Study of the energy level structure for the isoelectronic series of scandium-like ions

The structure of the energy level system for 39 ions of the scandium isoelectronic sequence is studied on the basis of the relativistic self-consistent field method taking into account the configuration interaction. The Dirac-Fock equations are solved with subsequent diagonalization of the energy matrix. The ground-state ionization potentials are determined for each ion. The energy levels corresponding to the 3d4s ², 3d ²4s, and 3d ₃ configurations are also calculated. The obtained energy values are compared with the experimental data as well as with the results of calculations carried out by other authors.     

Multiconfiguration Hartree-Fock calculations in Cr5+, Mn6+ and Fe7+

The multiconfiguration Hartree-Fock (MCHF) method is used to calculate the excitation energies and oscillator strengths, of both the length (f _L) and velocity (f _V) forms, for 1s²2s²2p⁶3s²3p⁶3d² D→1s²2s²2p⁶3s²3p⁵3d^{2 2} P ⁰,² D ⁰,² F ⁰ transitions in Cr⁵⁺, Mn⁶⁺ and Fe⁷⁺ ions of the potassium isoelectronic sequence. Comparison is made with our earlier relevant results obtained by employing the configuration interaction (CI) method which is closely related to the MCHF method. Our present investigation demonstrates that the MCHF method is more accurate than the CI method in all ions of present consideration.     

Hyperfine-structure and isotope-shift measurements in the 6s 5d↔6p 5d transitions of Ba I in the far-red spectral region

Measurements of the hyperfine structures in the 6p5d ¹ D ₂,³ D ₁ and³ F _{2, 3, 4} states of¹³⁵Ba and¹³⁷Ba, and isotope-shifts in several far-red transitions between the 6s 5d and 6p 5d configurations, as well as the transition 6s ^{2 1} S ₀→6s6p ³ P ₁ at 7,911 Å have been performed using high-resolution laser spectroscopy on a collimated atomic beam of natural barium. An analysis of the magnetic-dipole interaction in the 6p 5d configuration using effective one- and two-body hyperfine operators is presented. In particular the contact interaction was studied with respect to the correlation between the two valence electrons. Effects of strong configuration interaction were found. From a King-plot analysis of the isotope shift term- andJ-dependence of the field shift have been evaluated for the transitions between the 6s 5d and 6p 5d configurations. Relativistic Hartree-Fock (RHF) calculations have been performed of electron densities at the nucleus for six different configurations in Ba I and Ba II. The RHF calculations reproduce the experimental King-plot slopes quite well, while the absolute values, of the changes in electron density at the nucleus for the studied transitions, are found to be 9% lower than the results derived from a muonic experiment.     

Low pressure broadening and shift of the 2p 53p-2p 56s neon spectral lines

Natural radiative lifetimes in the perturbed 6s n s ¹ D ₂ (n=12?30) sequence of barium have been measured using the PUMOLS (PUlse-MOdulated Laser Spectroscopy) method, which incorporates pulse-modulation of a CW dye-laser beam and delayed coincidence techniques. Principal perturbers are the 5d 7d ³ F ₂ and¹ D ₂ states. Lifetimes were also measured for these shortlived valence states, which through configuration mixing cause drastic decreases in lifetime values in the region of perturbation of the 6s n d ¹ D ₂ sequence. Two-step laser excitation from the ground 6s ^{2 1} S ₀ state via the 6s 6p ¹ P ₁ state was employed. Special care was taken to determine the influence of black-body radiation transitions on the measured lifetimes.     

Fine- and hyperfine structure analysis of the odd configurations in the lead atom

The fine- and hyperfine structure (hfs) analysis, on the basis of available experimental data for the configuration 6s ²6p6d+6s ²6p7s+6s ²6p8s in PbI has been performed. The Slater integrals, spin-orbit parameters and the effective hfs one-electron parameters have been determined. We find an off-diagonal core-polarization effect in the 6p6d+6p7s-space. Using the calculated radial parameters, the values of the quadrupole moment for stable and radioactive Pb-nuclei have been determined from measuredB-factors of the 6p7s ³P₁ state. In addition, a repulsion effect on the hfs sublevels with the same quantum numberF has been investigated.     

