Analysis of the 5p6p configuration of Xe V

The spectrum of four times ionized Xenon (XeV), has been observed in the 500–6800 Å range and 84 new lines have been identified as transitions between levels of 5s5p ³, 5s ²5p5d, 5s ²5p6s, 5s ²5p ², and 5s ²5p6p configurations. Nine new levels belonging to the configuration 5p6p have been determined. The results of this analysis are supported by Hartree-Fock calculations. The configurations are interpreted by fitting the theoretical energy parameters to the observed levels using least-squares techniques.     

Identification of new lines in the beam-foil spectrum of B II–IV

Ten, six, and twenty-one new lines appearing in the beam-foil spectra of boron (30–200 nm) have been identified in B II, B III, and B IV, respectively. Energies have been determined with higher accuracy than obtained before for the 2p3s ¹ P ⁰, 2s6d ³ D, 2p3p ³ D, 2p3p ³ S, 2p3p ³ P, and 2p3p ¹ D terms in B II. First energy values are also reported for the 2s6d ¹ D and 2s7d ³ D terms in B II.     

Identification of Δn≠0 quintet transitions in four-electronF 5+

Two Δn≠0 quintet transitions, 1s 2s 2p ^{2 5} P—1s 2s 2p 3d ⁵ P ⁰,⁵ D ⁰, have been identified in the beam-foil spectra of fluorine. The wavelengths are compared to theoretical predictions and to those of singly-excited five-electron ions.     

Beam-foil lifetime study of then=3 complex in al-like Ti9+

The beam-foil spectrum obtained using a beam of Ti³⁺ ions of energy 10 MeV has been studied over the wavelength range from 14 nm to 80 nm. New assignments are suggested for 18 levels belonging to the levels of the 3p ³, 3s 3p 3d and 3s ² 4p configurations. The lifetimes of these levels, as determined from conventional multi-exponential curve fitting of their intensity decay curves, are typically about 30% longer than is forecast by theory. The same decay curves have also been used to represent the effect of cascade repopulation on the decay curves obtained for the resonance doublet levels of the 3s 3p ² and 3s ² 3d configurations. A discussion is given of the possible techniques for cascade correction in beam-foil lifetime measurements, and of the inclusion of a window function to represent the vignetting effect close to the foil. Lifetimes obtained using these techniques for the 3s ² 3d levels (38±6 ps for J=3/2, 36±5 ps for J=5/2), and the 3s3p ^{2 2} S level (99±6 ps),² P levels (60±15 ps for J=1/2, 50±15 ps for J=3/2) and² D levels (820±30 ps for j=3/2, 870±40 ps for J=5/2) are in good agreement with theoretical predictions.     

3dnl J=3e autoionizing levels of calcium: observation by laser optogalvanic spectroscopy and theoretical analysis

The even parityJ=3 autoionizing spectra of calcium were investigated below the 3d threshold by a two-step laser excitation from the 3d4s metastables through the 3d4p ³ P ₂,¹ F ₃ intermediate states. The 3d4s were populated by electronic collisions in a d.c. glow dis-charge through a Ca heat-pipe. More than a hundred resonance transitions have been measured with an accuracy of ～0.2 cm^?1 for the narrow ones using standard laser calibration techniques. Their upper levels are assigned to all expected nine autoionizing 3dns, 3dnd and 3dng Rydberg series and the 4p 5p ³ D ₃ perturber. The theoretical interpretation is achieved by a combination of the eigenchannelR-matrix and mulitchannel quantum defect (MQDT) methods. Ten closed and two openJ=3 interacting channesl are used. Theoretical energy level positions and excitation profiles are compared with the experimental data confirming the identification of the observed structures. Strong mixing between the 3d _3/2 nd _5/2 and 3d _5/2 nd _3/2 series is found, while the 3d _3/2 nd _3/2 and 3d _5/2 nd _5/2 series are almost purejj-coupled. The calculations were particularly successful in reproducing the spectrum in the region of the 4p 5p ³ D ₃ perturber, where strong chancel mixing appears leading to interference effects in the excitation cross sections.     

