Autoionization spectra of Sm atom

Spectra of autoionizing states of the Sm atom in an energy region between 45948.9 cm-1 and 46943.6 cm-1 are systematically investigated by a three-color multi-step resonant excitation scheme with three different excitation paths.The three intermediate states,4f 66s7s 7F3,4f 66s7s 7F4,and 4f 66s7s 9F5 are employed for the three paths,respectively.Based on precise calibration of wavelength,the level energies of 112 autoionizing states are determined with the line widths and the relative line intensities of the related transitions.The possible influence of configuration interaction on the line shape of autoionizing state is also discussed.In addition,a unique value of J,the total angular momentum,is assigned to all detected states by comparing the three spectra obtained with the different excitation paths.     

Autoionization cross section of potassium atom excited by electron impact

The autoionization cross section of potassium atoms excited by electron impact is measured in the energy range from the first autoionization threshold at 18.72 eV to 202 eV. The data are obtained by deter-mining the total intensity of electron spectra resulting from the decay of the 3p ⁵ n ₁ l ₁ n ₂ l ₂ autoionizing states. The cross section has two maxima, 1.8 × 10^?16 and 2.2 × 10^?16 cm², at 21 and 32 eV, respectively. The excitation dynamics of autoionization states suggests that the first maximum is associated with the resonance character of the near-threshold excitation. The second maximum, as well as the behavior of the cross section at energies above 50 eV, reflects the dynamics of electron excitation of quartet and doublet autoionizing states. The measured autoionization cross section is compared with known data for the total single ionization cross section of potassium atom by electron impact. The relative contribution of the autoionization cross section to the total single ionization cross section is found to reach 30% at 32 eV.     

The beryllium atom and beryllium positive ion in strong magnetic fields

The ground and a few excited states of the beryllium atom in external uniform magnetic fields are calculated by means of our 2D mesh Hartree-Fock method for field strengths ranging from zero up to 2.35×10⁹ T. With changing field strength the ground state of the Be atom undergoes three transitions involving four different electronic configurations which belong to three groups with different spin projections S _z = 0, - 1, - 2. For weak fields the ground state configuration arises from the 1s ²2s ², S _z = 0 configuration. With increasing field strength the ground state evolves into the two S _z = - 1 configurations 1s ²2s2p _-1 and 1s ²2p _-13d _-2, followed by the fully spin polarised S _z = - 2 configuration 1s2p _-13d _-24f _-3. The latter configuration forms the ground state of the beryllium atom in the high field regime γ > 4.567. The analogous calculations for the Be ⁺ ion provide the sequence of the three following ground state configurations: 1s^22s and 1s ²2p _-1 (S _z = - 1/2) and 1s2p _-13d _-2 (S _z = - 3/2). Received 2 October 2000 and Received in final form 8 January 2001     

Relativistic and QED corrections for the beryllium atom

Complete relativistic and quantum electrodynamics corrections of order alpha(2) Ry and alpha(3) Ry are calculated for the ground state of the beryllium atom and its positive ion. A basis set of correlated Gaussian functions is used, with exponents optimized against nonrelativistic binding energies. The results for Bethe logarithms ln(k(0)(Be)=5.750 34(3) and ln(k(0)(Be+)=5.751 67(3) demonstrate the availability of high precision theoretical predictions for energy levels of the beryllium atom and light ions. Our recommended value of the ionization potential 75 192.514(80) cm(-1) agrees with equally accurate available experimental values.     

Autoionization states of the positronium negative ion in exponential cosine-screened Coulomb potentials

The 2s^2 1S^e2s^2~^1{\rm S}^e autoionization resonance states of the positronium negative ion (Ps^-) in exponential cosine-screened Coulomb potentials (ECSCP) are investigated using stabilization method. Highly correlated wave functions for Ps^- are used to take into account the correlation effect of the charged particles. Results for resonance energies and widths are reported for the screening parameter in the range 0.0-0.07 (in a₀ ^-1), to the best our knowledge, for the first time in the literature.     

