The KLL dielectronic recombination processes for highly charged krypton, iodine and barium ions

The KLL dielectronic recombination (DR) processes of ions from highly charged helium-like to oxygen-like krypton, iodine and barium ions are studied systematically in the relativistic distorted-wave approximation with configuration interaction. The KLL DR resonant energies, the corresponding resonant strengths and the theoretical spectra for each highly charged ion species are obtained. The results accord well with other available values. The behaviour of KLL resonant strengths for He-like ions with atomic number Z is analysed.     

State-selective quantum interference observed in the recombination of highly charged Hg 75+...78+ mercury ions in an electron beam ion trap

We present experimental data on the state-selective quantum interference between different pathways of photorecombination, namely, radiative and dielectronic recombination, in the KLL resonances of highly charged mercury ions. The interference, observed for well resolved electronic states in the Heidelberg electron beam ion trap, manifests itself in the asymmetry of line shapes, characterized by "Fano factors," which have been determined with unprecedented precision, as well as their excitation energies, for several strong dielectronic resonances.     

Characterization of compact bright soft X-ray source based on picosecond laser plasma

Radiation emission of silicon and aluminum plasmas produced by 40-ps laser pulses with peak intensity above 10¹⁴ W/cm² was studied. High-resolution soft X-rayspectra of H-like and He-like ions were analyzed to determine plasma parameters. We compared the line shape of resonance transitions and their intensity ratios to corresponding dielectronic satellites and the intensities of the intercombination lines of He-like ions with the results of model calculations. Such comparisons gave average values of the electron number density N_e=(1-1.9)×10²¹ cm^-3 and the electron temperature T_e=460–560 eV for Si plasmas and about 560 eV for Al plasmas produced by the first and the second laser harmonics. The plasma size is about 100 μm. According to our estimations, more than 10¹² photons were produced within the resonance line spectral width and in the solid angle 2π during the total decay period. PACS 41.50.+h; 52.25.Os; 52.50.Jm     

Dielectronic Recombination of Sn^10＋ Ions and Related Satellite Spectra

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.     

Generation and characterization of a bright X-ray source using picosecond laser

High-resolution soft X-ray spectra of H-like and He-like ions were produced from laser irradiated silicon and aluminum targets. Plasma size was about 100 μm. X-ray spectra were analyzed to determine plasma parameters. We compared the line shape of resonance transitions and their intensity ratios to corresponding dielectronic satellites and the intensities of the inter combination lines of He-like ions, with the results of model calculations. Such comparison gave average values of the electron density N _e=(1?1.9)×10²¹ cm^?3 and the electron temperature T _e=460–560 eV for Si plasmas and about 560 eV for Al plasmas produced by the first and the second laser harmonics. According to our estimations, more than 10¹² photons were produced within the resonance line spectral width and in the solid angle 2π steredian during the total decay period.     

类氢类氦类锂镁离子双电子复合的旁观电子角动量研究

类氢类氦类锂镁离子经中间双激发态进行的双电子复合过程在研究惯性约束聚变电子温度中占有很重要的地位.用准相对论方法计算了双电子复合经不同Rydberg态跃迁通道的复合速率系数,并给出不同离化度离子的双电子复合速率系数随电子温度的变化规律.显示出离子的相关能对峰值的电子温度有很大影响,当类氢离子跃迁通道的旁观电子角动量为1时双电子复合系数最大,而类锂离子是旁观电子角动量为3时最大. 关键词： 双电子复合 镁离子 角动量     

A first study of dielectronic recombination with the super-expanded electron beam in CRYRING

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.     

Isotope shifts of dielectronic resonances for heavy few-electron ions

Effects of the nuclear charge distribution upon the total cross-section of dielectronic recombination are investigated. We calculated isotope shifts of resonance energies for H-, He- and Li-like heavy ions in the relativistic domain from Z = 54 to Z = 94. We point out that the position of the resonances is most influenced in KLL transitions in very heavy elements and their shifts are most likely to be measurable for systems with intra-shell transitions. For these systems, dielectronic recombination experiments provide a new method to determine the parameters of the nuclear charge distribution.Received: 26 July 2004, Published online: 5 October 2004PACS: 34.80.Lx Electron-ion recombination and electron attachment - 31.30.Jv Relativistic and quantum electrodynamic effects in atoms and moleculesR. chiopu: Now at Institut für Physik, Johannes-Gutenberg-Universität, Mainz, Germany.     

