Dipole Transition Probabilities Research Articles

A theoretical survey of atomic structure and forbidden transitions in the 4pk and 4dk ground configurations of tungsten ions W29 + through W43 +

Energy levels, wavelengths and radiative decay rates have been calculated for states within the 4pk (k = 1–5) and 4dk (k = 1–9) ground configurations in highly charged tungsten ions. Magnetic dipole (M1) and electric quadrupole (E2) transition probabilities have been obtained using the fully relativistic multiconfiguration Dirac–Fock (MCDF) approach including the correlations within the n = 4 complex, some n = 4 → n′ = 5 single excitations and quantum electrodynamics effects. The validity of the method is assessed through limited comparison with experimental and theoretical data previously published as well as with new relativistic Hartree–Fock calculations. The excellent agreement observed between our new MCDF A-values and those obtained using different theoretical approaches together with a detailed analysis of configuration interaction effects does not confirm the very recent GRASP2K calculations of Jonauskas et al (2012 At. Data Nucl. Data Tables 98 19) for M1 lines within the 4dk configurations, the latter results remaining in large disagreement with all other methods in many cases.

Multiconfiguration Dirac-Fock results for forbidden transitions in the 2p 4 configuration

Abstract Relativistic configuration interaction calculations with the inclusion of the Breit interaction, quantum electrodynamics and finite nuclear mass corrections have been carried out in the extended optimal level scheme using multiconfiguration Dirac-Fock wavefunctions on the forbidden transition probabilities for the 2p 4 ground state configuration of the oxygen isoelectronic sequence for 8 ⩽ Z ⩽ 42. Electric quadrupole and magnetic dipole transition probabilities are reported for transitions between several of these levels. Our results are compared with those from other theories and experiments. Our energy levels are in better agreement with experiment than other theories.

Electric Dipole Transitions for Lu I (Z = 71)

The aim of this study was to obtain a description of the neutral lutetium spectrum. We calculated the radiative parameters (wavelengths, weighted oscillator strengths and transition probabilities) for electric dipole (E1) transitions for some excited levels in neutral lutetium (Lu I, Z = 71). Two configuration interaction methods were used: the multiconfiguration Hartree–Fock method developed by Fischer within the Breit-Pauli relativistic framework (MCHF + BP), and Cowan’s relativistic Hartree–Fock (HFR) method. Results obtained have been compared with each other and with other works. A discussion of these calculations for Lu I in this study has also been in view of the MCHF + BP and HFR methods.

Transition probabilities, oscillator strengths and lifetimes for singly ionized magnesium

The electric dipole transition probabilities, oscillator strengths and lifetimes have been calculated using the weakest bound electron potential model theory (WBEPMT) for singly ionized magnesium. In the calculations both multiplet and fine structure transitions are studied. We have employed both the numerical Coulomb approximation (NCA) method and numerical non-relativistic Hartree–Fock (NRHF) wave functions for expectation values of radii. The calculated oscillator strengths and lifetimes have been compared with MCHF results given by Fischer et al. (2006). A good agreement has been obtained with the MCHF results. Moreover, some new transition probabilities, oscillator strengths and lifetime values, not existing in the data bases for highly excited levels in singly ionized magnesium, have been obtained using this method.

LaVO 4 : Eu Phosphor films with enhanced Eu solubility

Eu doped rare-earth orthovanadates are known to be good red phosphor materials. In particular, LaVO4:Eu is a promising candidate due to the low Eu-site point symmetry, and thus high dipole transition probability within Judd–Ofelt theory. However, the low solubility limit (<3 mol %) of Eu in LaVO4 prevents its efficient use as a phosphor. We present optical evidence of enhanced Eu solubility as high as 10 mol % in LaVO4:Eu thin films grown by pulsed laser deposition and postannealing. The photoluminescent intensity exceeded that of YVO4:Eu thin films when excited below the host bandgap, indicating stronger direct emission of Eu in LaVO4.

