Lifetimes of metastable states in Sr II

The lifetimes of the 4d ²D _3/2,5/2 levels of Sr⁺ have been determined both experimentally and theoretically. The experiment was performed at an ion storage ring utilising collinear laser excitation. The calculation was performed by the Hartree-Fock method including relativistic effects and core polarisation. The obtained lifetimes (which are about 0.4 s) are discussed in detail and compared with earlier published results. In addition, calculated lifetimes of a large number of excited states in Sr⁺ are included. Received 15 February 2000 and Received in final form 20 March 2000     

Spectra for electric-dipole Δn = 0 transitions in highly ionized sulfur ions

Spectra for Δn = 0 transitions of the type 2s²2p^k-2s2p^k+1 or 2s2p^k-2p^k+1 from highly ionized sulfur produced in beam-foil excitation are investigated and compared to similar spectra measured with other types of light sources. In the experiment, fifty lines have been identified, of which eleven lines are new and accurately measured. Analysis of spectra was based on comparisons with other experimental results and calculated values.     

Lifetime measurements for some levels in Be-like Cl XIV and S XIII

Lifetime measurements have been carried out for some low lying (n = 2) levels in the four-electron ions Cl XIV and S XIII using the beam-foil technique. Accurate oscillator strengths for the 2 s2 ¹ S - 2 s 2 p ¹ P o transition have been determined by the inclusion of prominent cascades in the analysis. Lifetimes of the levels of the 2 p2 ³ P j multiplet have also been measured for both ions. The results are compared with theoretical predictions and earlier measurements. Received: 29 October 1997 / Revised: 10 February 1998 / Accepted: 5 March 1998     

Radiative lifetimes of Zr III excited levels

We report on radiative lifetimes of 4d5p excited states of Zr III produced in a laser produced plasma. The ions were populated either in the ground state or in metastable states, and the number of ions is strongly dependent on the application of an external magnetic field, which is shown to be very important when using the time-resolved laser-induced fluorescence technique for lifetime measurements in highly charged ions. The experimental lifetime results fall in the region 1–2 ns with statistical uncertainties less than 7%. The experimental values were compared with multi-configuration Hartree-Fock calculations showing an agreement within 12–20%. The experimental values are systematically higher than the theoretical ones.     

Radiative lifetimes of 7d, 8d <Superscript>1</Superscript>D<Subscript>2</Subscript> excited states of Hg I

Radiative lifetimes of 7d, 8d ¹ D ₂ excited states of Hg I are measured using pulsed two-photon excitation from the ground [Xe]5d ¹⁰6s ^{2 1} S ₀ mercury state, detecting the decay of the laser-induced fluorescence. The results are compared with theoretical values, obtained by means of a Hartree-Fock single configuration method, taking into account electron configuration interaction. The radiative lifetime value dependence on the effective principal quantum number for the nd ¹ D ₂ series is analyzed and compared with the quantum defect dependence. Received 25 February 2000 and Received in final form 26 July 2000     

Radiative transitions in highly ionised silicon-like ions

Transition energies, oscillator strengths and transition probability values for radiative transitions have been calculated for the highly ionised atoms of Si isoelectronic sequence from Mn¹¹⁺ to Kr²²⁺ for the singly excited states up to principal quantum number n = 7. Time-dependent coupled Hartree-Fock (TDCHF) theory has been used to estimate such transition properties. Most of the results for the oscillator strengths and transition probabilities are new. Transition energies agree reasonably well with available spectroscopic values. Received 25 January 2000 and Received in final form 24 October 2000     

Lifetime measurements of some levels belonging to the 3p <Emphasis Type="Bold">5</Emphasis>nd ( , 5, 6, 7) configuration of ArI

Lifetimes of some 3p^5nd (n = 4, 5, 6, 7) levels of neutral argon have been measured by high frequency deflection technique with a delayed coincidence single photon counting arrangement. The measurements have been performed under conditions where pressure dependent effects are negligible. Lifetimes of some of the levels have been measured for the first time. The results have been compared with other experimental and theoretical values. Received 7 August 2002 / Received in final form 20 December 2002 Published online 24 April 2003     

