 10¹⁶.     

Anomalous slowdown of relaxation in an ultracold plasma

Recent experiments by T.C. Killian et al. [Phys. Rev. Lett. 83, 4776 (1999)], in which an ultracold plasma (N _e～2×10⁹ cm^?3, T _e～0.1K, and T _i～10 μK) with anomalously long lifetime of ～100 μs was obtained, are explained based on a previously developed theory. The results of computer simulations of the plasma transition into a metastable state and initial heating of electrons up to several K are presented. An expression earlier obtained for the rate of the metastable plasma recombination agrees with the measured anomalously long lifetime. A conclusion is drawn that the previously predicted new physical object—a metastable overcooled plasma—is realized experimentally.     

X-ray spectroscopic diagnostics of ultrashort laser-cluster interaction at the stage of the nonadiabatic scattering of clusters

X-ray spectroscopic diagnostics of laser-cluster interaction at the stage of nonadiabatic scattering of clusters and formation of a spatially uniform plasma channel has been performed. The experimental investigations have been carried out on a Ti:Sa laser setup with a pulse duration of about 65 fs and an energy up to 600 mJ. It has been shown that, within 10 ps from the beginning of a laser femtosecond pulse, the laser-cluster interaction forms a uniform plasma channel with a length of 0.4 to 1 mm with the parameters N _e ～ 10¹⁹?10²⁰ cm^?3 and T _e ～ 100 eV.     

Investigation of the dependency of JET midplane separatrix density as a function of engineering parameters

Midplane separatrix density is a crucial parameter in tokamaks since it strongly impacts divertor conditions. Scaling midplane separatrix density, n_{e, SEP} , and pedestal density, n_{e, PED} , as function of engineering parameters such as auxiliary heating P_injected, toroidal magnetic field B_T, and plasma poloidal current I_p are relevant to observe the effect of tuning these parameters on, for example, quality of confinement and divertor regime governed by n_{e, PED} and n_{e, SEP} , respectively. Thus, a dataset of JET H-mode pulses performed with Iter like wall (ILW) has been analysed. Midplane density data are collected from an HRTS (high-resolution Thomson scattering) diagnostic and n_{e, SEP} is determined using the power balance method. Parallel heat flux model is chosen using transport code SOLEDGE2D (S2D) applying power balance method over a simulated n_{e, SEP} and T_{e, SEP} profiles to obtain separatrix positions. The parameters are averaged over time windows with order of (85–185 ms ) and the magnetic configuration has been fixed to avoid divertor geometrical effect on n_{e, SEP} determination, configuration chosen is corner–corner. A ratio between separatrix density and pedestal density at outer midplane ranges between 0.3 and 0.7 on the data set. A scaling law of n_{e, SEP}/n_{e, PED} is obtained as function of P_injected, B_T, and I_P.     

Hard X-ray emission by clusters in an intense femtosecond laser field during collective recombination

We consider the new mechanism of X-ray generation by clusters under irradiation by femtosecond laser pulses, the so-called collective photorecombination. We develop the theory of the photo-recombination of electrons that pass from atomic clusters at the outer ionization to the ground level of a homogeneously charged cluster. Such a cluster is considered to be a quantum potential well. The dipole approximation is inapplicable for this process. We conclude that X-ray photons in collective photorecombination on a charged cluster as a whole have an energy that is much larger than that for photorecombination on separate atomic ions inside the cluster. For a typical cluster of 2.25 × 10⁶ electrons, with a radius R = 300 Å, and a number density of plasma electrons n _e = 2 × 10²² cm^?3, we find that at a 5% outer ionization of this cluster, the energy of hard X-ray photons is 7.2 keV.     

The argon resonance continuum in the far-VUV between 50 and 79 nm

The photoionization cross section σ₁(λ) of the Ar(I) ground state was determined by absolute measurements of the Ar(I) resonance continuum between 50 and 79 nm. The vacuum ultraviolet (VUV) radiation originates from the axis of an Ar-He mixture plasma generated in a cascaded arc chamber of 2 mm φ at atmospheric pressure with arc currents of 80 and 96 A. From spectroscopic partial local thermodynamic equilibrium plasma diagnostics, the plasma properties n_e, n⁺_Ar and T_e are obtained, which are necessary for a determination of σ₁(λ). Good agreement is found between the resulting cross section of this work and data from absorption experiments. Only three theories are confirmed by our experiments. A pure Ar cascade arc is proposed as calculable stationary source of VUV continuum radiation between 55 and 79 nm.     