Relativistic configuration interaction calculations on Kα x-ray satellites of krypton

The multi-configuration Dirac–Fock (MCDF) and relativistic configuration interaction (RCI) methods have been used for computing the transition wavelengths, electric dipole transition probabilities, line strengths and absorption oscillator strengths for the Kα x-rays from Kr XXVII to Kr XXXV. The contributions from Breit interaction, finite nuclear mass corrections and quantum electrodynamics corrections to the initial and final levels have been taken into account. The calculated values showed good agreement between these results and recent theoretical and experimental results. These data provide reference values for the level lifetimes, charge state distribution and average charge of krypton plasmas.

Transition probabilities for 5s–5p, 5p–5d, 4f–5d, and 5d–5f transitions in Ag-like ions with Z = 50–86

The wavelengths, electric dipole transition probabilities, and oscillator strengths are calculated for transitions between low-lying states (5s–5p, 5p–5d, 4f–5d, and 5d–5f) in the silver isoelectronic sequence (50 ⩽ Z ⩽ 86) using relativistic perturbation theory with a zero-approximation model potential. The results are compared with the corresponding data of the relativistic Hartree–Fock theory and the relativistic many-body perturbation theory. The results of these three theoretical approaches are compared with available experimental data for the level lifetimes. Possible reasons for some disagreements are discussed.

New atomic data for Ti X

A large-scale configuration interaction (CI) calculation using CIV3 is performed for the 303 fine-structure levels of the aluminum-like titanium ion. We have calculated the energy levels, oscillator strengths, and transition probabilities for the electric dipole allowed and intercombination transitions among the levels of ground state 3s 23p ( 2p o) and higher energy levels of states 3s3p 2, 3p 3, 3s3p3d, 3p 23d, 3s 24s, 3s3d 2, 3s 24p, 3s3p4s, 3s3p4p, 3p3d 2, 3s3p4d, 3s3p4f, 3s 25p, 3p 24p, 3s3d4s, 3s3p5s, 3s3d4p, 3s3p5p, 3s 2(4d, 4f, 5s, 5d, 5f, 6s, 6p, 6d, 6f) of Ti X in the LSJ coupling scheme. The calculations include all the major correlation effects. We attempt to correct the inaccuracies in the CI coefficients in the wavefunctions, which would lead to inaccuracies in transition probabilities by applying a “fine-tuning” technique. The relativistic effects are incorporated by adding the mass correction, Darwin, and spin–orbit interaction terms into the non-relativistic Hamiltonian in the Breit–Pauli approximation. The present results are in good agreement with other available calculations and experiments. Several new lines corresponding to 3s3p nl ( n = 4, 5 and l = 0, 1), 3s 25p, 3s 2(6s, 6p) and other configurations are predicted where no other theoretical or experimental results are available. We expect that our extensive calculations will be useful to experimentalists in identifying the fine-structure levels in their future work.

ANALYSIS OF BREIT–PAULI TRANSITION PROBABILITIES FOR LINES IN O III

Accurate atomic data are essential for understanding the properties of both O III lines produced by the Bowen fluorescence mechanism and [O III] forbidden lines observed in numerous gaseous nebulae. Improved Breit-Pauli transition probabilities have been published for the carbon sequence. Included were revised data for O III. The present paper analyzes the accuracy of the data specifically for O III by comparison with other theory as well as some recent experiments and observations. For the electric dipole transition probabilities, good agreement is found for allowed Bowen fluorescence lines between predictions of intensity ratios with observed data. For forbidden transitions, the Breit-Pauli magnetic dipole transition operator requires corrections that often are neglected. Good agreement is found when these transition probabilities are computed with multiconfiguration Dirac-Hartree-Fock methods.

Radiative transition probabilities in ions of the silver isoelectronic sequence

The wave functions of one-electron states above the 4d10 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.

