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Atoms
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Positron Scattering and Annihilation with Atoms and Molecules including Emerging...
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Positron Scattering and Annihilation with Atoms and Molecules including Emerging New Resonances and their Applications in other Systems

A special issue of Atoms (ISSN 2218-2004).

Deadline for manuscript submissions: closed (31 January 2016) | Viewed by 39082

Special Issue Editors

Prof. Dr. Chi Yu Hu

E-Mail Website
Guest Editor
California State University, Long Beach, Department of Physics & Astronomy, 1250 Bellflower Blvd., Long Beach, CA 90840-3901, USA
Interests: Multichannel Faddeev-Merkuriev equation (MFE); Gailitis resonances (internal Stark resonances); practical applications of the Gailitis
Dr. Anand K. Bhatia

E-Mail Website
Guest Editor
Heliophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA
Interests: scattering and annihilation of positrons and electrons; Feshbach resonances; photoionization of atoms; muonic physics; Rydberg states; excitation of ions by electron and proton impact and their applications to astrophysics; photoionization; atomic structure calculations; Lamb shift
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The low energy positron collisions and annihilation on atoms and molecules has had a long and very successful research record in both theoretical and experimental fronts. At energy above the positronium formation threshold, the progress was limited due to the inability to distinguish the direct positron annihilation from that due to positronium formation. This problem is solved beginning with the three-body scattering systems using the multi-channel Faddeev-Merkuriev equation (MFE). The complete solution of a six-open channel (S-partial wave) positron collision with hydrogen atom system provided detail information of the structures of resonances. Two types of resonances exist in this region. One type is identified as the well known Feshbach resonances. The second type has been identified to have a much different formation mechanism. It is named the Gailitis resonances. A series of Gailitis resonances occur when the incoming charged particle and the target atom with electric moments become correlated at certain distances via the internal Stark-effect. The life-time of these resonances can be very long when the center of mass collision energy is small. Such long-lived long range correlation can produce interesting physical effects. An earlier six-open channel, S-partial waves calculation showed enhanced anti-hydrogen formation cross section from the incoming channel anti-proton + positronium atom around the energy region of the Gailitis resonances. Recent theoretical calculation indicated the Gailitis resonance is able to provide an alternative route to muon catalyzed fusion. Low energy nuclear fusion can be explained when the condition for the formation of Gailitis resonance exists. The physical mechanism involved in the formation of Gailitis resonance is the universal Stark-effect. This Special Issue hopes to bring awareness of the Gailitis resonance to the larger physics communities. We invite authors to submit articles from all areas of physics.

Dr. Chiyu Hu
Dr. Anand K. Bhatia
Guest Editors

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Published Papers (8 papers)

