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1.
The power radiated by an optically thin, low-density (Ne ≤ 1014 electrons/cm3) plasma has been calculated for the electron temperature range 1–106 eV taking into account resonance line emission, direct recombination radiation, dielectronic recombination radiation, and bremsstrahlung from the ions of a given element. The ionization structure has been determined by using a corona equilibrium model in which collisional ionization and inner-shelled excitation followed by autoionization are balanced by direct radiative and dielectronic recombination. Based on the results for respresentative elements from carbon through nickel, graphs are presented of the maximum radiated power, the maximum emission temperature, and the mean charge at the maximum for each shell as functions of the atomic number Z. Assuming that the maximum emission temperature can be achieved, aluminum and iron are predicted to be the most efficient K-shell radiators for Z ≤28. 相似文献
2.
C.Bruce Tarter 《Journal of Quantitative Spectroscopy & Radiative Transfer》1977,17(4):531-536
Radiative energy losses from twelve low and moderate Z elements are calculated for temperatures ranging from 2 eV to 20 keV. Each element is assumed to be in coronal equilibrium, so that the ionization structure is determined by balancing collisional ionization and autoionization against radiative and dielectronic recombination. The radiative losses are calculated by adding the emission due to bremsstrahlung, radiative and dielectronic recombination, 2-photon processes, and line radiation. Polynomial fits to the loss rates, suitable for use in computer programs, are given for each element. 相似文献
3.
X-ray emission spectra for L-shell of Li-like aluminium ions are simulated by using the flexible atomic code based on the collisional radiative model. Atomic processes including radiative recombination, dielectronic recombination, collisional ionization and resonance excitation from the neighbouring ion (Al^9+ and Al^11+ ) charge states of the target ion (Al^10+) are considered in the model. In addition, the contributions of different atomic processes to the x-ray spectrum are analysed. The results show that dielectronic recombination, radiative recombination, collisional ionization and resonance excitation, other than direct collisional excitation, are very important processes. 相似文献
4.
J. Davis V.L. Jacobs P.C. Kepple M. Blaha 《Journal of Quantitative Spectroscopy & Radiative Transfer》1977,17(2):139-147
Calculations are presented for the rates of radiative energy loss from tokamak plasmas arising from radiation processes involving collisions between electrons and multiply-charged Fe impurity ions. The distribution of ionization states is determined from the steady-state corona model. The inclusion of dielectronic recombination raises the temperature at which each ion has its maximum equilibrium abundance. For certain nonhydrogenic ions, the dielectronic recombination rates obtained from previous calculations are found to be overestimated due to the neglect of autoionization into an excited state of the recombining ion. Electron impact excitation of resonance line radiation in the far ultraviolet and X-ray regions is the dominant radiative cooling mechanism at temperatures where ions with bound electrons are abundant. However, the radiation emitted during dielectronic recombination can be more important than direct recombination radiation and bremsstrahlung. 相似文献
5.
Based on the multi-configuration Dirac-Fock method, theoretical calculations are carried out for the dielectronic recombination (DR) rate coefficients and the collision excitation rate coefficients of Sn^10+ ions. It is found that the total DR rate coefficient has its maximum value between 10eV and 100eV and is greater than either the radiative recombination or three-body recombination rate coefficients (the number of free electrons per unit is 10^21 cm^3) for the ease of Te 〉 1 eV. Therefore, DR can strongly influence the ionization balance of laser produced multi-charged tin ions. The related dieleetronie satellite cannot be ignored at low temperature Te 〈 5 eV. 相似文献
6.
U. Kentsch T. Werner G. Zschornack F. Grossmann V.P. Ovsyannikov F. Ullmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(3):297-305
Irq+ ( 41≤q≤64) ions with open-shell configurations have been produced in the electron beam of the room-temperature Dresden Electron
Beam Ion Trap (Dresden EBIT) at electron excitation energies from 2 keV to 13 keV. X-ray emission from direct excitation processes
and radiative capture in krypton-like to aluminium-like iridium ions is measured with an energy dispersive Si(Li) detector.
The detected X-ray lines are analyzed and compared with results from multiconfigurational Dirac-Fock (MCDF) atomic structure
calculations. This allows to determine dominant produced ion charge states at different electron energies. The analysis shows
that at the realized working gas pressure of 5×10-9mbar for higher charged ions the maximum ion charge state is not preferently determined by the chosen electron beam energy
needed for ionization of certain atomic substates, but by the balance between ionization and charge state reducing processes
as charge exchange and radiative recombination. This behaviour is also discussed on the basis of model calculations for the
resulting ion charge state distribution.
