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| 2. |
- Andersson, Martin, et al.
(författare)
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HFSZEEMAN - A program for computing weak and intermediate field fine and hyperfine structure Zeeman splittings from MCDHF wave functions
- 2008
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Ingår i: Computer Physics Communications. - : Elsevier BV. - 0010-4655 .- 1879-2944. ; 178:2, s. 156-170
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Tidskriftsartikel (refereegranskat)abstract
- Given electronic wave functions generated by the grasp2K relativistic atomic structure package, this program calculates diagonal magnetic dipole A(J) and electric quadrupole B-J hyperfine interaction constants and Lande g(J) factors. In addition the program computes diagonal and off-diagonal reduced hyperfine and Zeeman matrix elements and constructs the total interaction matrix for an atom in an external magnetic field. By diagonalizing the interaction matrix and plotting eigenvalues as functions of the magnetic field, Zeeman splittings of hyperfine levels are obtained. The method is applicable in the weak and intermediate field regions and yields results that are useful when analyzing spectra from e.g. EBIT sources and magnetic stars. The program can also be used in the field free limit to calculate mixing coefficients that determine rates of hyperfine induced transitions. For atoms with zero nuclear spin I the program computes splittings of the fine-structure levels. Program summary Program title: HFSZEEMAN Catalogue identifier: ADZS_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADZS-v1-0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 1528 No. of bytes in distributed program, including test data, etc.: 294 664 Distribution format: tar.gz Programming language: Fortran, Matlab Computer: IBM-compatible PC, unix workstation Operating system: Unix, Linux Classification: 11.6 Subprograms used: Cat Id: ADZL_v1_0; Title: grasp2K v1.0; Reference: CPC 177 (2007) 597 Nature of problem: Prediction of weak and intermediate field Zeeman splittings of fine- and hyperfine structure levels using multiconfiguration Dirac-Hartree-Fock wave functions. Solution method: The electronic wave function for a state labeled Gamma JM is expanded in terms of jj-coupled configuration state functions vertical bar Gamma JM > = Sigma(gamma)c(gamma)vertical bar gamma JM >. In this representation the reduced matrix elements used to construct the interaction matrix can be computed as sums over one-particle radial integrals. By diagonalizing the interaction matrix and plotting eigenvalue as functions of the magnetic field, Zeeman splittings of fine- and hyperfine structure levels are obtained. Restrictions: The complexity of the cases that can be handled is entirely determined by the grasp2K package [P. Jonsson, H. Xe, C. Froese Fischer, I.P. Grant, Comput. Phys. Commun. 177 (2007) 597] used for the generation of the electronic wave functions. Running time: CPU time required to execute test cases: a few seconds.
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| 3. |
- Andersson, Martin, et al.
(författare)
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HYPERFINE-DEPENDENT gf -VALUES OF Mn i LINES IN THE 1.49–1.80 μm H BAND
- 2015
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Ingår i: The Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 216:1
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Tidskriftsartikel (refereegranskat)abstract
- The three Mn I lines at 17325, 17339, and 17349 angstrom are among the 25 strongest lines (log(gf) > 0.5) in the H band. They are all heavily broadened due to hyperfine structure, and the profiles of these lines have so far not been understood. Earlier studies of these lines even suggested that they were blended. In this work, the profiles of these three infrared (IR) lines have been studied theoretically and compared to experimental spectra to assist in the complete understanding of the solar spectrum in the IR. It is shown that the structure of these lines cannot be described in the conventional way using the diagonal A and B hyperfine interaction constants. The off-diagonal hyperfine interaction not only has a large impact on the energies of the hyperfine levels, but also introduces a large intensity redistribution among the hyperfine lines, changing the line profiles dramatically. By performing large-scale calculations of the diagonal and off-diagonal hyperfine interaction and the gf-values between the upper and lower hyperfine levels and using a semi-empirical fitting procedure, we achieved agreement between our synthetic and experimental spectra. Furthermore, we compare our results with observations of stellar spectra. The spectra of the Sun and the K1.5 III red giant star Arcturus were modeled in the relevant region, 1.73-1.74 mu m, using our theoretically predicted gf-values and energies for each individual hyperfine line. Satisfactory fits were obtained and clear improvements were found using our new data compared with the old available Mn I data. A complete list of energies and gf-values for all the 3d(5)4s(S-7)4d e(6)D - 3d(5)4s(S-7)4f w(6)F hyperfine lines are available as supporting material, whereas only the stronger lines are presented and discussed in detail in this paper.
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| 4. |
- Andersson, Martin, et al.