Hyperfine structure in 5s 4d 3 D —5snf transitions of87Sr

The hyperfine spectra of the 5s4d ³ D ₁-5s20f, 5s4d ³ D ₂-5s23f, and 5s 4d ³ D ₃-5s32f transitions of⁸⁷Sr (I=9/2) have been measured by collinear fast beam laser spectroscopy. The structure in the upper configurations is highly perturbed by fine structure splitting that is of comparable size to the hyperfine interaction energy. These perturbations can be adequately treated with conventional matrix diagonalization methods, using the 5s-electron magnetic dipole interaction terma _5s and the unperturbed fine structure splittings as input parameters. Additionally, hyperfine constants for the lower 5s4d ³ D configurations, including theA- andB-factors and a separation of the individuals- andd-electron contributions to these factors, are derived.     

Theoretical study of LiK and LiK+ in adiabatic representation

The potential energy curves have been calculated for the electronic states of the molecule LiK within the range 3 to 300 a.u., of the internuclear distance R. Using an ab initio method, through a semiempirical spin-orbit pseudo-potential for the Li (1s ²) and K (1s ²2s ²2p ⁶3s ²3p ⁶) cores and core valence correlation correction added to the electrostatic Hamiltonian with Gaussian basis sets for both atoms. The core valence effects including core-polarization and core-valence correlation are taken into account by using an l-dependent core-polarization potential. The molecular orbitals have been derived from self-consistent field (SCF) calculation. The spectroscopic constants, dipole moments and vibrational levels of the lowest electronic states of the LiK molecule dissociating into K (4s, 4p, 5s, 3d, and 5p) + Li (2s, 2p, 3s, and 3p) in ^{1, 3}Σ, ^{1, 3}Π, and ^{1, 3}Δ symmetries. Adiabatic results are also reported for ²Σ, ²Π, and ²Δ electronic states of the molecular ion LiK⁺ dissociating into Li (2s, 2p, 3s, and 3p) + K⁺ and Li⁺ + K (4s, 4p, 5s, 3d, and 5p). The comparison of the present results with those available in the literature shows a very good agreement in spectroscopic constants of some lowest states of the LiK and LiK⁺ molecules, especially with the available theoretical works. The existence of numerous avoided crossing between electronic states of ²Σ and ²Π symmetries is related to the charge transfer process between the two ionic systems Li⁺K and LiK⁺.     

1/Z perturbation theory for calculation of line strengths in the neon isoelectronic sequence

The line strengths of 2–2 and 3–3 transitions (2s²2p⁵3s–2s²2p⁵3p–2s²2p⁵3d, 2s2s2p⁶3s–2s2p⁶3p-2s2p⁶3d, 2s²2p⁵3l-2s2p⁶3l) have been calculated for the Ne isoelectronic sequence (Z = 14 ÷ 100). The calculation has been carried out in intermediate coupling. Relativistic corrections have been included through the Breit operator. Perturbation theory in 1/Z has been used to account for electronic interactions.     

Laser spectroscopic investigation of isotope shifts in Nd II lines

The isotope shift of 11 optical transitions in Nd II in the spectral range 420–450 nm have been recorded (in all cases but one for all pairs of even Nd isotopes). For all observed transitions the values of the field shifts, the specific mass shifts and Δ∣ψ(0)∣² have been evaluated. Using our new data, combined with data reported in earlier papers, term isotope shifts for all pairs of even Nd isotopes have been determined for 27 energy levels and for the configurations: 4f⁴6s, 4f⁴5d, 4f³5d6s and 4f⁴6p as well. It is shown that configuration assignment of a level on the basis of term shift values only is in some cases not satisfactory (as e.g. of the level at 22,696 cm⁻¹) and obviously additional information is required.     

Hyperfine structure measurements in tantalum I using laser saturation spectroscopy in a sputtered vapour

Magnetic hyperfine interaction constants (A factors) and electric quadrupole interaction constants (B factors) have been determined for sixteen levels in tantalum I using the method of saturated absorption spectroscopy in a sputtered vapour. Five of these levels belong to the lowest configuration 5d ³ 6s ² which has been studied previously by other workers, and for one of these levels, thea ⁴ P _5/2 at 9253 cm^?1, our results are new. For the eleven levels belonging to the excited configurations 5d ³ 6s 6p and 5d ² 6s ² 6p our values are the first data reported in the literature.     