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Research

433 KiB  
Article
Positron-Hydrogen Scattering, Annihilation, and Positronium Formation
by Anand K. Bhatia
Atoms 2016, 4(4), 27; https://doi.org/10.3390/atoms4040027 - 4 Nov 2016
Cited by 11 | Viewed by 4715
Abstract
In previous papers (Bhatia A.K. 2007, 2012) a hybrid theory for the scattering of electrons from a hydrogenic system was developed and applied to calculate scattering phase shifts, Feshbach resonances, and photoabsorption processes. This approach is now being applied to the scattering of [...] Read more.
In previous papers (Bhatia A.K. 2007, 2012) a hybrid theory for the scattering of electrons from a hydrogenic system was developed and applied to calculate scattering phase shifts, Feshbach resonances, and photoabsorption processes. This approach is now being applied to the scattering of positrons from hydrogen atoms. Very accurate phase shifts, using the Feshbach projection operator formalism, were calculated previously (Bhatia A.K. et al. 1971 and Bhatia et al. 1974a). The present results, obtained using shorter expansions in the correlation function, along with long-range correlations in the Schrödinger equation, agree very well with the results obtained earlier. The scattering length is also calculated and the present results are compared with the previous results. Annihilation cross-sections, and positronium formation cross-sections, calculated in the distorted-wave approximation, are also presented. Full article
(This article belongs to the Special Issue Positron Scattering and Annihilation with Atoms and Molecules including Emerging New Resonances and their Applications in other Systems)
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1725 KiB  
Article
Series of Broad Resonances in Atomic Three-Body Systems
by Daniel Diaz, Zoltan Papp and Chi-Yu Hu
Atoms 2016, 4(2), 17; https://doi.org/10.3390/atoms4020017 - 20 Jun 2016
Viewed by 3507
Abstract
We re-examine the series of resonances found earlier in atomic three-body systems by solving the Faddeev-Merkuriev integral equations. These resonances are rather broad and line up at each threshold with gradually increasing gaps. This lining up takes place in the same way for [...] Read more.
We re-examine the series of resonances found earlier in atomic three-body systems by solving the Faddeev-Merkuriev integral equations. These resonances are rather broad and line up at each threshold with gradually increasing gaps. This lining up takes place in the same way for all thresholds and is irrespective of the spatial symmetry. We relate these resonances to the Gailitis mechanism, which is a consequence of the polarization potential. Full article
(This article belongs to the Special Issue Positron Scattering and Annihilation with Atoms and Molecules including Emerging New Resonances and their Applications in other Systems)
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269 KiB  
Communication
The Faddeev-Merkuriev Differential Equations (MFE) and Multichannel 3-Body Scattering Systems
by Chi Yu Hu
Atoms 2016, 4(2), 16; https://doi.org/10.3390/atoms4020016 - 3 May 2016
Cited by 1 | Viewed by 4423
Abstract
Numerical implementation of the modified Faddeev Equation (MFE) is presented in some detail. The Faddeev channel wave function displays unique properties of each and every open channel, respectively. In particular, near resonant energies, the structures of the resonances are beautifully displayed, from which, [...] Read more.
Numerical implementation of the modified Faddeev Equation (MFE) is presented in some detail. The Faddeev channel wave function displays unique properties of each and every open channel, respectively. In particular, near resonant energies, the structures of the resonances are beautifully displayed, from which, the life-time of the resonances can be determined by simply using the uncertainty principle. The phase shift matrix, or the K-matrix, provides unique information for each and every resonance. This information enables the identification of the physical formation mechanism of the Gailitis resonances. A few of these resonances, previously known as the mysterious shape resonances, have occurred in a number of different collision systems. The Gailitis resonances are actually produced by a quantized Stark-effect within the various collision systems. Since the Stark-effect is a universal phenomenon, the Gailitis resonances are expected to occur in much broader classes of collision systems. We will present the results of a precision calculation using the MFE method in sufficient detail for interested students who wish to explore the mysteries of nature with a powerful theoretical tool. Full article
(This article belongs to the Special Issue Positron Scattering and Annihilation with Atoms and Molecules including Emerging New Resonances and their Applications in other Systems)
4755 KiB  
Article
Relativistic Ionization of Hydrogen Atoms by Positron Impact
by Amal Chahboune, Bouzid Manaut, Elmostafa Hrour and Souad Taj
Atoms 2016, 4(1), 10; https://doi.org/10.3390/atoms4010010 - 4 Mar 2016
Cited by 1 | Viewed by 4393
Abstract
Relativistic triple differential cross-sections (TDCS) for ionization of hydrogen atoms by positron impact have been calculated in the symmetric coplanar geometry. We have used Dirac wave functions to describe free electron’s and positron’s sates. The relativistic formalism is examined by taking the non [...] Read more.
Relativistic triple differential cross-sections (TDCS) for ionization of hydrogen atoms by positron impact have been calculated in the symmetric coplanar geometry. We have used Dirac wave functions to describe free electron’s and positron’s sates. The relativistic formalism is examined by taking the non relativistic limit. Present results are compared with those for the corresponding electron-impact case. In the first Born approximation, we found that the TDCS for positron impact ionization exceeds that for electron impact for all energies in accordance with the result obtained by several other theories. Full article
(This article belongs to the Special Issue Positron Scattering and Annihilation with Atoms and Molecules including Emerging New Resonances and their Applications in other Systems)
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Graphical abstract

