类氢He+、Li2+离子的电子碰撞强度的R矩阵计算

利用R矩阵方法计算了电子与He+离子碰撞的1s-2s和1s-2p跃迁的碰撞强度,结果表明包括10个靶态的计算可以得到精确的类氢离子的n=1→n=2各能级跃迁的碰撞强度,并首次利用R矩阵方法计算了电子与Li2+离子碰撞的1s-2s和1s-2p跃迁的碰撞强度.     

Radiative rates and electron impact excitation rate coefficients for H-like Fe XXVI

In this paper we report on calculations on energy levels, radiative rates, collision strengths, and effective collision strengths for transitions among the lowest 36 levels of the n≤6 configurations of H-like Fe XXVI. Flexible atomic code (FAC) is adopted for the calculation. Energy levels and radiative rates are calculated within relativistic configuration-interaction method. Direct excitation collision strength is calculated using relativistic distorted-wave approximation. Resonance contributions through the relevant He-like doubly excited n^′l^′n^″l^″ configurations with n^′≤7 and n^″≤75 are explicitly taken into account using the isolated process and isolated resonances approximation. We present the radiative rates, oscillator strengths, and line strengths for all electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) transitions among the 36 levels. Furthermore, collision strengths and effective collision strengths are reported for all the 630 transitions among the above 36 levels over a wide energy (temperature) range up to 25 keV . Extensive comparisons are made with earlier available results and the accuracy of the data is assessed.     

Collision-strength dependence of solar emission lines of Si(X) and S(XII)

We have calculated the normalized populations of 15 levels in Si(X) and S(XII) ions in an optically thin medium, under steady-state condition, by using (i) constant collision strengths computed at the incident electron energy kT_e and (ii) incident electron-energy-dependent collision strengths. To calculate intensity ratios for solar emission lines, one may use constant collision strengths at the electron energy E'.     

Weighted oscillator strengths and lifetimes for the Si XII and Si XIII spectra

The weighted oscillator strengths (gf) and the lifetimes for Si XII and Si XIII presented in this work were carried out in a multiconfiguration Hartree-Fock relativistic (HFR) approach. In this calculation, the electrostatic parameters were optimized by a least-squares procedure, in order to improve the adjustment to experimental energy levels. This method produces gf-values that are in better agreement with intensity observations and lifetime values that are closer to the experimental ones. In this work we present all the experimentally known electric dipole Si XII and Si XIII spectral lines.     

Spectroscopic strengths for 6Li-induced alpha-particle transfers on 24Mg

²⁴Mg(⁶Li, d) angular distributions for transitions to low-lying states in ²⁸Si are well fitted by exact finite-range DWBA calculations and yield relative spectroscopic strengths in good agreement with theoretical predictions as well as with the corresponding results from other α-particle transfer reactions.     

类Na离子振子强度的相对论效应

 采用相对论和非相对论原子自洽场方法,计算了类Na离子（原子序数为11~92）的3s-np,3p-ns和3p-nd跃迁过程的激发能和光学振子强度;通过比较相对论与非相对论的结果,研究了M壳层电子的相对论效应随原子序数的变化规律。结果表明：对n=3的跃迁过程,相对论效应主要是影响激发能,对线强度(或跃迁矩阵元)的影响不重要;对于n>3的跃迁过程,相对论效应同时影响线强度和激发能,通常对线强度的影响更大。这些结果对惯性约束聚变和X射线激光研究中需要的不透明度参数计算有重要的参考意义。     

Phonon effects on oscillator strengths and ƒ-sum of a defect center

We first propose a simple method to deal with the electron-phonon interaction for all states involved in optical transitions and then use the results obtained to derive the equations of the oscillator strengths ? and ?-sum for a defect center including the phonon effects adequately. The derived results are applied to the F center in KCl and discussed in relation to those excluding the dynamical phonon effect.     

Theoretical ionization energies and oscillator strengths for carbon

Frozen core Hartree-Fock wave functions have been calculated for 98 excited s-, p- and d-levels of C(I), and employed to calculate electric dipole oscillator strengths for all allowed transitions between these levels. The energy levels generally agree with observations to within 1.3% and the length and velocity forms of the calculated л-values agree well except for very weak transitions.     

(p, γ) Resonance strengths in the s-d shell

The strengths of selected resonances in the range E_p = 0.5–2.0 MeV in the (p, γ) reactions on Mg, ³⁰Si, ³⁴S, ³⁷C1, ³⁹K and ⁴⁰Ca have been found relative to the E_p = 632 and 992 keV resonances in ²⁷Al(p, γ)²⁸Si by relative yield measurements. Targets were made from mixtures or chemical compounds such that each contained at least two of the isotopes of interest and their chemical composition was determined by Rutherford back-scattering of α-particles. Absolute measurements were conducted on the selected resonances in ²⁷A1(p, γ)²⁸Si and ³⁰Si(p, γ)³¹P by semi-thick target and thin target techniques with the target thickness, needed for the latter technique, found by Rutherford back-scattering of protons. Absolute strengths for all of the resonances treated, together with one from each of ²³Na, ³¹P and ³⁵Cl, reported in a previous paper, were deduced by normalizing to the absolute measurements on the Al(p, γ)²⁸Si resonances.     