Hyperfine structure and isotope shift of some even parity levels in the YbI spectrum

Using laser induced fluorescence spectroscopy the hyperfine structure of the even parity levels 4f ¹⁴6s6d ³ D ₁, 4f ¹⁴ 6s8s ³ S ₁ and 4f ¹³ 5d6s6p (7/2, 5/2)J=1,2,3 as well as of the odd parity level 4f ¹⁴ 6s6p ³ P ₂ in neutral ytterbium has been investigated. The isotope shift of the transitions 4f ¹⁴6s6p ³ P ₀ → 4f ¹⁴ 6s6p ³ D ₁ and 4f ¹⁴ 6s6p ³ P ₂ → 4f ¹⁴ 6s8s ³ S ₁, 4f ¹³ 5d6s6p (7/2, 5/2)J=1,2,3 could be measured with high accuracy. The results for the 4f ¹⁴ 6s6p ³ D ₁ level show a considerable influence of second order effects of the hyperfine interaction. The isotope shifts of the 4f ¹⁴ 6s8s ³ S ₁ and 4f ¹³ 5d6s6p (7/2, 5/2)J=1 levels indicate a possible configuration mixing for these levels.     

Two-step laser optogalvanic spectroscopy of highJ momentum 4dnd and 4dng autoionizing states of strontium

We have measured the energies of about two hundred even parityJ=3–5 autoionizing 4dnd and 4dng Rydberg states of strontium (Sr) using an optogalvanic method. These states are reached by a two-step dye laser excitation from the 4d5s metastables through the 4d5p ³ P ₂,¹ F ₃,³ F ₄ intermediates. The 4d5s are populated in a d.c. glow discharge through a Sr heated cell. The electronic configuration of the observedJ=3, 4 states is deduced from the Lu-Fano plots of their quantum defect values and the spectral characteristics of the corresponding transitions.     

Precision energies and hyperfine structures of the 5s5p 3 P 0,1,2 0 and 5s6s 3 S 1 levels in In II

Absolute frequencies of hyperfine components of the 230.6 nm (5s ^{2 1} S ₀?5s5p ³ P ₁ ⁰ ), 193.6 nm (5s5p ³ P ₀ ⁰ ?5s6s ³ S ₁), 197.7 nm (5s5p ³ P ₁ ⁰ ?5s6s ³ S ₁) and 207.9 nm (5s5p ³ P ₂ ⁰ ?5s6s ³ S ₁) transitions in In II emitted from a hollow-cathode source have been measured using a high-resolution, scanning échelle monochromator. The measured frequencies of these four transitions have been used to determine the energies and hyperfine interaction constants of the 5s5p ³ P ₀ ⁰ ,³ P ₁ ⁰ ,³ P ₂ ⁰ and 5s6s ³ S ₁ levels in In II. The hyperfine interaction constants for the dominant isotope¹¹⁵In are found to be: 5s5p ³ P ₁ ⁰ A=0.2322(2) cm^?1,B=?0.0159(9) cm^?1 5s5p ³ P ₂ ⁰ A=0.1699(4) cm^?1,B= 0.021 (6) cm^?1 5s6s ³ S ₁ A=0.4022(4) cm^?1,B= 0.002 (2) cm^?1. The absolute frequency of the very narrow, strongly forbidden In II 236.5 nm (5s ^{2 1} S ₀?5s5p ³ P ₀ ⁰ ) transition, which has been proposed as a candidate for a new optical frequency standard, is found to be 42275.986(7) cm^?1.     

Wavelength and isotopic shift measurements of the3S(3s 4s) −3P(3s 3p) MgI transitions

The wavelengths of the³S(3s 4s) ?³P(3s 3p) MgI transitions have been measured for the²⁴Mg isotope with a precision of ±2 × 10^?7; moreover the isotope shifts of the above transitions have been measured for the three natural Mg isotopes as well as the hyperfine constants of the³S(3s 4s) level of²⁵Mg. The measurements have been performed in a metastable atomic beam.     