Identification of van Hove singularities in the GaN dielectric function: a comparison of the cubic and hexagonal phase

AbstractWe present a detailed analysis of interband transition structures in the dielectric function of GaN. The dielectric function of the stable wurtzite and the metastable zinc blende phase were determined by means of synchrotron spectroscopic ellipsometry in the spectral range between 3 eV and 20 eV where the most significant structures of the dielectric function are located. In the hexagonal case, both the ordinary and extraordinary dielectric tensor component was measured on GaN films with M ‐plane/[1 $ \bar 1 $00] orientation. In a comparative discussion of the two hexagonal tensor components and the zinc blende dielectric function, all prominent absorption structures were assigned to specific interband transitions at high symmetry points in the Brillouin zone. The assignment considers the individual dipole transition probabilities depending on the crystal symmetry and the geometry of the measurement. Furthermore, a detailed theoretical band‐to‐band analysis of dielectric function features, published by Lambrecht et al. [1], was considered. In conclusion, we suggest a new labeling of absorption structures as used in classical III–V materials like GaAs, which reflects the origin of transition structures from specific points in the respective Brillouin zones. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Multiconfiguration Dirac-Hartree-Fock energy levels and transition probabilities for 3d5in Fe iv

Multiconfiguration Dirac-Hartree-Fock electric quadrupole (E2) and magnetic dipole (M1) transition probabilities are reported for transitions between levels of 3d 5 in [Fe iv]. The accuracy of the ab initio energy levels and the agreement in the length and velocity forms of the line strength for the E2 transitions are used as indicators of accuracy. The present E2 and Ml transition probabilities are compared with earlier Breit-Pauli results and other theories. An extensive set of transition probabilities with indicators of accuracy are reported in Appendices A and B. Recommended values of A(E2) + A(M1) are listed in Appendix C.

Decay Pattern of Pygmy States Observed in Neutron-RichNe26

Coulomb excitation of the exotic neutron-rich nucleus (26)Ne on a (208)Pb target was measured at 58 MeV/u in order to search for low-lying E1 strength above the neutron emission threshold. This radioactive beam experiment was carried out at the RIKEN Accelerator Research Facility. Using the invariant mass method in the 25Ne+n channel, we observe a sizable amount of E1 strength between 6 and 10 MeV excitation energy. By performing a multipole decomposition of the differential cross section, a reduced dipole transition probability of B(E1)=0.49+/-0.16e(2) fm(2) is deduced, corresponding to 4.9+/-1.6% of the Thomas-Reiche-Kuhn sum rule. For the first time, the decay pattern of low-lying strength in a neutron-rich nucleus is measured. The extracted decay pattern is not consistent with several mean-field theory descriptions of the pygmy states.

Atomic data and electron-impact broadening effect in DO white dwarf atmospheres: Si vi

Energy levels, electric dipole transition probabilities and oscillator strengths in five times ionized silicon have been calculated in intermediate coupling. The present calculations were carried out with the general purpose atomic structure program superstructure. The relativistic corrections to the non-relativistic Hamiltonian are taken into account through the Breit–Pauli approximation. We have also introduced a semi-empirical correction [term energy corrections (TEC)] for the calculation of the energy levels. These atomic data are used to provide semiclassical electron-, proton- and ionized helium-impact linewidths and shifts for 15 Si vi multiplet. Calculated results have been used to consider the influence of Stark broadening for DO white dwarf atmospheric conditions.

Electric dipole transitions for La I ( Z=57)

Wavelengths, weighted oscillator strengths and transition probabilities for electric dipole ( E1) transitions for some excited levels in neutral lanthanum (La I, Z=57) have been calculated using the multiconfiguration Hartree–Fock (MCHF) method within the framework of Breit–Pauli relativistic corrections. Results obtained have been compared with other calculations and experiments. A discussion of these calculations for La I in this study has also been given in view of the MCHF method.