铍原子里德堡能级的计算(英文)

依据最弱受约束电子势模型理论,计算了铍原子1s~22sns~1S_0(n=3～50)、1s~22snp~1P_1~0(n=3～50)_和1s~22snd~1D_2(n=3～50)里德堡系列能级和量子亏损.计算结果与已有的实验结果符合得很好.     

Autoionization in the evolution process of dense Rb Rydberg atoms in nP states

The autoionization mechanisms of dense nP_3/2 (n = 20–97) Rydberg gases of ⁸⁷Rb atoms in the spontaneous evolution were investigated for the first time. By observing the characteristic time of the electrons generated through autoionization process, the dependence of autoionization mechanisms (black-body radiation, electron–Rydberg collision, and Penning ionization) on the principal quantum number n of initial nP states was demonstrated. The dependence on the number n in nP Rydberg atoms is similar to those in nD Rydberg atoms.     

Ground-state energy of beryllium atom with parameter perturbation method

We present a perturbation study of the ground-state energy of the beryllium atom by incorporating double parameters in the atom's Hamiltonian. The eigenvalue of the Hamiltonian is then solved with a double-fold perturbation scheme,where the spin-spin interaction of electrons from different shells of the atom is also considered. Calculations show that the obtained ground-state energy is in satisfactory agreement with experiment. It is found that the Coulomb repulsion of the inner-shell electrons enhances the effective nuclear charge seen by the outer-shell electrons, and the shielding effect of the outer-shell electrons to the nucleus is also notable compared with that of the inner-shell electrons.     

Studies on odd-parity states of the Sm atom

Two-step excitation and ionization processes are used to detect Sm atoms in many excited states populated with tunable lasers. The wavelength of the first laser is tuned to the resonances from the Sm 4f^6 6s^2 ^7FJ （J=0 6） states to many odd-parity states with different electronic configurations, where the atoms are detected by photoionization process using an ultraviolet laser with a wavelength of 355 nm. Precise measurements on the energy level and intensity for many Sm 4f^6 6s6p and 4f^5 5d6s^2 states have been carried out. In a theoretical analysis on the spectral data, such as peak position, relative intensity, many transitions can be identified as the resonances from the Sm 4f^6 6s^2 7FJ （J=0-6） states to the atomic states with 4f^6 6s6p and 4f^5 5d6s^2 electronic configurations. This work also reports many spectral data on the odd-parity states that cannot be found in the literature.     

n维氢原子的散射态

研究了n维氢原子的散射态性质．给出了精确的按“k/2π标度”归一化的散射态的精确解波函数及相移表达式，讨论了相移的解析性质，获得了束缚-连续跃迁矩阵元的解析计算公式．普通氢原子(n=3)散射态的有关结果作为特例包含在本文的一般结论之中． 关键词： n维氢原子 散射态 精确解 相移 束缚-连续跃迁矩阵元     

Image states on beryllium surfaces with low indices

Using the self-consistent pseudopotential method, we have calculated the binding energy of the image states for the (0001) , and surfaces of beryllium. It is shown for the (0001) face that there exists a pronounced resonance image state with n=1 and energy −0.95 eV at the point of the surface Brillouin zone. In the surface, which has a wide band gap in the vicinity of the vacuum level, the calculated image state with n=1 at the point has energy −1.2 eV and is a surface state of gap type. For the face in the vicinity of the point band gaps are absent. However, the symmetry of the bulk states near the vacuum level enables the existence of a resonance image state with n=1 and energy −0.6 eV. Fiz. Tverd. Tela (St. Petersburg) 41, 935–940 (June 1999)     

The study of autoionizing states of the samarium atom

The investigation of the samarium (Sm) atom autoionizing states, belonging to the 4f⁶ 6pnl and 4f⁵ 5d6snl (l=0, 2) configurations, has been carried out by using a three-step isolated-core-excitation (ICE) scheme. Fifty-seven new autoionizing states of the Sm atom have been observed in the energy region between 60,700 and 66,500 cm^?1. These autoionizing states are classified into five autoionization series in the light of different ionization limits. In most cases, the transition profiles of these autoionizing states are nearly symmetric, from which the peak positions and widths can be easily obtained by Lorentzian-profile-fitting procedure. Some autoionizing states have multi-peak profiles whose spectroscopic properties are analyzed in order to understand the complicated structures.     

