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     

Auger transitions in Li-like and Be-like ions

Measurements of the Auger decay of beam-foil excited Be II and Be I levels are reported along with a proposed assignment of the experimental spectra. The Li I, Be II and Be III (1s2s²)²S → (1s²2s)²S Auger transitions as presented in this letter represents the first observation of such states in positive ions with Z?5.     

Lifetime measurements of ultrashort-lived excited states in Be-like ions

We propose to measure the lifetime of short-lived excited states in highly charged ions by pump-probe experiments. Utilizing two synchronized and delayed Femtosecond pulses allows accessing these lifetimes with Femtosecond precision. Such measurements could provide sensitive tests of state-of-the art atomic structure calculations beyond the capabilities of established methods.     

Lifetime measurements for some levels in Be-like Cl XIV and S XIII

Lifetime measurements have been carried out for some low lying (n = 2) levels in the four-electron ions Cl XIV and S XIII using the beam-foil technique. Accurate oscillator strengths for the 2 s2 ¹ S - 2 s 2 p ¹ P o transition have been determined by the inclusion of prominent cascades in the analysis. Lifetimes of the levels of the 2 p2 ³ P j multiplet have also been measured for both ions. The results are compared with theoretical predictions and earlier measurements. Received: 29 October 1997 / Revised: 10 February 1998 / Accepted: 5 March 1998     

Detection of trielectronic recombination of In<Superscript>+</Superscript> ion

The trielectronic recombination of an In⁺ (4d ¹⁰5s ^{2 1} S ₀) ion in collisions with slow electrons, including the two-electron excitation of the 5s2 core of the ion with the simultaneous capture of the triply excited 5p ³ intermediate autoionizing state with its subsequent radiative stabilization 5p ³ → 5s5p ² + hν has been detected and experimentally examined for the first time. The maximum effective cross section of trielectronic recombination is 1.6 × 10⁻¹⁶ cm², which is comparable to the effective cross sections for both dielectronic recombination and electron excitation of the In⁺ ion.     

A distribution function for angular correlation in He- and Be-like ions

A distribution function for the interelectronic angle in atomic systems is suggested and examined for 2- and 4-electron ions. The correlated wave-functions of Weiss and others were used to study the behaviour and relative importance of angular correlation in the K and L shells.     

类Li和类Be等电子序列离子基组态能量的Z相关修正

在相对论多体微扰理论和屏蔽理论的基础上,本文提出了一种计算等电子序列离子基组态能量的新方法,通过引入一个与核电荷数Z相关的能量修正函数γ(Z)来考虑由于忽略能量的高阶项对原子体系基组态能量的影响。在对类Li(Z=3～50)和类Be(Z=4～50)等电子序列离子的基组态能量所进行的理论计算研究结果表明,Z相关能量修正对于原子体系基组态能量的准确计算是有效的。     

Calculation of the binding energy of a highly excited electron in heavy Be-like ions

The binding energy of a highly excited electron (n=20–50, where n is the principal quantum number) in the Be-like ions Au⁷⁵⁺, Pb⁷⁸⁺, Bi⁷⁹⁺, and U⁸⁸⁺ is calculated in order to determine the energy of the 2p _1/2-2s transition from experiments on dielectronic recombination in Li-like ions. A formula approximating the calculated data with an error not exceeding 0.04% is proposed.     

Energy straggling of Cl ions in gases

Energy-loss distributions for Cl ions in Ar-CH₄ and isobutane were measured at incident energiesE ₀=9.4, 17.1, 27.1 and 39.4 MeV up to relative energy lossesΔE/E ⁰?0.7. The full widths at half maximum are larger than predicted by the Landau-Vavilov-theory by more than a factor two. A semiempirical formula is derived which reproduces well all data measured. Reasonable agreement is obtained between this formula and other energy straggling data of heavy ions reported in the literature.     

