Radiative lifetimes in Ce I and Ce II

New radiative lifetime measurements based on time-resolved laser-induced fluorescence techniques are reported for 18 even-parity levels belonging to the 4f5d^26p and 4f ²5d ² configurations of Ce I and 6 even-parity levels belonging to the 5d^26s, 4f5d6p, and 4f6s6p configurations of Ce II. Free neutral and singly ionized cerium atoms were produced by laser ablation. The Ce I and Ce II levels range in energy from 26 545 to 29 102 cm^-1, and 42 573 to 48 152 cm^-1, respectively. Received 25 September 2002 Published online 4 March 2003     

Energy levels, oscillator strengths and lifetimes in Ar V

We have calculated the excitation energies, oscillator strengths and transition probabilities for electric-dipole-allowed and intercombination transitions among the 46 LS levels belonging to the configurations 3s ²3p ², 3s3p ³, 3s ²3p3d, 3p ⁴, 3s ²3p4s, 3s ²3p4p, 3s3p ²(² S)4s, 3s3p ²(² P)4s, 3s3p ²(⁴ P)4s, 3s3p ²(² D)4s, 3s ²3p4d and 3s ²3p4f of Si-like Argon. These states are represented by extensive Configuration-Interaction (CI) wavefunctions obtained using the CIV3 computer code of Hibbert. From our transition probabilities we have also calculated the radiative lifetimes of singlet and triplet states of Ar V. Our results are compared with other available theoretical calculations and experimental data. To assess the importance of relativistic effects on our calculated values, we have also carried out calculations in the intermediate-coupling scheme using the Breit-Pauli Hamiltonian. Small adjustments to the diagonal elements of the Hamiltonian matrices have been made so that the energy splittings are as close as possible to the experimentally compiled energy values of the National Institute for standards and Technology (NIST). The energy splitting of 85 fine-structure levels, the oscillator strengths and transition probabilities for electric-dipole-allowed and intercombination transitions and the lifetimes of some fine-structure levels are presented and compared with available experimental and other theoretical values. In this calculation, we also predict new data for several fine-structure levels where no other theoretical and experimental results are available.     

Level lifetimes in 3p and 3d configurations of Fe XII

Transitions between the five fine-structure levels in the 3s ²3p ³ ground configuration of Fe XII (P-like) are of interest in astrophysics and terrestrial plasma diagnostics. The decay rates give rise to level lifetimes in the millisecond range, which have been measured recently at a heavy-ion storage ring. While most of the 3s ²3p ²3d levels are short-lived, two of these levels have no E1 decay channels and may also have millisecond lifetimes. We present HFR and MCDF calculations of the E1, M1, E2 and M2 transition rates between the 3s ²3p ³, 3s3p⁴ and 3s ²3p ²3d levels and compare the lifetime results to most recent experimental data as well as to other predictions. Received 2 October 2001 / Received in final form 22 January 2002 Published online 28 June 2002     

Fine-structure energy levels,oscillator strengths and lifetimes in Mg-like chromium

Excitation energies from ground state for 86 fine-structure levels as well as oscillator strengths and radiative decay rates for all fine-structure transitions among the levels of the terms (1s²2s²2p⁶)3s²(¹S), 3s3p(^1,3P^o), 3s3d(^1,3D), 3s4s(^1,3S), 3s4p(^1,3P^o), 3s4d(^1,3D), 3s4f(^1,3F^o), 3p²(¹S, ³P, ¹D), 3p3d(^1,3P^o, ^1,3D^o, ^1,3F^o), 3p4s(^1,3P^o), 3p4p(^1,3S, ^1,3P, ^1,3D), 3p4d(^1,3P^o, ^1,3D^o, ^1,3F^o), 3p4f(^1,3D, ^1,3F, ^1,3G) and 3d²(¹S, ³P, ¹D, ³F,¹G) of Cr XIII are calculated using extensive configuration-interaction (CI) wave functions obtained with the CIV3 computer code of Hibbert. The important relativistic effects in intermediate coupling are included through the Breit-Pauli approximation via spin-orbit, spin-other-orbit, spin-spin, Darwin and mass correction terms. Small adjustments to the diagonal elements of the Hamiltonian matrices have been made. The mixing among several fine-structure levels is found to be very strong. Our excitation energies, including their ordering, are in excellent agreement (better than 0.5%) with the available experimental results. From our transition probabilities, we have also calculated radiative lifetimes of some fine-structure levels. Our calculated lifetime for the longer-lived level 3s3p(³P₁) is found to be in excellent agreement with the experimental result of Curtis compared to other theoretical calculations.     

Radiative lifetime and oscillator strength determinations in potassium ions (K V, K VI and K VII)

Oscillator strengths have been calculated for the transitions depopulating levels of the 3s²3p³, 3s3p⁴ configurations of K V, of the 3s²3p², 3s3p³ configurations of K VI and of the 3s²3p, 3s3p², 3p³ and 3s3p3d configurations of K VII. A multiconfiguration Dirac-Fock method, incorporating the relativistic two-body Breit interaction and quantum electrodynamics corrections due to self-energy and vacuum polarization, has been used for the calculations. The reliability of this approach has been tested by comparison with relativistic Hartree-Fock calculations and also with some experimental measurements performed by beam-foil spectroscopy at a beam energy of 1.7 MeV.     

