Orbital electron capture decay of hydrogen- and helium-like Pm ions

The β⁺${\beta }^{+}$ and orbital electron-capture decays of stored hydrogen- and helium-like ¹⁴²Pm ions have been measured. So far, such measurements have been performed with only one nucleus, namely ¹⁴⁰Pr. The electron-capture decay constant of hydrogen-like ¹⁴²Pm⁶⁰⁺ ions is about 50% larger than that of helium-like ¹⁴²Pm⁵⁹⁺ ions, which is in excellent agreement with the previous measurements in ¹⁴⁰Pr ions and with new theoretical predictions.     

Orbital Electron Capture Rate and Time Modulation of H- and He-like Ions in a Storage-Ring

We have studied in a heavy ion storage ring the orbital electron capture decays of H- and He-like ¹⁴⁰Pr and ¹⁴²Pm ions and found that the H-like ions with one electron in the K-shell decay 1.49(8) and 1.44(6) times faster, than the corresponding He-like ions with two electrons in the K-shell. This result is explained by spin statistics due to the hyperfine structure of the H-like ions.     

Hyperfine structure of highly charged 23892U ions with rotationally excited nuclei

The hyperfine structure (hfs) of electron levels of 23892U ions with the nucleus excited in the low-lying rotational 2(+) state with an energy E(2(+)) = 44.91 keV is investigated. In hydrogenlike uranium, the hfs splitting for the 1s(1/2) ground state of the electron constitutes 1.8 eV. The hyperfine-quenched (hfq) lifetime of the 1s2p 3P0 state has been calculated for heliumlike 23892U and was found to be 2 orders of magnitude smaller than for the ion with the nucleus in the ground state. The possibility of a precise determination of the nuclear g(r) factor for the rotational 2(+) state by measurements of the hfq lifetime is discussed.     

The decay of140Pr to levels in140Ce

The decay of¹⁴⁰Pr was investigated by means of a Ge(Li) spectrometer. Excited states of¹⁴⁰Ce at 1,596.2, 1,903.1, 2,348.9, 2,522.5, 3,016.8 and 3,119.6 keV are fed in the beta decay of¹⁴⁰Pr. Spin and parity assignments for all observed levels have been made from electron capture and positon disintegration considerations and gamma branches. The experimental level scheme of¹⁴⁰Ce is compared with the results of shell model calculations forN=82 nuclei.     

Time modulation of the beta{+}-decay rate of H-like 140Pr58+ ions

Recent experimental data at GSI on the rates of the number of daughter ions, produced by the nuclear K-shell electron capture (EC) decays of the H-like ions 140Pr58+ and 142Pm60+, suggest that they are modulated in time with periods T_{EC} approximately 7 sec and amplitudes a_{EC} approximately 0.20. Since it is known that these ions are unstable also under the nuclear positron (beta;{+}) decays, we study a possible time dependence of the nuclear beta;{+}-decay rate of the H-like 140Pr58+ ion. We show that the time dependence of the beta;{+}-decay rate of the H-like 140Pr58+ ion as well as any H-like heavy ions cannot be observed.     

Two-body beta decay of stored few-electron ions

The combination of the projectile fragment separator FRS and the cooler-storage ring ESR at the accelerator facility of GSI Darmstadt offers the unique opportunity to study beta decay of stored highly-charged ions. Basic nuclear properties such as masses and half-lives are measured by applying the mass- and time-resolved Schottky Mass Spectrometry (SMS). The relative mass-to-charge ratio is directly correlated to the relative revolution frequency. The SMS is sensitive to single stored ions and the decay of each stored ion can be precisely determine by steady monitoring of the corresponding revolution frequencies. On this basis the single particle decay-spectroscopy has been developed which allows for an unambiguous time-resolved and background-free identification of a certain decay branch. In this contribution we discuss experiments on the orbital electron capture (EC) of radioactive ions in the ESR. Fully ionized, hydrogen- and helium-like ¹⁴⁰Pr and ¹⁴²Pm ions have been selected for these studies. These nuclei decay to stable daughter nuclei via either the three-body ?? ^?+?- or the two-body EC-decay by a single allowed Gamow?CTeller (1^?+? ??0^?+?) transition.     

