Lifetime measurements and calculations in La I

Radiative lifetime measurements have been performed, with a time-resolved laser-induced fluorescence technique, for 20 odd-parity levels of La I belonging to the configurations 5d ²6p, 5d6s6p and 4f5d6s. The new results are compared with the few experimental data available in the literature and with theoretical calculations including configuration interaction effects. The agreement theory-experiment is generally satisfying but discrepancies are observed for some levels emphasizing the difficulty to get a reliable theoretical model in such a heavy and complex neutral element.Received: 26 January 2004, Published online: 22 June 2004PACS: 32.70.Cs Oscillator strengths, lifetimes, transition moments - 42.62.Fi Laser spectroscopy     

Optische Untersuchung der Hyperfeinstruktur einiger La I-Linien und Interpretation der gemessenenA-Faktoren

Several La I transitions were investigated by means of optical interference spectroscopy. AllA-values of the levels of the configuration 5d 6s 6p withJ=9/2, 7/2, and 5/2 were measured. Applying sum rules, the one-electrona-valuea _6s (5d 6s 6p) was derived. It is shown that a promising interpretation of the measuredA-values cannot be done without properly considering core-polarization and configuration interaction with adjacent configurations.     

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     

Fine-structure energy levels, oscillator strengths and lifetimes in Co XV

Excitation energies from ground state for 97 fine-structure levels as well as oscillator strengths and radiative decay rates for all electric-dipole-allowed and intercombination transitions among the fine-structure levels of the terms belonging to the (1s ²2s ²2p ⁶)3s ²3p, 3s ³ p ², 3s ²3d, 3p ³, 3s3p3d, 3p ²3d, 3s3d ², 3s ²4s, 3s ²4p, 3s ²4d, 3s ²4f, and 3s3p4s configurations of Co XV 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. Our calculated excitation energies, including their ordering, are in excellent agreement with the experimental results and the experimentally compiled energy values of the National Institute for Standards and Technology (NIST) wherever available. The mixing among several fine-structure levels is found to be very strong, with most of the strongly mixed levels belonging to the (1s ²2s ²2p ⁶)3p ²3d and 3s3d ² configurations. The strong mixing among several fine-structure levels makes it very difficult to identify them uniquely. Perhaps, that may be the reason for the lack of both experimental and theoretical results for these levels. We believe that our extensive calculated values can guide experimentalists in identifying the fine-structure levels in their future work. From our radiative decay rates we have also calculated radiative lifetimes of some fine-structure levels. In this calculation we also predict new data for several fine-structure levels where no other theoretical and/or experimental results are available.     

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

The probabilities of the 4f ¹³6p→4f ¹³5d lectric dipole transitions and the lifetimes of levels of the 4f ¹³6p and 4f ¹³5d configurations are calculated for spectra of ions Yb III, Lu IV, Hf V, and Ta VI of the erbium isoelectronic sequence. The wave functions of the intermediate coupling scheme, necessary for calculating the relative line strengths, are obtained semiempirically from experimentally measured energy intervals between fine-structure levels. To pass to the absolute values, the radial integrals of transitions, evaluated with the Hartree-Fock functions, are used.     

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.     

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 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.     

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.     

The probabilities of radiative transitions and lifetimes of levels in the spectra of Cu XX,La IV

The probabilities of radiative electric dipole transitions 2p ⁵3p, 2p ⁶–2p ⁵3s, and 2p ⁵3d in the spectrum of neon-like copper Cu XX and 5p ⁵6p, 5p ⁶–5p ⁵6s, 5p ⁵7s, and 5p ⁵5d in the spectrum of xenon-like lanthanum La IV are calculated. The wave functions of the intermediate coupling were found from the wellknown experimental energy levels by the least-squares method (LSM). To transfer to an absolute scale the radial integrals for the transitions calculated in the form of a length on the Hartree–Fock functions have been used. By summing the calculated probabilities of the transitions, the lifetimes of the levels of configurations 2p ⁵3s, 2p ⁵3p, and 2p ⁵3d in the spectrum of Cu XX and levels of configurations 5p ⁵6s, 5p ⁵6p, and 5p ⁵7s in the spectrum of La IV have been obtained.     

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.     

Degenerate four-wave-mixing spectroscopy in NaH

We performed DFWM spectroscopy on X ^–1+–A ¹⁺ transitions in NaH produced in an indirect photochemical reaction between Na(3p) and H₂ and detected v=1, 2 and 3 ground state vibrational levels of NaH molecules, whereas with resonance enhanced CARS, we observed v=0 levels only. This different sensitivity can be explained by considering the Franck-Condon-factors and the relevant damping coefficients for the corresponding transitions in the NaH molecule. Time resolved DFWM spectroscopy showed that NaH(v=1) molecules effectively live much longer than Na(3p) atoms which merely follow the laser excitation pulse.     

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     

Radiative Lifetimes of the Energy Levels of Palladium-like Ions Pr XIV and Nd XV

Radiative lifetimes for the 4d⁹4f, 4d⁹5p, 4d⁹5d, and 4d⁹6s levels in the spectra of palladium-like ions Pr XIV and Nd XV are calculated in the electric-dipole approximation by the intermediate coupling semiempirical method with the use of experimental energy levels available in the literature. The radial integrals of transitions necessary for calculating absolute values of transition probabilities are obtained in the length form with Hartree–Fock functions.     

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.     

Radiative lifetime and oscillator strength determination in Mg-like potassium (K VIII)

Theoretical transition probabilities have been obtained for 54 n = 3 transitions depopulating the 3s3p ¹P^o, 3p^{2 3}P, ¹D, ¹S, 3s3d ¹D, ³D and 3p3d ³P^o, ³D^o, ³F^o, ¹F^o, ¹D^o, ¹P^o levels, including 14 transitions not yet observed. Some of these predictions have been compared with experimental lifetimes obtained by beam-foil spectroscopy for four n = 3 levels of K⁷⁺. An excellent agreement is observed between theory and experiment for all the levels. Received 23 January 2002 / Received in final form 23 April 2002 Published online 19 July 2002     

Configuration interaction and radiative constants in spectra of argon-like Sc IV-Fe IX ions

The probabilities of the 3p ⁵3d, 3p ⁵4s?3p ⁶, 3p ⁵4p, 3s3p ⁶3d electric dipole transitions and radiative lifetimes of the 3p ⁵3d, 3p ⁵4p, 3p ⁵4s, and 3s3p ⁶3d levels are calculated for the Sc IV–Fe IX isoelectronic sequence.     

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     

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     

Radiative transition probabilities in ions of the silver isoelectronic sequence

The wave functions of one-electron states above the 4d ¹⁰ core have been calculated within the relativistic perturbation theory with a zero-order model potential. The wavelengths and probabilities of electric dipole transitions in an Ag-like ion have been calculated for the 5s-5p, 5p-5d, 5d-5f, and 4f-5d transitions. The data obtained are compared with the results of calculations by the relativistic Hartree-Fock method and within the relativistic many-body perturbation theory. The theoretical results are compared with experimental data on the lifetimes of energy levels in Ag-like ions.