Dissociative recombination of highly symmetric polyatomic ions

A general first-principles theory of dissociative recombination is developed for highly symmetric molecular ions and applied to H(3)O(+) and CH(3)(+), which play an important role in astrophysical, combustion, and laboratory plasma environments. The theoretical cross sections obtained for the dissociative recombination of the two ions are in good agreement with existing experimental data from storage ring experiments.     

Stabilization of diatomic products in recombination of heavy ions

We have studied the kinematic conditions for the formation of the most stable products of direct three-body recombination of ions Cs⁺ and Br^? in the presence of a third-body Xe atom. As the energy of the ions?? central encounters and the energy of the third body range from 1 to 10 eV, the minimal residual energy of the recombination products is found to lie in the interval 0?C0.7 eV. The formation of the recombination products with the minimal internal energies is yielded by collisions of the three particles in a triangular configuration in an impact parameter range from 0 to 2.7 a.u. The mutual orientation angles of the vector of the relative ion velocity and the vector of the third body velocity affect the formation of products with the minimal internal energy rather slightly. In most cases, stabilization of the CsBr molecules and high efficiency of the energy transfer to the third body are observed in configurations of the closest approach of the particles with interionic distances close to the equilibrium distance in the CsBr molecule.     

Three-body recombination of ions with electrons in cooler-storage rings

Three-body recombination (TBR) of bare ions with free electrons of anisotropic velocity distribution is discussed in the context of recombination experiments in cooler-storage rings. The recombination rates are derived from the electron impact ionization rates using the modified Saha equation. Analytical expressions for the TBR rates and new scaling rules with main quantum number n, atomic number Z, and both transverse and longitudinal electron temperatures are derived for the low n-states regime probed in experiments in cooler-storage rings. In this context, the discrepancies found between measured rates and predictions for radiative recombination for the e + Ne¹⁰⁺ system [Gao et al., Phys. Rev. Lett. 75 (1995) 4381] are discussed. Present results show that TBR rates for the flattened electron beam velocity distribution cannot account for the recombination enhancement observed at very low relative energies. This revised version was published online in August 2006 with corrections to the Cover Date.     

Dielectronic recombination rate coefficients for hydrogen-like ions

We present rate coefficients for dielectronic recombination for 9 hydrogen-like ions ranging from Ne⁹⁺ to Xe⁵³⁺. In this work, relativistic multi-configuration wavefunctions are used to calculate energy levels as well as the Auger and radiative matrix elements. Results are compared with recent calculations for ions in the helium-like sequence.     

The dynamics of direct three-body recombination of ions

The trajectory simulation of the direct recombination of the Cs⁺ and Br^? heavy ions in the presence of third-body atoms R = Kr, Xe, Hg was performed on the potential energy surface that controlled the dissociation of CsBr induced by collisions with the same R. The results showed that the probability of recombination decreased as the energy of the approach of ions to each other and the energy of a third body with respect to the center of mass of the ion pair increased. Direct recombination proceeds according to at least two mechanisms of the stabilization of the molecule formed. The first mechanism involves the collision of the R atom with both ions at low impact parameters with respect to the center of gravity of the ion pair. In the second mechanism, impact parameters are large, and energy is removed through a collision with one of the ions of the pair. The products formed have a strongly nonequilibrium vibrational distribution and almost equilibrium rotational energy distribution.     

State-selective radiative recombination cross sections of argon ions

The n-, (n,l)- and fine-structure level state-selective radiative recombinations (RR) cross sections of argon ions Ar¹⁸⁺,Ar¹³⁺,Ar⁷⁺ and Ar⁺ are obtained with the semi-classical Kramer formula, the relativistic self-consistent field (RSCF) method and the relativistic configuration interaction (RCI) method. It is found that for the highly charged ions with few electrons, the cross sections calculated with these three methods are in good agreement with each other. But as the number of electrons increases, the Kramer formula deviates from the RSCF and RCI results. For instance, when the energy of the incident electron is larger than 100 eV, the n-state selective cross sections of Ar⁷⁺ calculated from the Kramer formula are underestimated for more than 50%. The RSCF results are in general agreement with the RCI results. However, for the low charged ions, a clear distinction appears due to the strong configuration interaction, especially near the Cooper minimum. The n-resolved (n≤10) and total Maxwellian averaged rate coefficients are calculated, and the analytic fitting parameters are also provided.     

