Effect of dielectronic recombination excitation in the solar chromosphere-corona transition region

The intensities of lines emitted from the solar chromosphere-corona transition region and observed on the earth are calculated by considering excitation of electrons to the upper level caused by electron-impact excitation and dielectronic recombination excitation processes. For the lines under investigation, the electron-impact deexcitation rates are negligibly small in comparison with spontaneous transition probabilities. Hence, electrons from the upper level deexcite through spontaneous transition only, emitting photons of wavelength corresponding to the energy difference between two levels. To determine the contribution of dielectronic recombination excitation (DRE) to the excitation mechanism, the calculations are repeated with exclusion of DRE. It is found that DRE contributes significantly and that its contribution may be much larger than that of electron-impact excitation.     

Effect of dielectronic recombination excitation in the solar x-ray lines of calcium-ions

The effect of dielectronic recombination as an excitation process in the intensity of solar x-ray lines of calcium ions is investigated. It is found that x-ray line intensities are enhanced by 15% to 88% with the inclusion of dielectronic recombination as an excitation mechanism.     

Density effects on the spectral intensities of dielectronic satellite line in dense plasmas

Summary In this paper we present a theoretical analysis of the spectral intensity of dielectronic satellite lines in dense plasmas. The ion microfield causes an oscillator strength mixing that alters the spectral intensity of such a transition. Numerical calculations of this high-density effect have been performed for the most intense 2l2l′→1s2l He-like transitions.

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Riassunto In questo articolo si presenta un'analisi teorica dell'intensità spettrale delle linee di satellite dielettroniche in plasmi densi. Il microcampo ionico causa un mescolamento delle forze dell'oscillatore che modifica l'intensità spettrale di una tale transizione. Si sono effettuati calcoli numerici di questo effetto ad alta densità per le transizioni più intense del tipo 2l2l′→1s2l.

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Резюме В этой работе мы предлагаем теоретический анализ спектральной интенсивности диэлектронных линий сателлитов в плотной плазме. Микрополе иона вызывает смешивание сил осцилляторов, что изменяет спектральную интенсивность такого перехода. Проведены численные вычисления эффекта высокой плотности для наиболее интенсивных Не-подобных переходов 2l2l′→1s2l.

     

Recent dielectronic recombination experiments

New recombination experiments with merged cold beams of electrons and atomic ions have been carried out at the storage ring facilities TSR in Heidelberg, ESR in Darmstadt, and CRYRING in Stockholm. A brief overview is given on the recent activities in which the Giessen group was engaged. Topics of this research were dielectronic recombination (DR) of astrophysically relevant ions, recombination of highly charged ions with respect to cooling losses in storage rings, field effects on DR, search for interference effects in photorecombination of ions, correlation effects in DR of low-Z ions, spectroscopy of high-Z ions by DR, and lifetimes of metastable states deduced from DR experiments. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of dielectronic recombination on the charge-state distribution and soft X-ray line intensity of laser-produced carbon plasma

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.     

Radiative recombination of excitons in semiconductors at high excitation intensities

The shape of the exciton luminescence band of the gaseous phase of free excitons in crystal Si is investigated under high level excitation. Only the exciton-exciton interaction is considered and the influence of collisions of excitons with phonons and electrons is not taken into account. The theoretical shape of the exciton luminescence band qualitatively agrees with experiment. The process of the radiative Auger-recombination of two indirect excitons without the participation of phonons is studied in Ge and Si. The expression for the frequency and temperature dependence of the probability of radiation is obtained. The band has the asymmetrical Gaussian form with the steep short-wave tail. The predicted luminescence band in Ge is shifted at the long-wavelength side from the well-known exciton luminescence bands with participation of the phonons. The selection rules for the probability amplitude of the process under consideration are obtained.     

高离化态Cu18+离子的双电子复合及共振转移激发过程的理论研究

在准相对论理论框架下计算了Cu18+离子的双电子复合截面,分析了组态相互作用对截面的影响.基于这些数据,在冲量近似下,通过对靶原子中电子动量分布的卷积,进一步得到了Cu18+与H2碰撞过程中的共振转移激发截面,并与已有的实验结果作了比较,符合得很好.     

Angular distribution of photons in dielectronic recombination

We have calculated the angular distribution of photons emitted after dielectronic recombination of highly charged uranium ions and obtained differential cross sections for resonant transfer and excitation in collisions of U⁹⁰⁺ with C atoms using the impulse approximation. This revised version was published online in July 2006 with corrections to the Cover Date.     