电子回旋共振等离子体特性及其对生长氮化镓晶膜的影响

为了解并优化在电子回旋共振等离子体辅助化学汽相沉积GaN晶膜的工艺研究中的等离子体特性,利用朗缪尔探针及法拉第筒系统地测量了离子密度(N_i)、等离子体势(V_p)、电子温度(T_e)及离子流强(J_i)等多个等离子体参量随微波功率(P_w)及沉膜室气压(p)变化的关系.给出了在P_w＝850W,p＝0.22Pa时,上述等离子体参量的轴向及径向分布.GaN晶膜的生长速率、电学及晶体学性能 关键词：     

Etude spectroscopique de l'effet d'anode

Spectral lines of LiI emitted by an anodic plasma, produced during electrolysis of a KCl-LiCl mixture, have been observed. This paper deals with diagnostic studies of this plasma and is based on a comparison of observed line profiles for LiI(2P-3D), (2P-4S) and (2P-4D, 4F) with calculated values derived from the Griem-Baranger impact theory. We have found, from the ensemble of the results, that the electron density in the plasma center is N_e(0) ? 1·8×10¹⁷ cm^-3, the electron temperature is T_e(0) ? 9×10³ °K, and the plasma thickness is l ? 200 μ.     

Lower and upper variational bounds in calculations of Coulomb and nuclear systems

All formulas that are necessary for deriving not only upper (E _U) but also lower (E _L) variational bounds on the energy of systems featuring a few nonrelativistic particles are obtained with trial functions in the form of expansions in multidimensional Gaussian functions or exponentials. For potentials that are used most widely, all matrix elements are expressed in terms of known functions, a circumstance that simplifies considerably relevant numerical calculations. This is so for systems featuring an arbitrary number of particles in the case of a Gaussian basis and for three-particle systems in the case of an exponential basis. Numerical results for E _U and E _L, which are characterized by record accuracies, are presented for some Coulomb and nuclear systems such as the He atom; the e ⁺ e ^? e ^?, ppμ^?, 3α, and 4α systems; and hypertritium (pnΛ). Lower bounds with exponential trial functions are obtained for the first time (the corresponding formulas are presented for the first time as well); for a Gaussian basis, lower bounds for Coulomb systems have not been known either. Given E _L and E _U, limits within which the exact value of energy, E ₀, lies can be indicated with confidence. Moreover, an analysis of the correlation between E _L and E _U with increasing number of terms in the expansion of the trial function makes it possible to improve the accuracy (at least by one order of magnitude) of the value E _∞ extrapolated to infinity. By considering specific examples, it is shown that the exponential basis is advantageous in relation to the Gaussian one.     

Spin-orbit effects in the ground X2Π state and two low-lying excited valence states B2Π and L′2Φ for NO

The potential energy curves and spectroscopic constants B _e , ω _e , ω _e χ _e , α _e , D _e of the six Ω states (X ²Π_1/2, ? 3/2, B ²Π_1/2, ? 3/2 and L ^′2Φ_{5/2,   7/2}) of the NO radical molecule were calculated using spin-orbit multi-configuration quasi-degenerate perturbation theory (SO-MCQDPT). The spin-orbit coupling effect was considered via the state interaction approach with the full Breit-Pauli Hamiltonian. The spin-orbit splitting energy between the X ²Π_1/2 and X ²Π_3/2 states of the NO radical is 129.61 cm^-1, which agrees reasonably well with the experimental value of 123.13 cm^-1. For the B ²Π_{1/2,   3/2} states, the spin-orbit coupling (SOC) splitting energy is 35.99 cm^-1, the corresponding experimental value is 31.7 cm^-1. The SOC splitting value of the L ^′2Φ_{5/2,   7/2} states was calculated to be 103.2 cm^-1. The spectroscopic constants R _e , ω _e , ω _e χ _e , B _e , α _e , D _e are in reasonable agreement with available experimental and theoretical data for the six Ω states.     