Application of radiative electron capture for the diagnostics of spin-polarized ion beams at storage rings

It is proposed to apply the radiative electron capture into high-Z projectiles as a probe process for measuring the spin polarization of the hydrogenlike ions at storage rings. We argue that such polarization measurements are possible since the linear polarization of emitted x-ray photons is greatly sensitive to the spin states of incoming ions with nuclear spin I > 1/2. In particular, for K-shell electron capture into the hydrogenlike ions, the linear polarization of light as measured out of the reaction plane is found to be proportional to the degree of ion polarization. Detailed computations for the dependence of the photon polarization on the ion spin states and projectile energies are carried out for the electron recombination into hydrogenlike Bi 82+ ions.     

GSI anomaly and spin–rotation coupling

We propose a model in which a recently reported modulation in the decay of the hydrogenlike ions ¹⁴⁰Pr⁵⁸⁺, ¹⁴²Pm⁶⁰⁺ and ¹²²I⁵²⁺ arises from the coupling of rotation to the spin of electron and nucleus. The model shows that the spin–spin coupling of electron and nucleus does not contribute to the modulation and predicts that the anomaly cannot be observed if the motion of the ions is rectilinear, or if the ions are stopped in a target. It also supports the notion that the modulation frequency is proportional to the inverse of the atomic mass and that no modulation is expected for the β⁺${\beta }^{+}$-decay. The model predicts that for He-like ions the modulation is still present.     

Lyman- alpha(1) decay in hydrogenlike ions: interference between the E1 and M2 transition amplitudes

For the Lyman- alpha(1) transition (2p(3/2)-->1s(1/2)) in hydrogenlike ions an interference between the leading E1 decay channel and the much weaker M2 multipole transition gives rise to a remarkable modified angular distribution of the emitted photons from aligned ions. This effect is most pronounced for the heaviest elements but results in a still sizable correction for medium- Z ions. For the particular case of hydrogenlike uranium where the angular distribution of the Lyman- alpha(1) x rays following radiative electron capture has been measured, the former variance with theoretical findings is removed when this E1-M2 interference is taken into account.     

Overview of the current spectroscopy effort on the Livermore electron beam ion traps

An overview is given of the current spectroscopic effort on the Livermore electron beam ion trap facilities. The effort focuses on four aspects: spectral line position, line intensity, temporal evolution, and line shape. Examples of line position measurements include studies of the K-shell transitions in heliumlike Kr³⁴⁺ and the 2s-2p intrashell transitions in lithiumlike Th⁸⁷⁺ and U⁸⁹⁺, which provide benchmark values for testing the theory of relativistic and quantum electrodynamical contributions in high-Z ions. Examples of line intensity measurements are provided by measurements of the electron-impact excitation and dielectronic recombination cross sections of the heliumlike transition-metal ions Ti²⁰⁺ through Co²⁵⁺. A discussion of radiative lifetime measurements of metastable levels in heliumlike ions is given to illustrate our time-resolved spectroscopy techniques in the microsecond range. We also present a measurement of the spectral lineshape that illustrates the very low ion temperatures that can be achieved in an EBIT.     

电离度效应对高电离态类氢离子平均寿命的影响

利用类氢离子新势函数模型,研究了电离度效应对高电离态类氢离子平均寿命的影响,计算了类氢Kr+35离子2p-8p态的平均寿命.发现电离度效应使类氢O+7-Pm+60离子各态的平均寿命相对减少0.26%～9.41%.结果对估价高电离态原子光谱和寿命的测量值有一定影响,有利于识别离子状态.     

中低能速度能区离子与H,He原子碰撞中的经典电子俘获截面

Bohr-Lindhard模型被用来描述中低能速度能区离子—原子碰撞中的经典电子俘获过程。根据离子与原子的作用时间与碰撞参数的关系,建立俘获几率对碰撞参数的依赖性,碰撞参数范围被限定在俘获半径之内。在该模型的框架内,人们试图通过电子的空间分布函数来研究所有碰撞参数的贡献,但存在较为复杂的数值计算。基于Bohr-Lindhard模型,本工作提出通过简单的指数衰减函数来描述电子俘获几率对碰撞参数的依赖性,计算了Aq+(q = 2~6)-H碰撞中的单电子俘获截面和Aq+(q = 3~6)-He碰撞中的双电子俘获截面,计算结果与已有实验数据符合很好,很好地描述了低能和中能区的电子俘获截面随能量和电荷态的变化,该工作还可计算其他不同电荷态离子与He和H靶的电子俘获截面。     

