Dipole Polarizabilities of the Ground States for Berylliumlike Ions

Dipole polarizabilities of the ground states for berylliumlike ions with nuclear charge Z = 4 to 10 are calculated by using the Rayleigh-Ritz variational method with multiconfiguration interaction wave functions. The representative models of convergence are listed and compared with other theoretical data for nuclear charge Z = 4 to 6. The present dipole polarizabilities are in good agreement with previous accurate theoretical values available in the literature. For results with greater nuclear charge number, the present calculations may provide benchmarked data for future theoretical and experimental studies. Dynamic dipole polarizabilities of the ground state for the beryllium atom at selected frequencies are also calculated and compared with other theoretical values in the literature.     

类锂离子(Z=11～20)1s23p-1s2nd(n=6,7)的跃迁能和振子强度

用全实加关联(FCPC)方法计算类锂离予体系(Z=11～20)1s2nd(n=6,7)态的非相对论能量.相对论及质量极化效应对能量的修正用微扰论计算,量子电动力学(QED)修正利用有效核电荷方法估算.在此基础上计算了1s23p-1s2nd(n=6,7)的跃迁能及振子强度,对现有的关于1s2nd(n=6,7)态的精细结构的实验数据的可靠性提出质疑.     

类镍X光激光研究中的原子参数讨论

 对可能作为X光激光工作介质的47≤Z≤75及Z=41、79各元素的类镍离子, 系统计算了能级结构及各种过程参数。通过对已有部分实验数据的比较、拟合, 给出了对电子关联校正过的激光波长数据。分析了长波长与短波长激光线振子强度随电荷数的变化规律及其相互竞争关系。以类镍钕离子为例, 分析了粒子数反转及谱线放大对各种过程参数的条件要求并讨论了其它几条重要谱线不能产生增益的原因。     

高离化类锂原子体系(Z=21～30)1s23p态的能级结构和振子强度

用全实加关联方法计算了类锂原子体系(Z=21～30)偶极跃迁1s22s -1s23p的跃迁能、振子强度以及1s23p态的精细结构劈裂.非相对论能量用Rayleigh -Ritz变分法确定;相对论修正和质量极化效应用微扰论计算;同时考虑了来自量子电动力学(QED)效应的修正.得到的理论结果与实验数据及物理规律符合的很好.     

类锂离子(Z=11～20) 1s22s-1s23p的跃迁能和振子强度

用全实加关联方法计算类锂离子(Z=11～20)偶极跃迁1s22s*"2S-1s23p*"2P1/2,3/2的跃迁能.非相对论能量用Rayleigh-Ritz变分法确定,相对论修正和质量极化效应用微扰论计算,还估算了来自量子电动力学效应的修正.得到的计算结果与现有的实验数据符合得很好,我们关于氯的类锂离子(Z=17)1s23p态的精细结构劈裂的计算结果揭示,相应的实验数据明显偏离等电子序列的物理规律.还算了1s22s-1s23p偶极跃迁的振子强度.     

原子核体积效应对类锂离子体系基态能量的修正

用全实加关联的方法得到类锂离子15~22s(Z=21～30)波函数,给出了原子核体积效应公式,计算了原子核的体积效应及质量效应对类锂离子能级的修正.结果显示。在中等大小的核电核情形,原子核体积效应对类锂离子能级的修正要比质量效应对类锂离子能级的修正要显著;随着核电核数的增加,原子核体积效应越来越重要.     

原子核体积效应对类锂离子体系基态能量的修正

用全实加关联的方法得到类锂离子1s22s（Z=21~30）波函数, 给出了原子核体积效应公式, 计算了原子核的体积效应及质量效应对类锂离子能级的修正. 结果显示, 在中等大小的核电核情形, 原子核体积效应对类锂离子能级的修正要比质量效应对类锂离子能级的修正要显著; 随着核电核数的增加, 原子核体积效应越来越重要.     

Effect of density on the equilibrium charge distribution of carbon and oxygen ions

Theoretical estimation of the equilibrium charge distribution of carbon and oxygen ions passed through a matter is obtained. The coefficient considering the effect of density on the charge distribution of these ions is calculated for an amorphous medium consisting of atoms with the nuclear charge Z _t (Z _t ≤ 54). An oscillating dependence of the average ion charge on the nuclear charge of the target atom is obtained which cannot be described by empirical relations.     

Calculation and extrapolation of oscillator strengths in Rb-like,multiply charged ions

The oscillator strengths of dipole transitions between energy levels of the lowest configurations of ions of the Rb I isoelectronic sequence with nuclear charge Z=41–46 are calculated on the basis of the model potential method using an energy approach. For certain ions the reported data are published here for the first time. It is shown that the contribution of core polarization to the oscillator strength attains 15% for some transitions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 89–92, January, 1996.     

Energy loss of light ions with allowance for the presence of metastable particles in the ion beam

The change in the average ion charge due to the presence of particles in metastable states in beams of helium-like ions has been studied. The charge distributions and average charges have been calculated for ions with nuclear charges Z = 3?7 and a velocity of 3.65 au in nitrogen. The previously obtained data on the cross sections of loss and capture of electrons by metastable ions and ions in the ground state were used in the calculations. It is shown that the presence of metastable particles in ion beams leads to an increase in the average charge and energy loss for all considered ions.     

