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Resonances with natural and unnatural parities in positron-sodium scattering
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
2015 (English)In: Physical Review A, ISSN 2469-9926, Vol. 92, 012706Article in journal (Refereed) Published
Abstract [en]

We present an investigation of resonances in positron-sodium scattering using the complex scaling method. For the target sodium atoms, the interaction between the core and outer electron is treated using two different types of analytical model potentials. Explicitly correlated Gaussian wave functions are used to represent the correlation effects between the outer electron, the positron, and the Na+ core. S-, P-, and D-wave resonances with natural parity have been calculated for energies extending up to the positronium n = 2 formation threshold. Resonance states for unnatural parities Pe and D0 have been calculated for energies extending up to the positronium n = 3 threshold. Below both positronium thresholds we have for each symmetry identified a dipole series of resonances, with binding energies scaling in good agreement with expectations from an analytical calculation. The presented results are compared with other theoretical calculations.

Place, publisher, year, edition, pages
2015. Vol. 92, 012706
National Category
Physical Sciences
Research subject
Theoretical Physics
Identifiers
URN: urn:nbn:se:su:diva-124120DOI: 10.1103/PhysRevA.92.012706OAI: oai:DiVA.org:su-124120DiVA: diva2:882217
Available from: 2015-12-14 Created: 2015-12-14 Last updated: 2016-04-11Bibliographically approved
In thesis
1. Resonances in Three-Body Systems
Open this publication in new window or tab >>Resonances in Three-Body Systems
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Three particles interacting via Coulomb forces represent a fundamental problem in quantum mechanics with no known exact solution. We have investigated resonance states composed of three particles interacting via Coulombic and more general potentials in non-relativistic quantum mechanics, using the complex scaling method. Our calculations have been applied to three different systems.

(i) An investigation of resonances in the positron-alkali (Li, Na, K) systems has been conducted. Some calculations have previously been reported on the resonances in positron-alkali systems; however, most of the work was limited to the lower partial wave, such as S-wave resonances. In this thesis, we have extended the calculations to higher partial waves and extracted the resonance positions and widths using the more accurate complex scaling method. A dipole series of resonances has been found under positronium n = 2 threshold, for natural parity and n = 3 threshold for unnatural parity states. Furthermore, these resonances were found to agree well with an analytically derived scaling law. This series in the positron-alkali system are caused by the attractive potential formed by the dipole moment of positronium (the bound state of an electron and a positron). This dipole moment is a hydrogen-like system, and hence its energy levels are degenerate with respect to orbital angular momentum. We have also predicted several new resonances.

(ii) A calculation of resonances in positron-hydrogen scattering, which shows that we can represent this system with the accuracy needed for future scattering calculations. Such cross sections are of interest since this is a way to form anti-hydrogen.

(iii) A search for possible resonances in the pµe system, which has been suggested as a possible reason for unexpected results from a recent measurement of the proton radius in muonic hydrogen. We have ruled out the possibility of such resonances.

In all calculations we used the Couple Rearrangement Channel Method, where the wave function is represented by Gaussians expressed in Jacobi coordinates. Thus effects due to mass polarization are automatically.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2016. 44 p.
National Category
Atom and Molecular Physics and Optics
Research subject
Theoretical Physics
Identifiers
urn:nbn:se:su:diva-128860 (URN)978-91-7649-408-0 (ISBN)
Public defence
2016-05-27, sal FB52, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: Submitted. Paper 6: Submitted.

 

Available from: 2016-05-02 Created: 2016-04-06 Last updated: 2016-05-06Bibliographically approved

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Umair, MuhammadJonsell, Svante
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