Theoretical study of photoionization of the isoelectronic sequence Rb<Superscript>+</Superscript>, Sr<Superscript>2+</Superscript>, and Y<Superscript>3+</Superscript>

The photoionization cross sections for the 4p shell of ions of the Kr isoelectronic sequence Rb⁺, Sr²⁺, and Y³⁺ are calculated. The configuration interaction theory and the perturbation theory are used to describe the many-electron effects. The relativistic effects are taken into account in the Pauli-Fock approximation. The calculated resonance structure of photoionization cross sections for the 4p shell in the region below the 4s threshold associated with the autoionization of the 4s-np singly excited states and the 4p4p-nln′l′ doubly excited states reproduces the results of recent measurements of total photoabsorption cross sections for the Rb⁺, Sr²⁺, and Y³⁺ ions. It is found that, as the nuclear charge in the isoelectronic sequence increases, the ratio between the direct and correlation parts of amplitudes of the 4s-(n/?)p transition changes and, as the consequence, the minimum of the photoionization cross section of the 4s shell shifts from the continuous spectrum to the region of states of discrete spectrum. This accounts for the strong changes in the shape of the 4s-np resonances in the photoionization cross sections for the 4p shell of Rb⁺, Sr²⁺, and Y³⁺, as well as the distinction between the shapes of the 4s-6p _1/2 mirror resonance in the partial 4p _1/2 and 4p _3/2 photoionization cross sections for the Y³⁺ ion which do not suppress each other in the total photoionization cross section, as is the case for similar resonances in Rb⁺ and Sr²⁺.     

4d 95p 2 configuration in the spectra of in III-Te VI

The radiative 4d ¹⁰5p-4d ⁹5p ² transitions in the spectra of the In III, Sn IV, Sb V and Te VI, ions, belonging to the silver isoelectronic sequence, have been investigated in the range 250–600 Å with high resolution. The energies of most levels of the 4d ⁹5p ² configuration with J = 1/2, 3/2, and 5/2, involved in the transitions to the 4d ¹⁰5p configuration, are found. Along the isoelectronic sequence, the 4d ⁹5p ² configuration passes from the position below the ionization limit 4d ¹⁰ in Te VI to the position above this limit in In III with corresponding autoionization effects. The autoionization widths of levels are measured. The data obtained are compared with the results of calculations by the Hartree-Fock and semiempirical methods.     

Proton collisional excitation among the 2p53s configuration levels in the Ne isoelectronic sequence ions Na II-Ni XIX

Proton collisional excitation cross-sections and rate constants are presented for transitions among the 2p⁵3s configuration levels in the Ne isoelectronic sequence ions Na II-Ni XIX. The calculations are made according to symmetrized semiclassical impact parameter theory in which the truncated Schrödinger equation for quadrupole excitation is integrated directly. Various single configuration Hartree-Fock results are also given. The density and temperature regimes for which this process can have useful plasma diagnostic applications for these ions is discussed.     

Tensor polarizabilities of levels of the configurations 4f 13 6s6p and 4f 12 5d6s 2 in thulium I

The level-crossing technique with parallel electric and magnetic fields was used to measure the tensor polarizabilities of six levels of the configuration 4f ¹³ 6s6p + 4f ¹² 5d6s ² in the Tm I-spectrum. Using intermediate coupling wave functions given by Camus and the experimental values of the tensor polarizabilities, the radial integrals for electric dipole transitions from levels of the configuration 4f ¹³6s6p + 4f ¹²5d6s ² to levels of the configuration 4f ¹³ 5d6s + 4f ¹² 6s ²6p have been determined. The results areI(4f ¹³6s6p,4f ¹³5d6s)=1.98(45)ea ₀ andI(4f ¹²5d6s ²,4f ¹²6s ²6p) = 0.88(25)ea ₀. A comparison between the experimental and the calculated values of the tensor polarizabilities shows an excellent agreement, provided that these radial integrals and the radial integrals for the electric dipole transitions to the ground state configuration 4f ¹³6s ² as determined by Wallenstein from lifetime measurements are used in the calculation, instead of radial integrals computed by Camus with Hartree-Fock wave functions.     

类镍等电子系列离子M1,M2,E2禁戒跃迁特性的理论研究

利用基于全相对论框架下的多组态Dirac-Fock理论方法发展起来的程序包GRASP92和新发展的处理辐射跃迁过程的程序REOS99，计算了类镍等电子系列离子(Z=45—95)的基组态3s²3p⁶3d¹⁰¹S₀以及低激发组态3s²3p⁶3d⁹4l,3s²3p⁵3d¹⁰4l和3s3p⁶3d¹⁰4l(l=s,p,d,f)的能级及其向基态的M1,M2,E2禁戒跃迁概率.通过分析高离化类镍离子在特定的原子序数范围内由于存在能级交叉而产生的强组态相互作用，解释了高离化类镍离子禁戒跃迁概率的反常变化现象，探讨了禁戒跃迁概率受强组态相互作用影响而变化的一般规律.     

