| 1. |
- Grumer, Jon, et al.
(författare)
-
Magnetic field induced transition rates in Ne- and Be-like ions for plasma diagnostics and E1M1 two-photon decay rate determination
- 2014
-
Ingår i: XXVIII International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2013). - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 488, s. 152005-152005
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We report on theoretical results of magnetic field induced transitions (MITs) in Ne- and Be-like ions without nuclear spin for two applicalions. Firstly, MITs are promising candidates in the determination of magnetic fields in plasmas. In our work on Ne-like ions we present accurate theoretical MIT rates for 2p(6 1)S(O) - 2p(5)3s 3P(O),2 [11. Purthermore, for Be-like ions, it has been proposed to extract the rate of the BIM1 two-photon transition 2s(2 1)S(O) - 2s2p P-3(O) by measuring the lifetime of the 'Po state using a storage ring, which involves an external magnetic field. The MIT rates are carefully evaluated and shown to be of the same order as the ElMI rates [2].
|
|
| 2. |
- Grumer, Jon, et al.
(författare)
-
Magnetic field induced transition rates in Ne- and Be-like ions for plasma diagnostics and E1M1 two-photon decay rate determination
- 2013
-
Ingår i: Book of abstracts. - : Institute of Modern Physics, Chinese Academy of Sciences.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Synopsis We report on theoretical results of magnetic field induced transitions (MITs) in Ne- and Be-like ions without nuclear spin for two applications. Firstly, MITs are promising candidates in the determination of magnetic fields in plasmas. In our work on Ne-like ions we present accurate theoretical MIT rates for 2p6 1S0 − 2p53s 3P0 , 2 [1]. Furthermore, for Be-like ions, it has been proposed to extract the rate of the E1M1 two-photon transition 2s2 1S0 − 2s2p 3P0 by measuring the lifetime of the 3P0 state using a storage ring, which involves an external magnetic field. The MIT rates are carefully evaluated and shown to be of the same order as the E1M1 rates.
|
|
| 3. |
- Grumer, Jon, et al.
(författare)
-
The effect of an external magnetic field on the determination of E1M1 two-photon decay rates in Be-like ions
- 2013
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 88
-
Tidskriftsartikel (refereegranskat)abstract
- In this work we report on ab initio theoretical results for the magnetic-field-induced 2s 2p 3P0 → 2s2 1S0 E1 transition for ions in the beryllium isoelectronic sequence between Z = 5 and 92. It has been proposed that the rate of the E1M1 two-photon transition 2s 2p 3P0 → 2s2 1S0 can be extracted from the lifetime of the 3P0 state in Be-like ions with zero nuclear spin by employing resonant recombination in a storage ring. This experimental approach involves a perturbing external magnetic field. The effect of this field needs to be evaluated in order to properly extract the two-photon rate from the measured decay curves. The magnetic-field-induced transition rates are carefully evaluated, and it is shown that, with a typical storage-ring field strength, it is dominant or of the same order as the E1M1 rate for low- and mid-Z ions. Results for several field strengths and ions are presented, and we also give a simple Z-dependent formula for the rate. We estimate the uncertainties of our model to be within 5% for low- and mid-Z ions and slightly larger for more highly charged ions. Furthermore we evaluate the importance of including both perturber states, 3P1 and 1P1, and it is s
|
|
| 4. |
- Grumer, Jon, et al.
(författare)
-
Unexpected transitions induced by spin-dependent, hyperfine and external magnetic-field interactions
- 2014
-
Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 89:11
-
Tidskriftsartikel (refereegranskat)abstract
- Unexpected transitions are induced by weaker interactions not included in the gross structure model of the ion under investigation. We discuss different examples of such decay channels, starting with relativistic spin-induced transitions. These represented an important field of study a few decades ago, and we illustrate how some challenging cases can be treated very accurately with today's computational techniques, while close degeneracy sometimes still prevents ab initio methods from obtaining accurate results. For hyperfine induced transitions we review some recent results and discuss remaining challenges for experiment and theory. Finally, we discuss the newly opened field of accurate calculations for transitions induced by an external magnetic field and point to some examples of where these are accessible for experimental tests.
|
|
| 5. |
|
|
| 6. |
- Jönsson, Per, et al.
(författare)
-
An Introduction to Relativistic Theory as Implemented in GRASP
- 2023
-
Ingår i: Atoms. - : MDPI. - 2218-2004. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- Computational atomic physics continues to play a crucial role in both increasing the understanding of fundamental physics (e.g., quantum electrodynamics and correlation) and producing atomic data for interpreting observations from large-scale research facilities ranging from fusion reactors to high-power laser systems, space-based telescopes and isotope separators. A number of different computational methods, each with their own strengths and weaknesses, is available to meet these tasks. Here, we review the relativistic multiconfiguration method as it applies to the General Relativistic Atomic Structure Package [grasp2018, C. Froese Fischer, G. Gaigalas, P. Jonsson, J. Bieron, Comput. Phys. Commun. (2018). DOI: 10.1016/j.cpc.2018.10.032]. To illustrate the capacity of the package, examples of calculations of relevance for nuclear physics and astrophysics are presented.
|
|
| 7. |
- Jönsson, Per, et al.