Effective collision strengths among the fifteen lowest states of FeXVII

Collision strengths have been calculated for electron impact excitation of neon-like Fe XVII for all transitions within its 15 lowest states. Configuration interaction wavefunctions have been used to represent the target states. The standardR-matrix code has been used to calculate the contribution from the lower scattering partial waves (L⩽9), while the no exchange version of the same code has been used to compute efficiently the contribution of higher partial waves (L⩾10). Effective collision strengths for all the 105 transitions are tabulated for elected temperatures in the range logT _e=5.40 to logT _e=7.00 withT _e expressed in °K.     

Fine-structure splitting calculation in the Ar III ion: comparison of perturbative (Breit-Pauli) and non-perturbative (MCDF-EAL) predictions

We have calculated fine structure splitting in the Ar III ion using the R-matrix method. Two independent atomic structure calculations have been performed. Results from the Breit-Pauli ?C and the Dirac-Atomic ?C R-matrix relativistic calculations are analysed comparatively. Cross sections and collision strengths are provided for selected weak and intercombination transitions, allowing explicitly for resonance effects. Convergence of the partial wave expansion is ensured by examining the partial collision strengths at collision energies up to 20 Ry. Radiative data are also reported here. We discuss all these results and compare them, when possible. For the allowed transitions, for which the resonance structure is not dominant, the two calculations are nearly identical.     

Hartree-Fock line strengths for the lithium,sodium and copper isoelectronic sequences

Hartree-Fock line strengths have been computed for the lowest Δn=0 transitions of ions in the lithium, sodium and copper isoelectronic sequences. Excitation energies were collected relativistically to lowest order in the Pauli approximation, and line strengths were corrected semiempirically using the Dirac correction factors of hydrogen-like ions. Systematic trends have been established and new data are presented for very highly ionized species.     

Theoretical oscillator strengths for some transitions in P(III), As(III), Sb(III) and Bi(III)

Relativistic as well as non-relativistic oscillator strengths have been calculated for transitions in the principal sharp and diffuse series of P(III), As(III), Sb(III) and Bi(III) spectra. The radial integrals were computed by employing the wave functions obtained from a semiempirical method which included exchange effects. A comparison is presented for our calculated f_ik values with experimental and other theoretical data. The influence of relativistic effects on oscillator strengths for transitions in the P(III) through Bi(III) homologous sequence is discussed.     

Total Gamow-Teller strengths from measured ground-state correlations

Recently developed sum rules for Gamow-Teller transitions as observed in (p, n) and (n, p) reactions were applied to all stable even-even target nuclei between ¹⁶O and ⁵⁸Ni and to ⁹⁰Zr. The total Gamow-Teller strengths S(p, n) and S(n, p), which depend sensitively on ground-state correlations, were calculated by the use of measured occupation numbers deduced from proton- and neutron-pickup and stripping experiments. The results are at variance with experimental observations.     

Theoretical term energies and oscillator strengths for carbon

Thomas-Fermi-Hartree-Fock wave functions have been calculated for nl-terms of carbon C(I) (n≤10 and l≤3) and employed to calculate electric dipole oscillator strengths for all allowed transitions between these terms. The dipole length and velocity form of the calculated f-values agree well with the available measurements.     

Line strengths and lifetimes for Kr II

Relative line strengths have been calculated for transitions between states of the 4p ⁴ 5p and 4p ⁴ 5s configurations in Kr II. The wavefunctions are obtained in intermediate coupling, including an effective correction for configuration interaction. Absolute values for the line strengths are determined using the coulomb approximation. Lifetimes for the upper 4p ⁴ 5p levels are given together with available experimental results for comparison.     

Collision strengths for the N = 2 excitation of hydrogenic ions

An empirical formula is given for the estimation of the collision strengths for electron impact excitation of the 2s and 2p states of hydrogenic systems based on close coupling calculations. The coefficients in this formula are given as functions of the nuclear charge, Z, thereby making a possible estimation of the collision strength for any system between H and Fe²⁵⁺.     

Excitation of high-spin particle-hole states in A = 28 nuclei by 27Al(α, t) and (α, 3He) reactions

The ²⁷Al(α, t) and (α, ³He) reactions have been measured at E_α = 64.5 MeV. The experimental angular distributions were analyzed by the exact finite-range DWBA calculations assuming a nucleon stripping mechanism. The distributions of spectroscopic strengths for the single-particle transitions with transferred angular momenta l = 0, 1, 2, 3 and 4 have been obtained. The strengths for the transitions to the stretched 6^? states in ²⁸Si and ²⁸Al are compared to those obtained from inelastic scattering on ²⁸Si. The present results show no distinctive differences in the structures for 6^?T = 0 and 1 states in ²⁸Si such as are observed in proton and pion inelastic scattering on ²⁸Si.     

Electron impact excitation of highly charged sodium-like ions

Oscillator strengths, transition probabilities and collision strengths for transitions between n = 3 and n = 4 levels in Ca(X), Fe(XVI), Zn(XX), Kr(XXVI) and Mo(XXXII) have been calculated in a non-relativistic approximation. Wave functions of excited states have been obtained using a semi-empirical procedure. Collision strengths for electron-impact excitation have been calculated in a distorted wave approximation without exchange.Relative intensities of certain emission lines in the sodium isoelectronic sequence are density dependent. An example of this dependence is discussed in the text.     

Multiplet strengths of excited transitions of Ne sequence

Absolute multiplet strengths of transitions between 2p⁴3p-2p⁴3d terms of Ne⁺ sequence have been obtained by the nuclear charge expansion method within the Hartree-Fock approximation and with mixing of terms of different L-S geneology. Comparison is made with known results for NaIII.