Received 12 July 2001 and Received in final form 10 September 2001 相似文献
7.
Banglin Deng Gang Jiang 《Journal of Quantitative Spectroscopy & Radiative Transfer》2012,113(12):1628-1634
The X-ray emission spectra of nickel plasma were simulated under the collisional radiative model (CRM) by using the flexible atomic code (FAC). The dynamical processes including collisional excitation (CE), radiative recombination (RR), dielectronic recombination (DR), collisional ionization (CI) and resonance excitation were considered in the model, and the rate coefficients of DR, RR as well as CI were consistent with previous results within 15%. It was found that the contributions to spectra from cascades and indirect processes could not be ignored. The intensities of spectral lines for lithium-like nickel L-shell ions are sensitive to the electron temperature. The good agreement between present spectral peaks and earlier observed results can be taken as a measure of the accuracy of the present work. 相似文献
8.
The KLL dielectronic recombination processes of highly charged He-like to C-like Kr ions have been studied experimentally. The measurement was performed on the newly developed Shanghai electron beam ion trap (Shanghai-EBIT) facility. Characteristic x-rays from both dielectronic recombination and radiative recombination are detected as the electron beam energy is scanned through the resonances. The KLL resonant strengths obtained are 5.41×10^-19, 4.33×10^-19, 3.59×10^-19, 2.05×10^-19 and 0.98×10^-19 cm^2 eV for He-like to C-like Kr ions, respectively. 相似文献
9.
M. B. Smirnov 《Laser Physics》2010,20(5):1009-1018
X-ray radiation is studied for large clusters consisting of 107–1010 atoms and irradiated by an intense laser pulse with an intensity ranged from (1014 up to 1018 W/cm2). The model is developed for such a laser plasma that includes the radiative transitions and the processes of excitation and quenching of multicharged ions of this plasma by electron impact. Due to interaction of a radiating multicharged ion with a surrounding plasma, spectral lines of emission are broaden and neighboring spectral lines are overlapped. As a result, the spectrum of radiation of multicharged ions is transformed into a continuous spectral band. The model under consideration includes important plasma processes including dielectronic recombination, spontaneous radiation, excitation, quenching and ionization of multicharged ions by electron impact. On the basis of the model developed the X-ray spectrum and spectral power are evaluated. In the range of laser intensities under consideration a laser plasma formed contains multicharged ions with charges Z = 26?36 that corresponds to the 3d-electron shell in the xenon case. 相似文献
10.
The yield and energy distributions of Cs atoms emerging from cesium layers, which are adsorbed on tungsten coated with a thin germanium film (1-to 2-monolayers thick), have been measured as a function of the incident electron energy, the amount of adsorbed cesium, and the substrate temperature. The measurements were performed by the time-of-flight technique with a surface ionization detector. At low cesium coverages (Θ < 0.1), the Cs atom appearance threshold at a substrate temperature T = 160 K is ~24 eV, which correlates with the Cs 5s-level ionization energy. As the electron energy is increased, the yield passes through a broad plateau and reaches saturation. The signal intensity in the plateau region decreases gradually with increasing cesium coverage and tends to zero for Θ > 0.14. For Θ ≥ 0.15, the cesium atom appearance threshold shifts to ~30 eV, which corresponds to the Ge 3d-level ionization energy and the plateau is replaced by a resonance peak at ~38 eV, which can be identified with the ionization energy of the W 5p 3/2 level. This peak is observed only for Θ < 0.3 and T = 160 K. For Θ ≥ 0.3, there appears a resonance peak at ~50 eV, and for Θ ≥ 0.5, another resonance peak appears at ~80 eV. These peak positions correlate with the ionization energies of the W 5p 1/2 and W 5s levels, and their intensity is maximum at Θ = 1. The Cs atom energy distributions for Θ < 0.15 consist of a bell-shaped peak with a maximum at ~0.55 eV, and those for Θ ≥ 0.15 contain two nearly resolved maxima, a broad one peaking at ~0.5 eV and a narrow one at ~0.35 eV. The above results argue for the existence of three channels of Cs atom desorption. One channel involves reverse motion of the Cs2+ ion; another channel, neutralization of the adsorbed Cs+ ion following the Auger decay of a vacancy in the Ge atom; and the third channel involves desorption of a CsGe molecule as it is repelled from a W core exciton. 相似文献
11.
The effect of dielectronic recombination in determining charge-state distribution and radiative emission from a laser-produced
carbon plasma has been investigated in the collisional radiative ionization equilibrium. It is observed that the relative
abundances of different ions in the plasma, and soft X-ray emission intensity get significantly altered when dielectronic
recombination is included. Theoretical estimates of the relative population of CVI to CV ions and ratio of line intensity
emitted from them for two representative formulations of dielectronic recombination are presented. 相似文献
12.