Laser photoelectron spectrometry of Sc− and Y−: A determination of the order of electron filling in transition-metal anions

The photoelectron spectra of Sc^? and Y^? have been obtained in a crossed ion- and laser-beam experiment. Analysis of the Sc^? spectrum yields two bound terms of 3d4s² 4p configuration (¹D⁰ and ³D⁰), with EA(Sc) = 0.189 ± 0.020 eV and an excited-state binding energy of 0.042 ± 0.020 eV. Similarly, the (4d5s² 5p) ¹D⁰ ground state of Y^?is bound by 0.308±0.012eV and a (4d5s²5P)³D⁰ excited term is bound by 0.165± 0.025 eV. With the determination of the bound electronic configuration of Sc^? as 3d4s²4p, the order of filling of electron shells of the first transition series negative ions is found to be 4s²4p, 3d4s²4p, followed by 3d^k4s² (k = 3,4,…, 10).     

Investigation of hyperfine structure and isotope shift of the 605.5 nm-line of Lu176 by laser spectroscopy

Using a tunable single mode dye laser the hyperfine structure of the transition 5d6s ^{2 2} D _5/2 — 5d6s6p ⁴ F _5/2 has been investigated for the Lu-isotopes Lu¹⁷⁵ and Lu¹⁷⁶. From our measurements the following values for the hyperfine constantsA andB could be deduced Lu¹⁷⁶ 5d6s6p ⁴ F _5/2:A=698.4 (0.4) MHz,B=1,564 (10) MHz 5d6s ^{2 2} D _5/2:A=104.1 (0.3) MHz.B=2,631 (6) MHz Lu¹⁷⁵ 5d6s6p ⁴ F ^5/2:A=987.2(0.4) MHz,B=1,117(6) MHz. The isotope shift between the line centers has been determined to be IS(176-175, 605.5 nm)=?420(10) MHz.     

Energy levels of ions of silver and rhodium isoelectronic sequences with <Emphasis Type="Italic">Z</Emphasis> < 86

The method of extrapolation of the parameter of a model potential for states of one electron (4f, 5s, 5p, 5d, 5f) above the core 1s ²2s ²2p ⁶3s ²3p ⁶3d ¹⁰4s ²4p ⁶4d ¹⁰ and one vacancy (4d ⁹) in the same core is applied to calculate the energy levels in the silver and rhodium isoelectronic sequences with the maximum nuclear charge Z = 86. The energy levels of Ag-and Rh-like ions were used for the calculation of the energies of resonance transitions to the ground state ¹ S ₀ in Pd-like ions. Good agreement between the theoretical and calculated energies of the resonance transitions in Pd-like ions indicates the reliability of the results obtained.     

Radiative constants in the spectra of ions of the krypton isoelectronic sequence

The probabilities of the 4p ⁶,4p ⁵5p→4p ⁵(4d+5s) radiative transitions and the radiative lifetimes of the 4p ⁵4d,4p ⁵5s, and 4p ⁵5p levels are calculated semiempirically for the RbII-MoVII isoelectronic sequence.     

Fine-Structure Splittings of Nitrogen Isoelectronic Sequence： Competitions among Spin-Orbit Interactions, Breit Interactions and Electron Correlations

Using the multi-configuration Dirac-Fock self-consistent field method and the relativistic configuration interaction method with quantum-electrodynamics corrections performed by the GRASP code, we calculate the fine-structure energy levels of the ground-state configuration （1s^22s^22p^3） of the nitrogen isoelectronic sequence, according to the L-S coupling scheme with atomic number Z up to 22. Based on the calculated results, we elucidate the mechanism of the orderings of fine-structure energy levels of 2^ D3/2,5/2 and 2^P1/2,3/2 respectively, i.e. for 2^D3/2,5/2 orderings, the competition between the spin-orbit interactions and the Breit interactions; for 2^P1/2,3/2 orderings, the electron correlations, especially the electron correlations owing to the 2p^5 configuration interactions.     

Spectroscopic investigations and configuration-interaction-assisted crystal field analysis of Pr in YPO4 single crystal