(författare)
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Hyperfine induced interference effects in the 4s4d 3D2–4s4f 3F2,3 transitions in Ga II
- 2006
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Ingår i: Journal of Physics B. - : Bibliopolis, Edizioni di Filosofia e Scienze. - 0953-4075 .- 1361-6455. ; 39:20, s. 4239-4247
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Tidskriftsartikel (refereegranskat)abstract
- We report relativistic multiconfiguration Dirac–Hartree–Fock calculations of transitions between the hyperfine levels of 4s4f 3F2,3 and 4s4d 3D2 in Ga II. The capacity of two newly developed programs connected to the graspVU package for generating synthetic spectra is explored. The obtained theoretical spectra are compared to Fourier transform spectra and good agreement is found. The importance of hyperfine induced interference effects for the 4s4d 3D2–4s4f 3F2 transitions is pointed out, and the gf values for all the hyperfine transitions are given.
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| 5. |
- Aourir, Nouria, et al.
(författare)
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Theoretical hyperfine structures of F-19 I and O-17 I
- 2018
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society. - 2469-9926 .- 2469-9934. ; 97:3
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Tidskriftsartikel (refereegranskat)abstract
- Multiconfiguration Hartree-Fock (MCHF) and multiconfiguration Dirac-Hartree-Fock (MCDHF) calculations are performed for the 2p(5) P-2 degrees, 2p(4)(P-3)3s P-4, 2p(4)(P-3)3s P-2, and 2p(4)(P-3)3 p S-4 degrees states of F-19 I to determine their hyperfine constants. Several computing strategies are considered to investigate electron correlation and relativistic effects. High-order correlation contributions are included in MCHF calculations based on single and double multireference expansions. The largest components of the single reference MCHF wave functions are selected to define the multireference (MR) sets. In this scheme, relativistic corrections are evaluated in the Breit-Pauli approximation. A similar strategy is used for the calculation of MCDHF relativistic wave functions and hyperfine parameters. While correlation and relativistic corrections are found to be rather small for the ground state, we highlight large relativistic effects on the hyperfine constant A(3/2) of 2p(4)(P-3)3 p(4)S(degrees) and, to a lesser extent, on A(1/2) of 2p(4)(P-3)3s P-4. As expected for such a light system, electron correlation effects dominate over relativity in the calculation of the hyperfine interaction of all other levels considered. We also revisit the hyperfine constants of 2p(3)((4)(S))3s S-5 degrees and 2p(3)(S-4)3 p P-5 in O-17 using similar strategies. The results are found to be in excellent agreement with experiment.
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| 6. |
- Atalay, B., et al.
(författare)
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MCDHF and RCI calculations of energy levels, lifetimes, and transition rates in Si III and Si IV
- 2019
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 631
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Tidskriftsartikel (refereegranskat)abstract
- We present extensive multiconfiguration Dirac-Hartree-Fock and relativistic configuration interaction calculations including 106 states in doubly ionized silicon (Si III) and 45 states in triply ionized silicon (Si IV), which are important for astrophysical determination of plasma properties in different objects. These calculations represents an important extension and improvement of earlier calculations especially for Si III. The calculations are in good agreement with available experiments for excitation energies, transition properties, and lifetimes. Important deviations from the NIST-database for a selection of perturbed Rydberg series are discussed in detail.
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| 7. |
- Beck, P S A, et al.
(författare)
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A ground-validated NDVI dataset for monitoring vegetation dynamics and mapping phenology in Fennoscandia and the Kola peninsula
- 2007
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Ingår i: International Journal of Remote Sensing. - : Informa UK Limited. - 1366-5901 .- 0143-1161. ; 28:19, s. 4311-4330
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Tidskriftsartikel (refereegranskat)abstract
- An NDVI dataset covering Fennoscandia and the Kola peninsula was created for vegetation and climate studies, using Moderate Resolution Imaging Spectroradiometer 16-day maximum value composite data from 2000 to 2005. To create the dataset, ( 1) the influence of the polar night and snow on the NDVI values was removed by replacing NDVI values in winter with a pixel- specific NDVI value representing the NDVI outside the growing season when the pixel is free of snow; and ( 2) yearly NDVI time series were modelled for each pixel using a double logistic function defined by six parameters. Estimates of the onset of spring and the end of autumn were then mapped using the modelled dataset and compared with ground observations of the onset of leafing and the end of leaf fall in birch, respectively. Missing and poor-quality data prevented estimates from being produced for all pixels in the study area. Applying a 5 km x 5 km mean filter increased the number of modelled pixels without decreasing the accuracy of the predictions. The comparison shows good agreement between the modelled and observed dates ( root mean square error = 12 days, n = 108 for spring; root mean square error = 10 days, n = 26, for autumn). Fennoscandia shows a range in the onset of spring of more than 2 months within a single year and locally the onset of spring varies with up to one month between years. The end of autumn varies by one and a half months across the region. While continued validation with ground data is needed, this new dataset facilitates the detailed monitoring of vegetation activity in Fennoscandia and the Kola peninsula.