The most up-to-date photorecombination spectrum of Ga13+ and Ge14+ has been re-assessed with direct large-scale relativistic atomic structure calculations. The new temperature-dependent dielectronic recombination rate coefficients are presented in a form convenient for astrophysical plasma modeling, summarizing the importance of different multi-electron intra-shell core excitations in the target ions. Obtained results are expected to facilitate a more accurate determination of the ionization-recombination balance of multiply-charged gallium and germanium ions and to improve the diagnosis of the radiative energy loss rates from low-density high-temperature plasmas. 相似文献
13.
光致电离等离子体在宇宙中广泛存在于强辐射场附近. 近年来随着高能量密度实验装置的发展, 在实验室内也能构造出光致电离等离子体. RCF是一个基于The Flexible Atomic Code 数据的针对光致电离等离子体的辐射碰撞模型, 该模型模拟了两个光致电离实验, 其 理论结果中电离态分布和光谱与测量值符合得很好. 在理论模拟中发现, 光致电离等离子体中光致激发和碰撞激发过程对离子态布居和发射光谱都有非常重要的影响. 光致激发过程可以通过将离子激发到双激发态从而间接电离离子; 碰撞激发过程会因为电子将基态离子激发到电离截面小的单激发态而抑制光子对等离子体的电离. 光致激发过程可以加强类锂离子的类氦离子的卫线, 而碰撞激发过程会影响类氦离子谱线的线强之比. 相似文献
14.
Energy losses of 200 eV to 2 keV electrons reflected from a disordered EuO(100) crystal show a bulk plasmon loss consistent with just less than six “quasi free” electrons per EuO unit, and 5p → nd resonance losses above the 5p threshold. The ratio of intensity of the 4d10 4fn0 → 4d9 4fn+1 “giant resonance” loss at 142 eV to the corresponding direct recombination feature varies with energy, while the direct recombination and related Auger channels show similar energy dependence. 相似文献
15.
An injection type electro-luminescence in ZnSe crystal has been studied by using ZnSe-SnO2 hetero-junction at 20°K. In the emission peak observed around 2·70 eV, a clear energy shift toward the higher energy side with increasing injection current density has been found at low temperatures, which could be associated with the D-A pair (donor-acceptor pair) recombination process. The energy sum of the donor and acceptor activation is estimated to be larger than 137 meV. In the higher temperature region, this emission line turns out due to the ‘free-to-bound’ recombination, and the related acceptor ionization energy is considered to be ~120 meV. By taking into consideration the energies of bound exciton emission, the exciton localization energies and the related donor and acceptor ionization energies are evaluated. 相似文献
16.
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18.
A first temperature measurement of the expanded electron beam from a super-conducting magnet in the cooler of CRYRING is reported.
It is based on detection of a dielectronic recombination resonance in C2+. For this measurement C3+ was stored in the ring at 3 rm{MeV/amu} energy. A fit to the resonance with free transverse and longitudinal temperatures
gave 3.9 × 10-3 eV and 4.5 × 10-5 eV, respectively. The result is also compatible with the values of 10-3 eV for the transverse and 6.7 ×10-5 eV for the longitudinal component, in good agreement with expected values.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
J.N. Gau Yukap Hahn J.A. Retter 《Journal of Quantitative Spectroscopy & Radiative Transfer》1980,23(2):147-156
Dielectronic recombination rate coefficients for Mo32+ recombining to Mo32+ are given for electron temperatures of 1.4, 2.8, and 5.6 keV. Nonrelativistic results in the resonance approximation were obtained and tables of selected Auger (Aa) and radiative (Ar) rates, fluorescence yields, and dielectronic recombination rates are given. Excitation of 2p electrons to higher shells is found to be dominant over other transitions including direct capture at the temperatures considered. The effect of the cascade transitions is estimated to be of the order of 30%. Different angular momentum averaging procedures change the results very significantly. 相似文献
20.
R. Schuch W. Zong D. R. DeWitt H. Gao S. Asp J. Hvarfner E. Lindroth H. Danared A. Källberg 《Hyperfine Interactions》1996,99(1):317-323
We have measured dielectronic recombination rates and energies for n=0 transitions of Ne7+ and Ar15+ beams stored in CRYRING. The energy resolution was in the order of 10–2 eV FWHM; the absolute accuracy in the position of the resonances is in the same order. The energy positions of the dielectronic recombination resonances are compared to theoretical calculations of the fine-structure splittings. 相似文献