KLn Dielectronic Recombination Process of B- Through He-like Cu Ions

The KLn dielectronic recombination processes of trapped highly charged B-like through He-like Cu ions are studied theoretically, and the theoretical results are used to analyse our previous experimental data at Heidelberg electron beam ion trap （EBIT）. The theoretical resonant positions agree with the experimental resonant positions to a precision of 0.4%, in comparison with the resonant positions of those highest peaks between theory and experiment. The experimental spectra are then fitted using a formula with the theoretical resonant energies and strengths, the result shows good overall agreement between theory and experiment over a wide electron energy range. The distribution of highly charged states is obtained from the fitting parameters.     

Ionization equilibrium and radiative energy loss rates for C,N, and O ions in low-density plasmas

The results of calculations of the ionization equilibrium and radiative energy loss rates for C, N and O ions in low-density plasmas are presented for electron temperatures in the range 10⁴–10⁷ °K (～1–10³ eV). The ionization structure is determined using the steady-state corona model, in which electron impact ionization from the ground states is balanced by direct radiative and dielectronic recombination. Using an improved theory, detailed calculations are carried out for the dielectronic recombination rates in which account is taken of all radiative and autoionization processes involving a single-electron electricdipole transition of the recombining ion. The radiative energy loss processes considered are electron-impact excitation of resonance line emission, direct radiative recombination, dielectronic recombination, and electron-ion bremsstrahlung. For all three elements, resonance line emission resulting from 2s?2p transitions produces a broad maximum in the energy loss rate near 10⁵°K(～ 10 eV).     

Recombination measurements at low energies with Au49+,50+,51+ at the TSR

Recombination of Au⁴⁹⁺, Au⁵⁰⁺, and Au⁵¹⁺ ions has been studied at the TSR. With Au⁵⁰⁺ ions a storage lifetime of only 2 to 4 s was observed with the magnetically expanded electron beam of the cooler at a density of n_e = 10⁷ cm^-3. This short storage time is a consequence of the highest recombination rate coefficient ever observed with an atomic ion (1.8·10^-6 cm³ s^-1 at zero relative energy E_rel = 0 between electrons and ions). At about 30 meV a huge dielectronic recombination resonance is found with a record small width of only about 15 meV. Such resonances fortuitously occurring near E_rel=0 are probably the main reason for the enhanced recombination rates observed with Au⁵⁰⁺, with Pb⁵³⁺ (in a recent experiment at LEAR) as well as with other complex ions. For Au⁴⁹⁺ and Au⁵¹⁺ the recombination rates are smaller by an order of magnitude. This revised version was published online in August 2006 with corrections to the Cover Date.     

“水窗”波段类氦Al离子2p-3dX射线激光的粒子数反转研究

报道类氦Al用离子2p—3d粒子数反转的理论与实验研究结果,实验中观测到ls2p—ls3p能级间的粒子数反转,详细研究了其反转系数与激光等离子体参数及靶结构的相互关系,并与理论计算结果进行了比较,得到了令人满意的结果。     

镁铝类氢类氦类锂离子双电子复合速率研究

 镁铝类氢类氦类锂离子经中间双激发态进行的双电子复合过程在用双示踪元素谱线强度比研究ICF电子温度中占有很重要的地位。计算了双电子复合经不同Rydberg态跃迁通道的复合速率系数，并给出不同离化度的总的双电子复合速率系数的变化规律，比较了它们在不同电子温度和不同跃迁通道的异同，对研究X射线激光、等离子体温度诊断等诸多应用领域提供了有价值的原子数据。     

KLL dielectronic recombination process of He-like to O-like xenon ions

In this work, the KLL dielectronic recombination (DR) processes of highly charged He-like to O-like xenon ions are studied systematically by using a DR program, which is based on the multi-configuration Dirac-Fock (MCDF) method. The KLL DR resonant energies and the corresponding resonant strengths are calculated, asizing especially the effect of the Breit interaction on the DR strengths. The theoretical KLL DR spectra are obtained and compared with the latest experimental results obtained in the Shanghai Electron Beam Ion Trap.     