An optical study of a Y_0.99Pr_0.01PO₄ single crystal is presented. Measurements of optical absorption, excitation, and emission by selective excitation into ¹D₂, ³P₀ and ³P₁, at different temperatures between 20 and 295 K, are described. A detailed account of the line assignments is given for absorption in the 4300-23 000 cm⁻¹ spectral range, and for emission in the 6400-23 000 cm⁻¹ range. The lifetimes of the emitting levels are determined. Vibronic sidebands accompanying absorption, emission and excitation spectra are reported. The decay processes of the ³P₁, ³P₀ and ¹D₂ levels are discussed. The aim of this study is a test of the configuration-interaction-assisted crystal field analysis as well as the accurate experimental determination of the energy level scheme. It was reported previously that the introduction of configuration interaction between the ground 4f² configuration with the excited 4f6p configuration always resulted in a decrease (≈50-60%) in the standard deviations between the observed and calculated energy levels. In the present work the 4f5d configuration is included as well. The crystal field is analysed in the theoretical D_2d site symmetry with and without configuration interaction. The results with 4f², 4f²+4f5d, 4f²+4f6p and 4f²+4f5d+4f6p are given. The calculation on the basis of the 315 (4f²+4f5d+4f6p) levels gives the best overall standard deviation lowering it by 75% with regard to the calculation on the 91 4f² levels only.     

Analysis of the spectrum of the Zn-like Kr VII ion: Highly excited 4<Emphasis Type="Italic">p</Emphasis>4<Emphasis Type="Italic">d</Emphasis> and 4<Emphasis Type="Italic">p</Emphasis>5<Emphasis Type="Italic">s</Emphasis> configurations

The spectrum of the Zn-like Kr VII ion, excited in a capillary discharge and recorded with a high resolution in the wavelength range of 300–1000 Å, was studied. Previously performed identification of the transitions from the levels of the 4s4f, 4s5s, 4s5p, and 4s5d configurations is confirmed and extended, and the energies of these levels are specified. The (4p ²+4s4d)?4p4d and (4p ²+4s5s)?4p5s transitions are identified for the first time, and the energies of all the levels of the 4p4d and 4p5s configurations are determined. The results of the analysis performed are confirmed by semiempirical calculations in terms of the Hartree-Fock method. These results are also shown to conform to the experimental data obtained for lighter ions of the Zn I isoelectronic sequence.     

Laser spectroscopy of stable Os isotopes

Doppler-free isotope shift measurements of the stable even ^184–192Os and ^187,189Os odd isotopes have been performed for the first time on the 5d ⁶6s ^{2 5}D₄→5d ⁶6s6p ⁷F₄ (305.9 nm) transition in the neutral atom by atomic beam laser spectroscopy and on the ionic 5d ⁶6s ⁵D_9/2→5d ⁶6p ⁶D_7/2 (228.2 nm) transition by fast collinear ion-laser spectroscopy. The measurements were carried out in Manchester and at the IGISOL facility in Jyväskylä in Finland, respectively. The results presented are the most precise measurements to-date of the absolute isotope shifts.     

Stark-Effekt-Untersuchungen der Hyperfeinstruktur der 5s25d2D3/2- und 5s25d2D3/2-Terme im In I-Spektrum

The level-crossing technique with combined electric and magnetic fields was used to investigate the hyperfine structure of the 5s ²5d ² D _3/2- and 5s ²6d ² D _3/2-stedes of the In I-spectrum. From the shifts of the level-crossing signals due to the Stark effect of the electric field the Stark constantsβ of both states were deduced: 5s ²5d ² D _3/2: ¦β¦=0.33(3) Mc/(kV/cm)² 5s ²6d ² D _3/2: ¦β¦=6(1) Mc/(kV/cm)². By theoretical calculations with wave functions of the Coulomb approximation one can show, that the Stark effect in both states is mainly due to admixtures of the 5s ²6p- resp.5s ²7p-configuration.     

Analysis of the spectra of In XII–XIV and Sn XIII–XV in the far-VUV region

The 4p ⁶4d?(4p ⁶5p + 4p ⁶4f + 4p ⁵4d ²) transitions in the spectra of In XIII-Sn XIV and the 4p ⁶4d ²?(4p ⁶4d5p + 4p ⁶4d4f + 4p ⁵4d ³) transitions in the spectra of In XII-Sn XIII are investigated. About 150 spectral lines in the wavelength range 120–160 Å, which is important for projection vacuum UV lithography, have been classified for the first time. The fine structure intervals of the ground state 4p ⁶4d ² D and the energies of eight levels of the 4p ⁶5p, 4p ⁶4f, and 4p ⁵4d ² configurations are measured in each spectrum of In XIII and Sn XIV. The energies of all levels of the ground configuration 4p ⁶4d ² and the energies of 35 levels of the interacting configurations (4p ⁶5p + 4p ⁶4f + 4p ⁵4d ³) are determined in the spectra of In XII and Sn XIII. The resonant transitions 4p ^{6 1} S ₀?4p ⁵4d ¹ P ₁ in the spectra of In XIV and Sn XV are also identified. The semiempirical parameters of the configurations under study determined by mean-square fitting of measured level energies are in agreement along both isoelectronic and isonuclear sequences of the spectra.