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| 8. |
- Bengtsson, Peter, et al.
(författare)
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Energy structure and transition rates in the Ne-like sequence from relativistic CI calculations
- 2012
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Ingår i: Europhysics Conference Abstracts;36C. - : European Physical Society. ; , s. 128-128
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Atomic data are important in astrophysical applications and transition rates can be used in the determination of element abundances and plasma diagnostics. To provide for the extensive data needs a number of general computer codes such as SUPERSTRUCTURE, CIV3, and ATSP2K have been developed. As an alternative to these codes, which all rely on the Breit-Pauli approximation, the fully relativistic GRASP2K code can be used. GRASP2K is based on the multiconfiguration Dirac-Hartree-Fock method and implements a bi-orthogonal transformation method that permits initial and final states in a transition array to be optimized separately, which, in many cases, leads to more accurate values of the resulting rates. The GRASP2K package also contains modules to compute diagonal and off-diagonal hyperfine interaction constants, isotope shifts, Land´e gJ factors, and splittings of magnetic sub-state in intermediate and strong magnetic fields. In this work, GRASP2K has been applied to provide highly accurate spectroscopic data for ions in the Ne-like sequence between Mg III and Kr XXVII. Valence, core-valence, and core-core correlation effects were accounted for through SD-MR expansions to increasing sets of active orbitals. In Mg III, Al IV, Si V, P VI, S VII, and Ar IX, for which experimental energies are known to high accuracy, the mean error in the calculated energies is only 0.011%. For ions with no available experimental energy levels the calculated values should be most valuable in various applications. The high accuracy of the calculated energies makes it possible, in some cases, to to point out experimental values that are in error. Babushkin (length) and Coulomb (velocity) forms of transition rates are computed and agree to within a few percent for the majority of the allowed transitions. Computed lifetimes for states belonging to the 2p33s and 2p53d configurations are in good agreement with values from beam-foil measurements as well as from accurate MCHF Breit-Pauli calculations.
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| 9. |
- Bieron, Jacek, et al.
(författare)
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Ab initio calculations of the hyperfine structure of zinc and evaluation of the nuclear quadrupole moment Q(Zn-67)
- 2018
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society. - 2469-9926 .- 2469-9934. ; 97:6
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Tidskriftsartikel (refereegranskat)abstract
- The relativistic multiconfiguration Dirac-Hartree-Fock and the nonrelativistic multiconfiguration Hartree-Fock methods have been employed to calculate the magnetic dipole and electric quadrupole hyperfine structure constants of zinc. The calculated electric field gradients for the 4s4p P-3(1)degrees and 4s4p P-3(2)degrees states, together with experimental values of the electric quadrupole hyperfine structure constants, made it possible to extract a nuclear electric quadrupole moment Q((67) Zn) = 0.122(10) b. The error bar was evaluated in a quasistatistical approach-the calculations were carried out with 11 different methods, and then the error bar was estimated from the differences between the results obtained with those methods.
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| 10. |
- Bieron, Jacek, et al.
(författare)
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Ab initio MCDHF calculations of electron-nucleus interactions
- 2015
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Ingår i: Physica Scripta. - : Institute of Physics Publishing (IOPP). - 0031-8949 .- 1402-4896. ; 90:5
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Tidskriftsartikel (refereegranskat)abstract
- We present recent advances in the development of atomic ab initio multiconfiguration Dirac– Hartree–Fock theory, implemented in the GRASP relativistic atomic structure code. For neutral atoms, the deviations of properties calculated within the Dirac–Hartree–Fock (DHF) method (based on independent particle model of an atomic cloud) are usually dominated by electron correlation effects, i.e. the non-central interactions of individual electrons. We present the recent advances in accurate calculations of electron correlation effects in small, medium, and heavy neutral atoms. We describe methods of systematic development of multiconfiguration expansions leading to systematic, controlled improvement of the accuracy of the ab initio calculations. These methods originate from the concept of the complete active space (CAS) model within the DHF theory, which, at least in principle, permits fully relativistic calculations with full account of electron correlation effects. The calculations within the CAS model on currently available computer systems are feasible only for very light systems. For heavier atoms or ions with more than a few electrons, restrictions have to be imposed on the multiconfiguration expansions. We present methods and tools, which are designed to extend the numerical calculations in a controlled manner, where multiconfiguration expansions account for all leading electron correlation effects. We show examples of applications of the GRASP code to calculations of hyperfine structure constants, but the code may be used for calculations of arbitrary bound-state atomic properties. In recent years it has been applied to calculations of atomic and ionic spectra (transition energies and rates), to determinations of nuclear electromagnetic moments, as well as to calculations related to interactions of bound electrons with nuclear electromagnetic moments leading to violations of discrete symmetries.
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