Field enhanced dielectronic recombination of Si11+ ions

The enhancement of dielectronic recombination by applied electric fields has been observed and measured for the first time in a wide range of controlled and measurable fields using multiply charged ions. The heavy ion storage ring, CRYRING, at Stockholm University was used to store a beam of Si¹¹⁺ and collide it with a cold electron target. The observation of a substantial monotonic increase of the rate coefficient for the group of higher Rydberg states is in puzzling disagreement with theoretical calculations of electric field enhanced dielectronic recombination. This revised version was published online in July 2006 with corrections to the Cover Date.     

Recombination measurements at low energies with Ar16+ and Ar18+ ions in a dense, cold electron target

Recombination of multiply charged ions with electrons at very low relative energies has become a major topic of interest, due to the observation of rates which are enhanced beyond the expectations for radiative recombination. We present results for Ar¹⁶⁺ and Ar¹⁸⁺ ions from systematic measurements along the argon isonuclear sequence using a high density cold electron beam target (n_e = 7 × 10⁹ cm^-3) at the UNILAC of GSI. The transverse and longitudinal temperatures of the electron beam were determined from DR resonance features observed with metastable Ar¹⁶⁺ (2³S) ions. The rate at E_rel = 0 for radiative recombination of completely stripped Ar¹⁸⁺ calculated with electron beam temperatures kT_∥ = 0.002 eV, kT_⊥ = 0.2 eV amounts to α = 10^-9 cm³ s^-1. This is exceeded by nearly a factor of 10 by the rate measured in experiments with Ar¹⁸⁺ ions. This revised version was published online in August 2006 with corrections to the Cover Date.     

高离化态Hg和U离子的双电子复合过程的理论研究

在相对论多组态Dirac-Fock理论基础上，利用近期发展的计算双电子复合截面的程序，系统研究了高离化态类氦到类硼Hg和U离子的KLL双电子复合过程. 讨论了Breit效应和量子电动力学(QED)效应对Hg离子共振双激发态能级的贡献，得到了双激发态的共振能、总线宽和相应的双电子复合共振强度，所得结果与其他理论和实验结果都符合得很好. 在此基础上进一步研究了高离化态U离子的KLL双电子复合过程，并与已有的实验和理论结果作了比较.     

高离化态Hg和U离子的双电子复合过程的理论研究

在相对论多组态Dirac-Fock理论基础上,利用近期发展的计算双电子复合截面的程序,系统研究了高离化态类氦到类硼Hg和U离子的KLL双电子复合过程. 讨论了Breit效应和量子电动力学(QED)效应对Hg离子共振双激发态能级的贡献,得到了双激发态的共振能、总线宽和相应的双电子复合共振强度,所得结果与其他理论和实验结果都符合得很好. 在此基础上进一步研究了高离化态U离子的KLL双电子复合过程,并与已有的实验和理论结果作了比较. 关键词： 双电子复合 MCDF     

Ti、Cr类氦双电子复合速率系数的量子力学计算

本文用全量子力学方法计算了Ti、Cr类He总双电子复合速率系数和态-态双电子复合速率系数,给出了Ti、Cr类He态-态双电子复合速率系数与旁观主量子数、与原子实耦合对称性,以及与谱项多重性、对称性和角动量之间的关系.计算结果显示1s2pnp→1s2np和1s2pnd→1s2nd两衰变通道的双电子复合速率系数占总双电子复合速率系数的75%,成为对总双电子复合速率系数贡献最大的两个复合通道.本文得到了能用于冕区等离子体诊断目的的Ti、Cr类 He双电子复合数据.     

Theoretical study of the KLL dielectronic recombination for highly charged iodine ions

With a developed program for calculation of dielectronic recombination (DR) process, which is based on multi-configuration Dirac-Fock (MCDF) method, the KLL DR processes of the highly charged helium-like to carbon-like iodine ions have been studied systematically. The contributions to doubly excited states from quantum electrodynamic (QED) and Breit effects have been discussed. The KLL DR resonant energies and corresponding resonant strengths have been calculated. The behavior of KLL resonant strengths with increasing Z are analyzed for He-like ions in particular. The theoretical DR spectra for each highly charged ion species are obtained in the KLL region. Comparison has been made between the present calculations and the latest experiments in Tokyo-EBIT.