On the line intensity ratios of prominent Si II,Si III,and Si IV multiplets

Line intensities of singly, doubly and triply ionized silicon (Si II, Si III, and Si IV, respectively) belonging to the prominent higher multiplets, are of interest in laboratory and astrophysical plasma diagnostics. We measured these line intensities in the emission spectra of pulsed helium discharge. The Si II line intensity ratios in the 3s3p²²D–3s²4p²P^o, 3s²3d²D–3s²4f²F^o, and 3s²4p²P^o–3s²4d²D transitions, the Si III line intensity ratios in the 3s3d³D–3s4p³P^o, 3s4p³P^o–3s4d³D, 3s4p³P^o–3s5s³S, 3s4s³S–3s4p³P^o, and 3s4f³F^o–3s5g³G transitions, and the Si IV line intensity ratios in the 4p²P^o–4d²D and 4p²P^o–5s²S transitions were obtained in a helium plasma at an electron temperature of about 17,000 ± 2000 K. Line shapes were recorded using a spectrograph and an ICCD camera as a highly-sensitive detection system. The silicon atoms were evaporated from a Pyrex discharge tube designed for the purpose. They represent impurities in the optically thin helium plasma at the silicon ionic wavelengths investigated. The line intensity ratios obtained were compared with those available in the literature, and with values calculated on the basis of available transition probabilities. The experimental data corresponded well with line intensity ratios calculated using the transition probabilities obtained from a Multi Configuration Hartree–Fock approximation for Si III and Si IV spectra. We recommend corrections of some Si II transition probabilities.     

Energies of Sr states with excited valence shell

Singly- and doubly-excited Sr states emerging upon excitation of the valence shell have been investigated. Only states with low values of the principal quantum numbern of the valence electrons have been considered: 5s4d, 5s5p, 5p ², 4d ² and 4d5p. These states have been treated by a perturbation theory based on the Dirac equations with model potential, the valence electrons interaction being considered as a perturbation. The zero-order approximation accounts for the main contributing interactions including the strong core potential screening. The applied calculation method was previously developed for highly-excited Rydberg states but its application also for states with lown was proved to be suitable.     

Optical isotope shifts in titanium I: new measurements

The optical isotope shifts between ⁴⁶Ti, ⁴⁸Ti and ⁵⁰Ti have been measured for eight 3d ³ 4s a ⁵F-3d ² 4s 4p y ³ F lines of titanium by use of a Doppler-free experiment. By contrast with the positive shifts previously measured for 3d ² 4s ² a ³ F-3d ² 4s 4p z ⁵ D lines, these shifts are negative and reveal the presence of large negative specific mass shifts attributed to a d-p electron jump. The interpretation of the present measurements and of former ones is made by means of Hartree-Fock calculations.     

Beam-foil lifetime data for 3s 3p 3 and 3s 2 3p 3d levels of Si-like Ni14+

In the EUV spectrum of foil-excited 24 MeV Ni ions the decays of the 3s 3p ³ and 3s ² 3p 3d levels to the 3s ² 3p ² levels of the ground configuration have been observed. For most of the levels decay curves have been obtained. The lifetime results compare well with predictions from semi-empirically scaled HXR calculations. Some problems with cascade repopulations will be discussed.     

Intercombination lines of Mg I-, Al I- and Si I-like ions in the beam foil spectra of Ti,Fe, Ni and Cu

In delayed spectra of foil-excited beams of Ti, Fe, Ni and Cu ions lines have been observed which are identified with intercombination transitions 3s ^{2 1} S ₀ — 3s 3p ³ P ₁ ⁰ , 3s ² 3p ² P ⁰ — 3s 3p ^{2 4} P and 3s ² 3p ^{2 3} P — 3s 3p ^{3 5} S ₂ ⁰ in magnesiumlike, aluminiumlike and siliconlike spectra, resp. Wavelengths and decay properties have been determined. The results are compared to recent theoretical predictions.     

Hyperfinestructure-investigations in the mangan I configurations 3d 5 4s 4p and 4s 5s

Nine transitions (ranging from 475 till 733 nm) between the excited configuration 3d ⁵ 4s 5s and 3d ⁵ 4s 4p of⁵⁵Mn were investigated with computer supported interference spectroscopy. Thus the hyperfine structure (hfs) of the four 4s 5s and the twelve 4s 4p levels is now completely known from experiment. The hfs results are discussed with the effective operator technique and for 4s 4p the accuracy of the one-electron parametersa ^ik could be improved:a _3d ¹⁰ =?6.28(24),a _4s ¹⁰ =154.0(1.4),a _4p ⁰¹ =9.3(8),a _4p ¹² =7.7(2.5) in mK. For the configuration 4s 5s — for which fine structure calculations are not yet available — the experimental hfs data prove a practically pureS-character. Besides the one-electron splitting parameters deduced:a _3d ¹⁰ =?6.5(5),a _4s ¹⁰ =182(3),a _5s ¹⁰ =24(3) in mK, permit to determine the degree of mixing between the twoe ⁶ S _5/2 andf ⁶ S _5/2 levels which amounts to about 3%.