Probabilities of radiative dipole transitions of parahelium in an electric field

Quadratic Stark corrections to the wave functions, matrix elements, and probabilities of transitions between the singlet states 1S0 and 1P1 of helium atoms are calculated. The coefficients of the polynomials that depend on the effective principal quantum number of the upper level vf and that approximate the numerical values of the polarizabilities, the quadratic corrections to the wave functions, and the probabilities of transitions to highly excited Rydberg states with large vf are determined. The results of calculations testify that the probabilities of all σ transitions ni1S0 → nf1P1 and π transitions to the states with nf > ni/2 are decreased with increasing electric field strength, except for the transition 21S0 → 21P1, whose probability increases both for σ and for π transitions.

Electric dipole transitions for highly excited states in helium-like sulphur

We have calculated relativistic energies, weighted oscillator strengths and transition probabilities for electric dipole (E1) transitions among the terms belonging to 1 snl ( n⩽9, l⩽3) configurations in helium-like sulphur. The calculations are based upon the multiconfiguration Hartree–Fock method within the framework of Breit–Pauli relativistic corrections. Our calculated values are also compared with other experimental and theoretical results.

Branching ratios of radiative transitions in O VI

We study the branching ratios of the allowed and forbidden radiative transitions among the first few (9) fine structure levels of O VI using relativistic coupled-cluster theory. We find irregular patterns for a number of transitions within n-complexes with n ⩽ 4. We have used the existing values of the allowed electric dipole (E1) transition as a benchmark of our theory. Good agreement with the existing values establish accuracies of not only the theoretical method but the basis function as well. In general, the electric quadrupole (E2) transition probabilities are greater in magnitude than magnetic dipole (M1) transition probabilities, whereas for medium atomic transition frequencies they are of the same order of magnitude. On the other hand, if the transitions involved are in between two fine-structure components of the same term, then the M1 transition probability is more probable than that of E2. The results presented here in tabular and graphical form are compared with the available theoretical and observed data. Graphical analysis helps to understand the trends of electric and magnetic transitions for the decay channels presented here. Our calculated values of the lifetimes of the excited states are in very good agreement with the available results.

Search for low lying dipole strength in the neutron rich nucleus 26Ne

Coulomb excitation of the exotic neutron-rich nucleus 26 Ne on a nat Pb target was measured at 58 A.MeV in order to search for low-lying E1 strength above the neutron emission threshold. Data were also taken on an nat Al target to estimate the nuclear contribution. The radioactive beam was produced by fragmentation of a 95 A.MeV 40 Ar beam delivered by the RIKEN Research Facility. The set-up included a NaI gamma-ray array, a charged fragment hodoscope and a neutron wall. Using the invariant mass method in the 25 Ne+n channel, we observe a sizable amount of E1 strength between 6 and 10 MeV. The reconstructed 26 Ne angular distribution confirms its E1 nature. A reduced dipole transition probability of B ( E 1 ) = 0.49 ± 0.16 e 2 fm 2 is deduced. For the first time, the decay pattern of low-lying strength in a neutron-rich nucleus is obtained. The results are discussed in terms of a pygmy resonance centered around 9 MeV.

Deformation parameters and transition probabilities for shears bands in Pb isotopes

Tilt angles, deformation parameters, angular momenta, and reduced magnetic dipole and electric quadrupole transition probabilities are calculated within the framework of the tilted-axis cranking model for shears bands in the neutron-deficient Pb isotopes $^{193}\mathrm{Pb}$ to $^{202}\mathrm{Pb}$. The self-consistently calculated quadrupole-deformation parameters for the various configurations lie around ${\ensuremath{\varepsilon}}_{2}=\ensuremath{-}0.1$, and the triaxiality is small. The tilt angle, i.e., the angle between the angular momentum and the nuclear symmetry axis, remains almost constant within each band, showing only a small increase toward higher angular momenta. The angular momentum increases mainly due to the shears effect, which is a step-by-step alignment of high-$j$ proton and neutron orbitals into the direction of the total angular momentum. Calculated and experimental $M1$ transition rates are in good agreement. They decrease with increasing spin within the bands as expected for the shears effect. The calculated $B(E2)$ values show only a weak spin dependence. However, the experimental $B(E2)$ values have large errors, and more accurate data are needed to decide between the present model and a recently suggested geometrical approach.