(författare)
-
GRASP Manual for Users
- 2023
-
Ingår i: Atoms. - : MDPI. - 2218-2004. ; 11:4
-
Tidskriftsartikel (refereegranskat)abstract
- grasp is a software package in Fortran 95, adapted to run in parallel under MPI, for research in atomic physics. The basic premise is that, given a wave function, any observed atomic property can be computed. Thus, the first step is always to determine a wave function. Different properties challenge the accuracy of the wave function in different ways. This software is distributed under the MIT Licence.
|
|
| 8. |
- Li, Jiguang, et al.
(författare)
-
Theoretical investigation of magnetic-field-induced 2p(5)3s 3P(0,2)-2p(6) S-1(0) transitions in Ne-like ions without nuclear spin
- 2013
-
Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 88:1
-
Tidskriftsartikel (refereegranskat)abstract
- We report theoretical results for magnetic-field-induced 2p(5)3s 3P(0,2)-2p(6) S-1(0) E1 transitions in Ne-like ions with zero nuclear spin (I = 0) between Mg III and Zn XXI as well as in Ne I. We demonstrate that it is important to include both "perturber" states 2p(5)3s P-1(1) and 2p(5)3s P-3(1) in order to produce reliable transition rates. Furthermore, we investigate the trends of the rates along the isoelectronic sequence of the 2p(5)3s 3P(0,2)-2p(6) S-1(0) transitions and their competition with the 2p(5)3s P-3(0)-2p(5)3s P-3(1) M1 and the 2p(5)3s P-3(2)-2p(6) S-1(0) M2 decays. For the 2p(5)3s P-3(0) state the magnetic-field-induced transition becomes the dominant decay channel for the light elements even in a relatively weak magnetic field, and it will therefore prove useful in diagnostics of the strength of magnetic fields in different plasmas. The influence of an external magnetic field on the lifetime of the 2p(5)3s P-3(2) state is much smaller but still observable for the ions near the neutral end of the sequence. As a special case, the magnetic field effect on the lifetimes of 2p(5)3s P-3(0,2) states of neutral Ne-20 is discussed. It is found that the lifetimes are drastically reduced by a magnetic field, which may be an underlying reason for the discrepancies in the lifetime of the 2p(5)3s P-3(2) state between experiment [14.73(14) s] and theory (17.63 s).
|
|
| 9. |
- Li, Jiguang, et al.
(författare)
-
Theoretical investigation of magnetic-field-induced 2p53s 3P0 - 2p6 1S0 transitions in Ne-like ions without nuclear spin
- 2013
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 88:1
-
Tidskriftsartikel (refereegranskat)abstract
- We report theoretical results for magnetic-field-induced 2p53s 3P0,2 − 2p6 1S0 E1 transitions in Ne-like ions with zero nuclear spin (I = 0) between Mg III and Zn XXI as well as in Ne I.We demonstrate that it is important to include both “perturber” states 2p53s 1P1 and 2p53s 3P1 in order to produce reliable transition rates. Furthermore, we investigate the trends of the rates along the isoelectronic sequence of the 2p53s 3P0,2 − 2p6 1S0 transitions and their competition with the 2p53s 3P0 − 2p53s 3P1 M1 and the 2p53s 3P2 − 2p6 1S0 M2 decays. For the 2p53s 3P0 state the magnetic-field-induced transition becomes the dominant decay channel for the light elements even in a relatively weak magnetic field, and it will therefore prove useful in diagnostics of the strength of magnetic fields in different plasmas. The influence of an external magnetic field on the lifetime of the 2p53s 3P2 state is much smaller but still observable for the ions near the neutral end of the sequence. As a special case, the magnetic field effect on the lifetimes of 2p53s 3P0,2 states of neutral 20Ne is discussed. It is found that the lifetimes are drastically reduced by a magnetic field, which may be an underlying reason for the discrepancies in the lifetime of the 2p53s 3P2 state between experiment [14.73(14) s] and theory (17.63 s).
|
|
| 10. |
- Li, Yanting, et al.
(författare)
-
Fine-Tuning of Atomic Energies in Relativistic Multiconfiguration Calculations
- 2023
-
Ingår i: Atoms. - : MDPI. - 2218-2004. ; 11:4
-
Tidskriftsartikel (refereegranskat)abstract
- Ab initio calculations sometimes do not reproduce the experimentally observed energy separations at a high enough accuracy. Fine-tuning of diagonal elements of the Hamiltonian matrix is a process which seeks to ensure that calculated energy separations of the states that mix are in agreement with experiment. The process gives more accurate measures of the mixing than can be obtained in ab initio calculations. Fine-tuning requires the Hamiltonian matrix to be diagonally dominant, which is generally not the case for calculations based on jj-coupled configuration state functions. We show that this problem can be circumvented by a method that transforms the Hamiltonian in jj-coupling to a Hamiltonian in LSJ-coupling for which fine-tuning applies. The fine-tuned matrix is then transformed back to a Hamiltonian in jj-coupling. The implementation of the method into the General Relativistic Atomic Structure Package is described and test runs to validate the program operations are reported. The new method is applied to the computation of the 2s(21)S(0)-2s2p(1,3)P(1) transitions in C III and to the computation of Rydberg transitions in B I, for which the 2s(2)p(22)S(1/2) perturber enters the 2s(2)ns(2)S(1/2) series. Improved convergence patterns and results are found compared with ab initio calculations.
|
|