Collision strengths for transitions in Ni XIX

In this paper we present calculations of electron impact excitation collision strengths for transitions among the 89 fine-structure levels of the 2s²2p⁶, 2s²2p⁵3ℓ, 2s2p⁶3ℓ, 2s²2p⁵4ℓ, and 2s2p⁶4ℓ configurations of Ni XIX, for which flexible atomic code (FAC) has been adopted. Comparisons are made with the earlier available results in the literature, and the anomalies observed have been discussed.      

类氮KⅩⅢ,CaⅪⅤ,ScⅩⅤ和TiⅩⅥ精细结构能级和跃迁波长的相对论多组态Dirac-Fock计算

本文用相对论多组态Dirac-Fock广义平均模型(MCDF-EAL)计算了可能成为激光工作物质的类氮KXIII,CaXIV,ScXV和TiXVI的2s²p³,2s²p⁴,2p⁵,2s²p²3s,2s²p²3p组态的各44条精细结构和24条3s—3p组态跃迁波长,其中关于KXIII,CaXIV,ScXV的3s,3p组态的计算值是本文预言的。     

Lifetime measurements in Tm I,Tm II,and Tm III by time-resolved laser spectroscopy

Natural radiative lifetimes of eight levels in Tm I ( 4f ¹³5d6p and 4f ¹²5d6s ² configurations), two levels in Tm II ( 4f ¹²5d6s configuration) and three levels in Tm III (4f ¹²5d configuration) have been measured by using time-resolved laser spectroscopy. Free thulium atoms, as well as singly and doubly ionized ions, were obtained in a laser-induced thulium plasma and the investigated states were selectively populated by a single-step excitation process with a tunable narrow-band laser pulse. Received 20 August 2002 / Received in final form 7 January 2003 Published online 4 March 2003 RID="a" ID="a"e-mail: huailiang.xu@fysik.lth.se     

类氧钆离子辐射寿命的计算

本文使用多组态Dirac-Fock方法计算了类氧钆离子2s²2p⁴,2s2p⁵,2s²2p³s,2s²2p³3p组态的精细结构能级和激发态的辐射寿命,以及电偶极、磁偶极、电四极跃迁的波长、自发辐射几率、受激辐射几率和振子强度.计算结果可为可能的真空紫外激光器的研制提供必要的理论依据.     

Hyperfine structure and isotope shift studies of rhenium by laser optogalvanic spectroscopy

Doppler-limited high resolution laser optogalvanic spectra of six transitions of rhenium lying in the range 560–620 nm have been recorded. Isotope shifts between the two natural isotopes of rhenium,¹⁸⁵Re and¹⁸⁷Re, have been calculated in all the six transitions. Hyperfine coupling constants for eight levels belonging to the configurations 5d ⁵6s ², 5d ⁶6s, 5d ⁴6s ²6p and 5d ⁵6s6p are reported. Wherever possible our constants are compared with those given by others.     

Energy Levels, Transition Probabilities, Collision Strength, and Reduced Population Calculations for High Gain Predictions in Neon-Like Krypton

We calculate the atomic structure, energy levels, oscillator strengths, transition probabilities, and collision strengths for Kr XXVII. The data refer to the 157 fine-structure levels belonging to the configurations (1s²) 2s² 2p⁶, 2s²2p⁵3l, 2s¹2p⁶3l, 2s²2p⁵4l, 2s¹2p⁶4l, 2s²2p⁵5l, and 2s¹2p⁶5l, where l?=?s, p, d, f, and the calculations are performed using the fully relativistic atomic structure program FAC. We use the obtained data to calculate the level populations and gain coefficients employing the MATLAB R2012a computer program for solving simultaneously the coupled rate equations. Finally, we determine the 157 fine-structure population levels and gain coefficients for those transitions with a positive inversion factor and plot the electron density in wide range from 10¹⁹ to 10²³.     

Electron impact excitation collision strengths for neon-like Ni XIX calculated using the relativistic R-matrix method

In a recent paper [Pramana — J. Phys. 64, 129 (2005)] results have been presented for electron impact excitation collision strengths for transitions among the fine-structure levels of the 2s²2p⁶ and 2s²2p⁵3s configurations of Ni XIX. In this paper we demonstrate through an independent calculation with the relativistic R-matrix code that those results are unreliable and the conclusions drawn are invalid.     