Three-body recombination of atomic ions with slow electrons

Using the time-dependent wave-packets method, we have quantum mechanically investigated the three-body recombination process for electron energies varying from 10 to 0.01 eV. The classical "bottleneck" prediction on the probable population was confirmed by our S-wave quantum calculations for electron kinetic energies (K(E)) as low as 0.1 eV. But for K(E)<0.1 eV, the quantum three-body recombination tends to populate lower n levels than the classical theory predicted. We also find that, in the same n level, the recombination tends to populate higher angular-momentum states with K(E) decreasing. These results may shed light on the intrinsic dynamics of both ultracold plasmas and frozen Rydberg gases.     

Statistical dielectronic recombination rates for multielectron ions in plasma

We describe the general analytic derivation of the dielectronic recombination (DR) rate coefficient for multielectron ions in a plasma based on the statistical theory of an atom in terms of the spatial distribution of the atomic electron density. The dielectronic recombination rates for complex multielectron tungsten ions are calculated numerically in a wide range of variation of the plasma temperature, which is important for modern nuclear fusion studies. The results of statistical theory are compared with the data obtained using level-by-level codes ADPAK, FAC, HULLAC, and experimental results. We consider different statistical DR models based on the Thomas–Fermi distribution, viz., integral and differential with respect to the orbital angular momenta of the ion core and the trapped electron, as well as the Rost model, which is an analog of the Frank–Condon model as applied to atomic structures. In view of its universality and relative simplicity, the statistical approach can be used for obtaining express estimates of the dielectronic recombination rate coefficients in complex calculations of the parameters of the thermonuclear plasmas. The application of statistical methods also provides information for the dielectronic recombination rates with much smaller computer time expenditures as compared to available level-by-level codes.     

Rotational effects in low energy dissociative recombination of diatomic ions

The effect of rotational interaction in the low energy dissociative recombination process of diatomic molecules has been explored for typical molecular ions () which sample a large range of molecular masses. We show that rotation plays a role mainly for the indirect recombination process through bound Rydberg states, and for light molecules. When the direct process based on a strong electronic interaction is fast and dominating, rotational couplings can be safely neglected especially for heavier molecules like NO. Received: 18 September 1997 / Revised in final form: 17 October 1997 / Accepted: 20 October 1997     

Radiative recombination of ions and nuclei in electron cooling systems

Experimental data on rates for the radiative recombination of nuclei (from helium to uranium) and various ions in interaction with an electron beam in electron cooling systems are reviewed. An analysis of the experimental data has yielded the dependence of the radiative recombination rate on the relative electron energy appreciably differently than the theoretical models obtained earlier by H. Kramers and R. Schuch. In addition, it is shown that the radiative recombination rate of nuclei in the experiment depends on the transverse electron energy as T _?? ^?0.82 ,which is also different from the results of the calculations by the theoretical model proposed by M. Bell and J. Bell. Experimental data on the cooling of ions in intermediate charge states are analyzed and the dependence of the radiative recombination rate on the charge state of the ion (electron-shell configuration) is shown. For some ion charge states, the rate of the process is of a resonance character. Loss to radiative recombination in the electron cooling system of the NICA Booster is evaluated for the Au³²⁺, Au³³⁺, Au⁵⁰⁺, and Au⁵¹⁺ ion beams. Limitations imposed on the Au79+ beam lifetime by radiative recombination in the electron cooling system of the NICA Collider are analyzed. Possible ways to decrease the radiative recombination rate of nuclei by selecting the parameters of the electron cooling system for the NICA Collider are proposed.