Z箍缩等离子体K壳层X射线自辐射单色成像

采用针孔配接对数螺线柱面晶体方案,研制了一种小型、靶室内置X射线单色成像器,用于获取Z箍缩等离子体K壳层自辐射单色图像。在阳加速器上对该成像器进行了测试,成功地获取了铝丝阵负载Z箍缩等离子体K壳层自辐射的类氢线与类氦线单色图像。实验结果表明:该成像器具有优异的单色性（能谱带宽小于1 eV）,适合于中低原子序数Z箍缩内爆负载的特征谱线单色图像诊断。     

原子实对离子n壳层辐射复合截面的影响

基于Dirac-Slater相对论平均自洽场理论和类氢模型,研究了自由电子被辐射复合到裸核和类裸核离子的n壳层时RR截面随自由电子能量的变化,以及原子实对这种变化的影响;给出了两种理论模型下RR截面曲线变化的差异,并对这种差异做了较详细的理论说明.     

Pr,Yb:ZBLAN上转换发光过程中的能量传递

详细地研究了Ｐｒ３＋，Ｙｂ３＋ＺＢＬＡＮ玻璃中Ｐｒ３＋和Ｙｂ３＋离子之间的能量传递过程、及能量传递对上转换发光的影响。实验结果表明，在９６０ｎｍ激光泵浦下Ｙｂ３＋通过Ｙｂ３＋—Ｐｒ３＋之间的交叉弛豫向Ｐｒ３＋传递能量。具体的能量传递形式有三种。Ｙｂ３＋作为敏化剂可提高Ｐｒ３＋的上转换发光强度。从Ｐｒ３＋向Ｙｂ３＋的反向能量传递过程也是存在的，具体的过程和Ｐｒ３＋向Ｙｂ３＋传递的相反。Ｐｒ３＋—Ｙｂ３＋的能量传递导致Ｐｒ３＋发光的淬灭，使Ｐｒ３＋上转换发光随着Ｙｂ３＋浓度增加出现饱和。和３Ｐ０能级相比较，Ｙｂ３＋对Ｐｒ３＋离子的１Ｄ２能级发光的淬灭作用更强     

Observation of non-exponential orbital electron capture decays of hydrogen-like Pr and Pm ions

We report on time-modulated two-body weak decays observed in the orbital electron capture of hydrogen-like ¹⁴⁰Pr⁵⁹⁺ and ¹⁴²Pm⁶⁰⁺ ions coasting in an ion storage ring. Using non-destructive single ion, time-resolved Schottky mass spectrometry we found that the expected exponential decay is modulated in time with a modulation period of about 7 seconds for both systems. Tentatively this observation is attributed to the coherent superposition of finite mass eigenstates of the electron neutrinos from the weak decay into a two-body final state.     

Inelastic processes in collisions of multicharged fast ions with atoms

We use the eikonal approximation to develop a general formula for the cross sections of inelastic collisions of multicharged fast ions (including relativistic ions) with atoms that is applicable within a broad range of collision energies, has the standard nonrelativistic limit, and becomes, in the ultrarelativistic case, the well-known result that follows from the exact solution of the Dirac equation. As an example we study the excitation and ionization of a hydrogenlike atom, the single and double excitation and ionization of a heliumlike atom, and multiple (up to the eighth order) ionization of the neon atom and (up to eighteenth order) ionization of the argon atom. We derive simple analytical expressions for the inelastic cross sections and establish recurrence relations linking the cross sections of ionization of different orders. Finally, we compare our results with the experimental data. Zh. éksp. Teor. Fiz. 114, 1646–1660 (November 1998)     

Peculiarities in the cross sections of electron capture by phosphorus ions

The effect of decreasing the cross sections of electron capture by phosphorus (P⁵⁺) ions penetrating through gaseous media has been revealed experimentally. This effect is a violation of the known uniform dependence between the electron-capture cross section and the ion charge. Such an anomaly was not observed in measurements performed with argon ions under the same conditions. A possible reason of decreasing the cross sections of electron capture by P⁵⁺ ions may be autoionization of excited P⁴⁺ ions. The latter are formed during electron capture into excited states by metastable particles of a beam of P⁵⁺ ions.     

pr3+ 激活的CaMoO4红色荧光粉的发光性质

采用高温固相法制备了稀土pr3+激活的Ca1-xPrxMoO4(0.005≤x≤0.02)系列红色荧光粉.荧光光谱表明:在453 nm激发下,样品产生了红光发射,其中对应于pr3+的特征跃迁3 P0→3F2位于654 nm的红色发射峰最强.分析了pr3的掺杂摩尔分数x对样品发光强度的影响,确定pr3+的最佳掺杂摩尔分数...