Breit-Pauli energy levels and radiative lifetimes in neutral chlorine

Breit-Pauli Energy levels, oscillator strengths and transition probabilities for all the transitions in Cl I between the fine structure levels of 3s² 3p⁵, 3s² 3p⁴3d, 3s² 3p⁴4s and 3s²3p⁴4p states are calculated using extensive configuration interaction (CI) wave functions. We have also determined the lifetimes of 3s² 3p⁴3d, 3s² 3p⁴4s and 3s² 3p⁴4p levels. The relativistic effects are included through Breit-Pauli approximation via spin-orbit, Darwin and mass correction terms. Prior to the calculations of the oscillator strengths and transition probabilities, we fine-tune the CI coefficient using experimental energies. Our results are compared with experimental and other available theoretical data. The calculated energy levels are in close agreement with most of the NIST compiled data. We predict new lifetime data for several levels where no other theoretical and/or experimental results are available, which will form the basis for the future experimental work. Electronic supplementary material Online Material     

High gain predictions for Ni-like Gd ion

Atomic structure data and effective collision strengths for 1s² 2s² 2p⁶ 3s² 3p⁶3d¹⁰ and 54 fine-structure levels contained in the configurations 1s² 2s² 2p⁶ 3s² 3p⁶3d⁹4l (l = s, p, d, f) for the nickel-like Gd ion. These data are used in the determination of the reduced population for the 55 fine structure levels over a wide range of electron densities (from 10²¹ to 10²³) and at various electron plasma temperatures. The gain coefficient for those transitions with positive population inversion factor are determined and plotted against the electron density.     

Electron collisional excitation of argon-like Ni XI using the Breit-Pauli R-matrix method

Electron excitation collision strengths for the transitions from the ground state to the fine-structure levels of the 3s²3p⁵3d and 3s²3p⁶3d configurations in Ni XI are calculated using the Breit-Pauli R-matrix method. Configuration interaction wavefunctions have been used to represent the target states. The relativistic effects are incorporated in the Breit-Pauli approximation by including one-body mass correction, Darwin, and spin-orbit interaction terms in the scattering equations. Collision strengths are tabulated at selected energies in the range 10 to 75 Rydberg. Effective collision strengths are determined by integrating collision strengths by assuming a Maxwellian distribution of electron energies. The effective collision strengths are listed over a wide temperature range (2×10⁴-1×10⁷ K) applicable to astrophysical plasmas. Our results are the only collision strengths and effective collision strengths available for this ion. We believe that the data calculated in this work will be useful in solar, astrophysical and laser applications.     

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     

Lifetime of levels belonging to the 3p54p configuration of Ar(I)

The lifetimes of nine levels of Ar(I) belonging to the 3p⁵4p configuration have been measured by the delayed coincidence method, with errors in the range from 4 to 7%. The results are compared with other experimental values and with theoretical calculations using jK coupling and intermediate coupling. From cascade components of the 4p levels, decay lifetime values for some levels belonging to the 3p⁵3d and 3p⁵5s configurations have been inferred.     

C42+的几何构型和Jahn Teller效应

用从头计算法QCISD/6-311G得到了C₄²⁺分子的10种不同的几何构型,其中包括C_s,C_∞v,C_2v,D_2h,D_∞h,D_4h,D_2d,C_3v等不同的构型.计算表明C₄²⁺的T_d构型不能稳定存在,详细讨论了T_{d 关键词： 几何构型 4}²⁺')" href="#">C₄²⁺ Jahn Teller效应     

“Electron collisional excitation of argon-like Ni XI using the Breit-Pauli R-matrix method”

In a recent paper, Verma et al. [Eur. Phys. J. D 42, 235 (2007)] have reported results for energy levels, radiative rates, collision strengths, and effective collision strengths for transitions among the lowest 17 levels of the (1s²2s²2p⁶)3s²3p⁶, 3s²3p⁵3d and 3s3p⁶3d configurations of Ni xi. They adopted the civ3 and R-matrix codes for the generation of wavefunctions and the scattering process, respectively. In this paper, through two independent calculations performed with the fully relativistic darc (along with grasp) and fac codes, we demonstrate that their results are unreliable. New data are presented and their accuracy is assessed.     

Dielectronic recombination rate coefficients of Ni-like barium and tungsten

Ab initio calculations of the total dielectronic recombination (DR) rate coefficient of Ni-like barium () and tungsten () in the ground state have been performed using the HULLAC atomic code package. Resonant and nonresonant stabilizing radiative transitions are included. Collisional transitions following electron capture are neglected. The present level-by-level calculations include the DR contributions of all of the levels (over 17000) in the Cu-like inner-shell excited configurations 3d ⁹ 4ln'l' (), 3p ⁵ 3d ¹⁰ 4ln'l' (), and 3s3p ⁶ 3d ¹⁰ 4ln'l' (). For both ions, the configuration complexes with a hole in the 3p inner shell contribute almost 10% to the total DR rate coefficient, while the complexes with a hole in the 3s inner shell contribute about 1%. The converging contributions of the 3d ⁹ 4ln'l' (n' > 9) configurations are evaluated by applying the complex-by-complex extrapolation method and are found to comprise up to about 20% of the total DR rate coefficients throughout a wide electron temperature range. The total DR rate coefficients are fitted to an easy-to-use analytic expression which reproduces the original data with an accuracy of about 2% or better in a very wide temperature range. Received: 1 February 1999