Velocity distribution of plasma electrons in the negative H2- and He-glow with superimposed longitudinal magnetic field

The negative glow plasma has been found nearly field free in axial direction. Therefore plasma electrons in the stationary glow can thermalize down to the temperature of the neutral gas, whenever their diffusion—and recombination—lifetime is high enough. Applying Boltzmann's equation to this problem, the conditions of thermalization of plasma electrons are derived as a function of the outer parameters of the plasma: vessel diameter 2R, neutral gas pressurep and longitudinal magnetic fieldB. — If plasma electrons have a too short diffusion—and recombination—lifetime to be in thermal equilibrium with the neutral gas, the electron energy increases. For this case the distribution function of plasma electrons is derived using Boltzmann's equation. Approximating the calculated energy distribution by a Maxwellian distribution function, the electron temperature in the glow is obtained as a function of the parameters:R, p, B. OurT _e -measurements carried out in the H₂- and He-glows of different tube diameters, neutral gas pressures and magnetic fields agree closely with the theoretical results. TheT _e -measurements have been performed with Langmuir probes and by the method of reversal of the radial ambipolar electric field in a longitudinal magnetic field.     

Observation and analysis of the Xe−I collisional-pair photoassociation spectrum

The interpretation of the photoassociation spectrum arising in collisions of Xe and I atoms is refined with allowance for new data concerning the interaction potential of Xe and I collisional pairs. Spectroscopic constants for the XeI(B) state are determined:R′ _e =3.264961 Å,D′ _e =33,289.05 cm^?1,w′ _e =113.867826 cm^?1, andw′ _e x′ _e =0.238304 cm^?1.     

Effects on spectroscopic properties for several low-lying electronic states of CS molecule by core-valence correlation and relativistic corrections

The potential energy curves (PECs) of six low-lying electronic states (X¹Σ⁺, a³Π, a′³Σ⁺, d³Δ, e³Σ⁻ and A¹Π) of CS molecule have been investigated using the full valence complete active space self-consistent field (CASSCF) method followed by the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach with large correlation-consistent basis sets. Effects on the PECs by the core-valence correlation and relativistic corrections have been taken into account. And the two corrections are performed at the level of cc-pV5Z basis set. The way to consider the relativistic corrections is to use the second-order Douglas-Kroll Hamiltonian approximation. Using the CCSD(T), MRCI and MRCI with the Davidson modification (MRCI + Q), the PECs of electronic states involved are extrapolated to the complete basis set (CBS) limit. With the PECs, the spectroscopic parameters (T_e, R_e, ω_e, ω_ex_e, ω_ey_e, α_e, β_e, γ_e and B_e) of the six low-lying electronic states are determined. These parameters are in excellent agreement with the experimental data. The complete vibrational states are computed for the six low-lying electronic states when the rotational quantum number J equals zero, and the inertial rotation constants of the first 23 vibrational states are reported, which agree favorably with the RKR data. Comparison with the measurements shows that the two-point total-energy extrapolation scheme can obviously improve the quality of spectroscopic parameters and molecular constants.     

Modulated electron spectrum of the light scattered by a magnetized arc plasma

Measuring the spectrum of laser light scattered by a magnetized arc plasma (n _e =1.2 × 10¹⁶ cm^?3,T _e =3.2 eV, α=0.6,B _z =120 kG) we observe deviations from the normal thermal spectrum. The observed modulation is most probably due to the influence of the magnetic field. Two other less likely possibilities (enhanced electron oscillations or the existence of an additional colder electron component) are discussed.     

Laser magnetic resonance for the v = 1 ← 0 transition of SeO (X3Σ−) by a CO2 laser

The vibration-rotation transitions for a fundamental band of SeO (X³Σ^?) were studied by means of the infrared laser magnetic resonance (LMR) method employing a CO₂ laser. The LMR spectra arising from five SeO isotopic species except ⁷⁴SeO were detected and analyzed. Band origins for these species were determined. Molecular parameters ω_e, ω_eχ_e, B_e, and α_e, were obtained with the aid of the reduced mass relations. For ⁷⁷SeO the axial component of magnetic hyperfine interaction was obtained.     

Sur l'evolution des proprietes physiques de la perovskite GdCoO3 entre 77 et 1200 K

GdCoO₃, which has the GdFeO₃ structure, has been studied between 77 and 1200 K by D.T.A., X-ray diffraction, magnetic susceptibility, electric conductivity and thermoelectric power. All properties observed, although different from those of LaCoO₃, fit with the corresponding Goodenough localized electron model. With rising temperature cobalt ions pass progressively from a low-spin Co^III(t⁶_2ge_g⁰) state to a Co³⁺(t⁴_2ge_g²) high-spin state.