高离化金离子态-态双电子复合速率系数

研究了类铍Au⁷⁵⁺离子三类态-态双电子复合过程，基于多组态准相对论自洽场 方法和 扭曲波方法，计算了该离子在电子温度0.6—10.0keV范围内的态-态双电子复合速率系数， 并讨论了它们随电子温度、复合类型和上下能态的变化. 关键词： 75+离子')" href="#">Au⁷⁵⁺离子 态-态双电子复合     

类锂离子KLL双电子复合过程研究

采用相对论扭曲波方法,理论研究了高离化态类锂离子I~(50+)、Ho~(64+)、Bi~(80+)的KLL双电子复合过程,得到了双电子激发态的共振能量和双电子复合截面,利用自电离和辐射跃迁速率,得到了对应谱线的总宽度,并与已有的理论和实验结果进行了对比,理论较好地解释了最近的实验结果.     

类锂离子KLL双电子复合过程研究

采用相对论扭曲波方法,理论研究了高离化态类锂离子I50+、Ho64+、Bi80+的KLL双电子复合过程,得到了双电子激发态的共振能量和双电子复合截面,利用自电离和辐射跃迁速率,得到了对应谱线的总宽度,并与已有的理论和实验结果进行了对比,理论较好地解释了最近的实验结果。     

Tables for the computation of dielectronic recombination coefficients

Two sets of tables are presented which facilitate the rapid calculation of hydrogenic ion dielectronic recombination coefficients for ions of charge z?17 and for ions of charge z>17     

Co-like Au52+离子双电子复合的理论研究

基于准相对论Hatree-Fock理论,采用Cowan程序详细计算了Co-like A u52+离子的双电子复合速率系数、自电离几率以及自电离能级.计算结果表明:由于径向波函数的穿透效应使得该离子自电离能级3d84l5s(l=s、 p、d、f)升高,造成能级间隔不随外层激发电子轨道角动量的增加单调减小的异常现象,即Δ(E3d8 4l5d-E3d84l5p)＞Δ(E3d84l5p-E3d84l5s)＞Δ(E 3d84l5f-E3d84l5d);双激发自电离态平均自电离几率具有特定的变化关系;双电子复合速率系数随着电子温度逐渐增加具有共振、高温收敛等特点,且双激发态轨道角动量大且宇称为奇的通道复合速率系数较大,其中辐射衰变通道为3d84fnd-3d9nd 的复合过程占优势,在Te=0.49*"KeV时共振峰αDR=1.01×10-11(cm 3sec-1).     

类氦氪离子双电子复合的相对论计算

本文采用相对论性的Flexible Atomic Code (FAC)程序计算类氦氪离子的双电子复合截面及速率系数。其中自电离速率的计算采用相对论扭曲波近似，并考虑了组态相互作用的影响。文中还将所得的自电离和总辐射速率与采用MCDF和HULLAC计算得到的结果作了比较。我们检验了n-3标度律的有效性并用它对速率系数做了外推。文中还讨论了辐射分支比随不同共振峰和原子序数的变化以及级联辐射的影响。     

Total dielectronic recombination rate coefficient for Co-like tungsten

Ab initio calculation of the total dielectronic recombination (DR) rate coefficient from the ground state 3s²3p⁶3d⁹(J=5/2) of Co-like tungsten is performed employing the relativistic distorted-wave approximation with configuration-interaction. The DR contributions mainly come from complex series 3d⁸4ln′l′. The complex series 3p⁵3d¹⁰n′l′, 3p⁵3d⁹4ln′l′ and 3d⁸5ln′l′ also contribute significantly to the total DR rates at relatively high electron temperatures. The l′ and n′ dependences of the partial rate coefficient are investigated. The inclusion of decays into autoionizing levels followed by radiative cascades (DAC) enlarges the total DR rate coefficients by a factor of about 10%. The level-by-level extrapolation method is developed to include DAC effects. The total DR rate coefficients are fitted to an empirical formula. It is shown that at temperatures above 2.5 keV the Burgess-Merts (BM) semiempirical formula can provide DR results with an accuracy of about 15%, whereas at electron temperatures below 100 eV it underestimates the DR rate coefficients by up to a few orders of magnitude and its temperature dependence is completely inadequate. The comparison of the results for Ni-like and Co-like tungsten shows that these two sets of DR rate coefficients are very close in magnitude at relatively high electron temperatures.     

Many-body perturbation theory applied to dielectronic recombination resonances

A procedure to calculate dielectronic recombination cross-sections based on relativistic many-body perturbation in an all order formulation is presented. Complex rotation is employed in order to handle autoionizing states. The method is applied to recombination of lithium-like neon and lithium-like argon and the results are compared with experiments. This revised version was published online in July 2006 with corrections to the Cover Date.