Effective nuclear charge approximation for free rare-earth ions

A semi-empirical method to describe the electron structure of free many-electron rare-earth ions has been proposed. The method takes into account the spin–orbit interaction as well as relativistic interactions known as Breit’s terms. It is shown that a set of parameters to calculate the electronic spectrum of a free rare-earth ion with accuracy less than 5% can be limited to an effective nuclear charge of the rare-earth ion and a constant related to the Breit’s terms. Using the known experimental spectra of free rare-earth metals these parameters have been calculated for basic terms of all rare-earth ions.     

Relativistic calculations of one-photon transition probabilities in hydrogen-like ions

The one-photon transition probabilities in hydrogen-like ions are calculated for nuclear charge numbers in the range 1 ≤ Z ≤ 100. The calculations are performed in the framework of the relativistic Dirac’s theory for the states with the principal quantum numbers n = 2,3, 4. The finite nuclear size effect is taken into account. The role of the quantum electrodynamics (QED) and nuclear recoil corrections is also considered.     

Charge distribution of nitrogen ions reflected from copper and graphite surfaces

A method for the theoretical estimation of the equilibrium charge distribution of ions passed through a media is proposed. It is based on the correction of charge-exchange cross sections for gases using a factor taking the density effect into account. The calculated charge distribution of N ions in graphite agrees well with the existing experimental data. This method makes it possible to estimate the charge distribution of fast N ions reflected from a Cu surface.     

Energy loss of charged particles in matter

A new method of determining the differential energy loss of charged excited nuclei in matter is described. The method is based on the velocity dependence of the Doppler shift of the gamma quanta emitted by moving nuclei. No theoretical assumptions concerning the velocity dependence of atomic or nuclear collisions are necessary. The method and mathematical analysis, described in detail, are applied to the energy loss of Li ions emitting gamma quanta of 477 keV in the kinetic energy range between 100 and 800 keV. It is found that the energy loss of Li ions is linearly proportional to the velocity within 2% for several substances ofZ=1 to 74. The small limits of error, which can be obtained, allow an application of this method to questions as e.g. theZ-dependence of the stopping power on the nuclear charge of the stopping material, chemical binding effects, the time dependence of the adjustment of the equilibrium charge of the projectile after nuclear reactions, or the determination of nuclear angular correlations.     

Muon-pair creation by two x-ray laser photons in the field of an atomic nucleus

The generation of muon-antimuon pairs is calculated in the collision of an ultrarelativistic bare ion with an intense x-ray laser beam. The reaction proceeds nonlinearly via absorption of two laser photons. By systematic study throughout the nuclear chart, we show that the interplay between the nuclear charge and size, along with the possibility of nuclear excitation leads to saturation of the total production rates for high-Z ions, in contrast to the usual Z2 scaling for pointlike projectiles. The process is experimentally accessible by combining present-day ion accelerators with near-future laser sources and in principle allows for the measurement of nuclear form factors.     

Calculation of photon angular distribution and polarization for radiative recombination for highly charged helium-like ions

A systematic study is carried out on the angular distribution and polarization of photons emitted following radiative recombination of He-like ions by a non-relativistic dipole approximation. In order to incorporate the screening effect due to inner-shell electrons, a distorted wave approach is used. The dependence of the calculated angular distribution and polarization on the reduced-energy and nuclear charge are fitted by the corresponding empirical formulas, respectively.     

Multicomponent approximation for evaluation of nonequilibrium charge fractions of ions passing through thin films

A method is proposed to calculate the nonequilibrium charge fractions and mean charges of light ions, depending on film thickness. The calculated results are presented for three charge fractions of 0.75 MeV/nucleon B ion beam, passing through the organic film, and for four charge fractions of 2 MeV/nucleon Ne beam, passing through the carbon film. The dependence of energy loss on the initial charge of projectile Ne ions and target thickness in the nonequilibrium conditions is examined.     

Double ionization of lithiumlike ions by Compton scattering of high-energy photons

The double ionization of lithiumlike ions by Compton scattering of photons is investigated in the asymptotic high-energy region. To leading order of the nonrelativistic perturbation theory, the total cross section for double Compton effect is calculated, taking into account the channels of simultaneous and sequential emission of two electrons. Relationships between the cross sections for double ionization of He- and Li-like ions with the same nuclear charge Z are established. This can open wide perspectives for experimental investigations of ionization processes involving low-lying excited states. The universal scaling is found for the ratio of double-to-single ionization in the lithium isoelectronic sequence.     

Calculation of photon angular distribution and polarization for radiative recombination for high-charged hydrogen-like ions

In this paper a systematic study is carried out on the angular distribution and polarization of photons emitted following radiative recombination of H-like ions by a non-relativistic dipole approximation. In order to incorporate the screening effect due to inner-shell electrons, a distorted wave approach is used. The dependences of the calculated angular distribution and polarization on the reduced energy and nuclear charge are fitted by the corresponding empirical formulas respectively.     

X ray spectroscopic intercomparison between hydrogenic ions of different Z as a method for determining Lamb shifts

Novel methods for determining the 1s Lamb shift of hydrogenic ions are outlined. In one method the energy of a 2–1 transition in the hydrogenic ion of nuclear charge Z is compared to a 4–2 transition in the hydrogenic ion of charge 2Z. A second method exploits close coincidences between Lyman series transitions in ions of similar Z. This revised version was published online in August 2006 with corrections to the Cover Date.