利用光电离技术研究奇宇称的Sm原子光谱

采用一台频率可扫描的染料激光器将Sm原子从4f66s2 7FJ(J=1,2)态分别激发到具有不同电子组态的若干原子态上,然后利用光电离技术对处于上述状态的Sm原子进行高灵敏探测.通过波长固定在355nm的紫外激光器,我们对一系列具有4f66s6p或者4f55d6s2电子组态的原子状态进行了精密的光谱测量.本实验研究不但确定了这些态的能级位置,还给出了它们的相对光谱强度.通过理论方法对光谱数据详细的分析,我们不但确认了文献中Sm原子的部分奇字称能级的位置和光谱标识,还同时给出了许多新的跃迁及其光谱特性.     

Multistep excitation of autoionizing states of the samarium atom

In this work, 4f ⁶6pnl and 4f ⁵5d6snl (l=0,2) autoionizing states of the samarium (Sm) atom, especially those with lower principal quantum number, have been studied, using the isolated-core excitation scheme with three dye lasers. In the energy region between 57 990 and 61 030 cm⁻¹, there are 74 autoionizing states of the Sm atom observed. These states can be classified into the autoionization series converging to four different ionization limits. In most cases, the line shapes of these autoionizing states are nearly symmetric, from which the level energies and widths can be easily obtained by fitting the experimental spectra to the Lorentzian profiles. In addition, several spectroscopic properties of these autoionizing states, such as configuration interaction, are also discussed.     

Even-parity states of the Sm atom with stepwise excitation

Two-colour stepwise excitation and photoionization schemes are adopted to study the spectra of high-lying states of the Sm atom. These bound even-parity states are excited with three different excitation paths from the 4f66s6p7DJ (J = 1, 2, 3) intermediate states, respectively. They are probed by photoionization process with an extra photon driving them to the continuum states. In this experiment, 270 states are detected in an energy range from 36160 cm-1 to 42250 cm-1, 109 of which are newly discovered, while the rest of them are confirmed to be the energy levels reported previously. Furthermore, based on the J-momentum selection rules of three excitation paths, a unique assignment of J-momentum for all observed states is determined, eliminating all remaining ambiguities in the literature. Finally, 53 single-colour transitions originating from the scanning laser are also identified. For all the relevant transitions, the information about their relative intensities is also given in the paper.     

Double-excited narrow autoionization states of ytterbium atom

We report the results of theoretical and experimental research of double-excited narrow autoionization states of the ytterbium atom near the ionization limit. The energy of autoionization states of the 5d², 6p², 5d6p and 7s6p configurations was calculated. Perturbation theory with a model zero-order approximation was used in this calculation. The autoionization states of the 7s6p configuration were experimentally detected by using the method of multistep laser excitation and ionization of atoms.     

Perturbation of the excited states of the hydrogen atom and hydrogen-like ions by a neutral atom

Owing to the degeneracy of the energy levels, the wavefunction of the electron in the excited states of the hydrogen atom and hydrogen-like ions perturbed by a neutral atom B is significantly different from the wavefunction of the unperturbed state. The perturbed function has a wide high maximum in the region of atom B, which is explained by multiple collisions of the electron with atom B, because the classical trajectories in the Coulomb field are closed and the size of atom B is much smaller than the size of the excited-state orbit. The radiative lifetimes of the excited states are much larger than those of unperturbed states. The orbital angular momentum L of the excited electron is strongly changed in collisions with atom B owing to the quantum interference or mixing of the temporal phases of adiabatic wavefunctions. The cross sections for such a change in the orbital angular momentum are several orders of magnitude larger than the cross sections found in early investigations in the approximation of the single collision of the electron with atom B.