Additional symmetry for the electronic shell in its ground state and many-electron effects

The additional symmetry for the properties related to the ground state of the atom is considered taking into account many-electron effects. Calculations of the I _4f, I _3d,I _2p,I _3p binding energies, 4f ^N-15d - 4f^N system differences and 2p, 3p electron affinities in the second order of perturbation theory and in the configuration interaction approximation have been performed for the ground configurations with one open shell. The analysis of separate many-electron corrections for these quantities and their variation along the sequences of atoms and ions shows that the main corrections maintain the considered symmetry. Received 18 January 1999 and Received in final form 17 July 1999     

Stark broadening of isolated lines: calculation of the diagonal multiplet factor for complex configurations (n1l1 n n2l2 m n3l3 p)

Owing to the increasing sensitivity of detectors, accurate line profiles are needed for accurate stellar atmospheres modelling and for laboratory and technological plasmas as well. So, Stark broadening parameters of isolated lines of complex atoms and ions within the impact and quasistatic approximation are needed, even if the atomic abundance of the considered element is low. Angular factors of the diagonal line strength entering the quadrupole term appearing in the semi-classical expression of the width of line broadened by electron or ion perturbers, are needed. The aim of this paper is to extend the previous calculations of this diagonal multiplet factor which were obtained for configurations of the type lⁿ and l₁ ⁿl₂ ^m to more complex configurations in LS coupling. To study the Stark broadening of isolated lines in the impact and quasistatic approximation, we use the semi-classical-perturbation treatment, including both dipole and quadrupole contribution in the expansion of the electrostatic interaction between the optical electron and the perturber. We also use the Fano-Racah algebra. Angular factors of the diagonal line strength entering the quadrupole term appearing in the semi-classical expression of the width of line broadened by electron or ion perturbers, are calculated. New diagonal multiplet factor formulae for more complicated configurations such as (n₁l₁ ⁿ(L_nS_n)n₂l₂ ^m(L_mS_m)n₃l₃ ^p(L_pS_p)) are provided. These formulae can enter the computer Stark semi-classical perturbation codes.     

Experimental and theoretical lifetimes in Yb III

Lifetimes of three levels belonging to the configuration 4f ¹³5d with J = 1 in Yb III have been measured for the first time using the time-resolved laser-induced fluorescence method. Experimental transition probabilities have been deduced for the transitions between the levels studied and the ground state. The comparison of the experimental lifetimes with theoretical data, deduced within the relativistic Hartree-Fock (HFR) approach, underlines the dramatic importance of an adequate consideration of core-polarization effects in the theoretical model and the sensitivity of one of the lifetime values to small correlation effects. Received 2 April 2001     

Radiative corrections to the magnetic-dipole transition amplitude in B-like ions

The one-electron quantum-electrodynamic corrections to the magnetic-dipole transition amplitude between the fine-structure levels (1s² 2s² 2p) ²P_3/2 - ²P_1/2 in boronlike ions are calculated to all orders in αZ. The results obtained serve for improving the theoretical accuracy of the lifetime of the (1s² 2s² 2p) ²P_3/2 level in boronlike argon.     

Experimental transition probabilities and improved level energies in Yb III

Radiative lifetimes of nine out of the twelve 4f¹³6p levels in Yb III have been measured, seven of these for the first time. A Penning discharge lamp is introduced as a continuous plasma source, in which the lifetimes are determined with the time-resolved laser-induced fluorescence technique by pumping from metastable 5d and 6s levels. Spectra of the same source are recorded with a Fourier-transform spectrometer, which are used to derive branching fractions of the 6p and 7s levels. Combined with the lifetimes, the branching fractions are used to determine 81 experimental transition probabilities. Wavelengths of 142 Yb III transitions are measured and the uncertainties of corresponding Ritz wavenumbers are improved by an order of magnitude from the prior values. The energy of the 5d (5/2,5/2)^○ ₀ level has been shifted 144.20 cm^-1 to the higher value 45421.045 cm^-1. Much emphasis is put on data treatment and error analysis. Electronic supplementary material Supplementary Online Material     

Line strength measurements for near-infrared intersystem transitions of NI

Intensities of 15 intersystem transitions and 5 LS allowed multiplets of neutral nitrogen (NI) from infrared part of the spectrum were measured by emission spectroscopy method. All allowed as well as LS-forbidden spectral lines belong to the 3p-3d transition array. The nitrogen spectra were excited in a wall-stabilized high-current arc ran in helium with small admixture of nitrogen. On the basis of these line (multiplet) intensity measurements, transition probabilities of 15 intersystem lines were determined relative to transition probabilities of appropriately chosen allowed multiplets. Finally the relative data for intersystem transitions were normalized to an absolute scale by applying reference multiplet strength values recommended by the Atomic Spectroscopy Group of NIST. The determined line strengths are compared with available calculated and — in the case of 5 transitions — also with experimental data.     

The and transitions in the oxygen isoelectronic sequence

Multiconfiguration Dirac-Fock results are reported for the and transitions in the oxygen-like sequence for Z =9,...,18. Both transition energies and transition rates are included. Received: 29 June 1998 / Accepted: 1st July 1998     

Experimental transition probabilities in N III,N IV and N V spectra

We have obtained transition probabilities (Einstein's A values) of thirteen transitions in doubly (N III), six in triply (N IV) and two in four times (N V) ionized nitrogen spectra belonging to the 3s-3p and 3p-3d transitions using a relative line intensity ratio (RLIR) technique. The linear low-pressure pulsed arc was used as an optically thin plasma source operated at 51 400 K electron temperature and 2.2×10²³ m^-3 electron density in nitrogen plasma. Our A values are compared to recent theoretical and experimental data. Received 18 December 2001 / Received in final form 29 January 2002 Published online 28 June 2002     

Transition wavelengths and probabilities for spectral lines of Zr III

Wavelengths and oscillator strengths for all 4d4f↦4d² dipole-allowed fine-structure transitions in Zr III have been calculated within the Multi-Configuration Dirac-Fock method with QED corrections. These transitions are included in the spectrum of some chemically peculiar stars, like the B-type star χ Lupi observed by the Hubble space telescope. The results are compared to existing experimental and semi-empirical data.     

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     

Theoretical overview of atomic parity violation

Recent advances in interpreting the most accurate-to-date measurement of atomic parity violation in Cs are reviewed. The inferred nuclear weak charge, Q _W( ^133Cs ) = - 72.65(28)_expt(36)_theor , agrees with the prediction of the standard model at 1σ level. Further improved interpretation is limited by an accuracy of solving the basic correlation problem of the atomic structure. We report on our progress in solving this problem within the relativistic coupled-cluster formalism. We include single, double and triple electronic excitations in the coupled-cluster expansion. Numerical results for energies, electric-dipole matrix elements, and hyperfine-structure constants of Cs are presented.     

Low energy emission bands in a small molecular fluorene derivative for organic light-emitting diodes

Quantum similarity is investigated for neutral atoms and singly charged ions by means of their one-particle densities in both position and momentum spaces. As recently observed for neutral atoms, the analysis involving singly charged ions in momentum space provides relevant information concerning structure and periodicity properties. Momentum-space similarity is also revealed to be strongly related to the kind of ionization process the system suffers, to the structural characteristics of the momentum density as well as to the ionization potential.     

Periodic orbits of the hydrogen molecular ion

Based on our previous work [Yiwu Duan, J.M. Yuan, C.G. Bao, Phys. Rev. A 52, 3497 (1995)], we study deeply the periodic orbits of the hydrogen molecular ion within the Born-Oppenheimer approximation (BOA). The Thiele-Burrau's transformation is introduced to regularize the singularities associated with the Coulomb potential terms and to transform the problem into a direct product of a pendulum and an anharmonic oscillator. This facilitates the analysis of the bifurcation properties of the periodic orbits. Some more details are also given about the calculation of the semiclassical density-of-state distribution using the Berry-Tabor formula. Received: 5 February 1999