1140 KiB  
Article
Merkuriev Cut-off in e+ − H Multichannel Scattering Calculations
by Vitaly A. Gradusov, Vladimir A. Roudnev and Sergey L. Yakovlev
Atoms 2016, 4(1), 9; https://doi.org/10.3390/atoms4010009 - 1 Mar 2016
Cited by 5 | Viewed by 4291
Abstract
We present the results of positron-Hydrogen multichannel scattering calculations performed on the base of Faddeev-Merkuriev equations. We discuss an optimal choice of the Merkuriev’s Coulomb splitting parameters. Splitting the Coulomb potential in two-body configuration space is applicable for a limited energy range. Splitting [...] Read more.
We present the results of positron-Hydrogen multichannel scattering calculations performed on the base of Faddeev-Merkuriev equations. We discuss an optimal choice of the Merkuriev’s Coulomb splitting parameters. Splitting the Coulomb potential in two-body configuration space is applicable for a limited energy range. Splitting the potential in three-body configuration space makes it possible to perform calculations in a broader range of energies and to optimize the numerical convergence. Scattering cross sections for zero total angular momentum for all processes between the positronium formation threshold and the third excitation threshold of the Hydrogen atom are reported. Full article
(This article belongs to the Special Issue Positron Scattering and Annihilation with Atoms and Molecules including Emerging New Resonances and their Applications in other Systems)
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720 KiB  
Article
Second Order Stark-Effect Induced Gailitis Resonances in e + Ps and p + 7Li
by Chi Yu Hu and Zoltan Papp
Atoms 2016, 4(1), 8; https://doi.org/10.3390/atoms4010008 - 26 Feb 2016
Cited by 2 | Viewed by 6123
Abstract
We present a detailed comparison between the first order Stark-effect induced Gailitis resonance in e+ + H (n = 2) and the second order Stark-effect induced resonance in e + Ps (n = 1). Common characteristics as well as differences [...] Read more.
We present a detailed comparison between the first order Stark-effect induced Gailitis resonance in e+ + H (n = 2) and the second order Stark-effect induced resonance in e + Ps (n = 1). Common characteristics as well as differences of these resonances will be identified. These results will be used to assess the presence of Gailitis resonances in the scattering of proton on the ground state of 7Li atom. During the lifetime of the Gailitis resonance, nuclear fusion is enhanced by the resonant entry of the proton into the nucleus of 7Li via a compound nuclear energy level of 8Be*. Full article
(This article belongs to the Special Issue Positron Scattering and Annihilation with Atoms and Molecules including Emerging New Resonances and their Applications in other Systems)
5725 KiB  
Article
Natural and Unnatural Parity Resonance States in the Positron-Hydrogen System with Screened Coulomb Interactions
by Ye Ning, Zong-Chao Yan and Yew Kam Ho
Atoms 2016, 4(1), 3; https://doi.org/10.3390/atoms4010003 - 26 Dec 2015
Cited by 13 | Viewed by 5611
Abstract
In the present work, we report calculations of resonances in the positron-hydrogen system interacting with screened Coulomb potentials using the method of complex scaling together with employing correlated Hylleraas wave functions. Resonances with natural and unnatural parities are investigated. For the natural parity [...] Read more.
In the present work, we report calculations of resonances in the positron-hydrogen system interacting with screened Coulomb potentials using the method of complex scaling together with employing correlated Hylleraas wave functions. Resonances with natural and unnatural parities are investigated. For the natural parity case, resonance parameters (energy and width) for D-wave resonance states with even parity lying below various positronium and hydrogen thresholds up to the H(N = 4) level are determined. For the unnatural parity case, results for P-even and D-odd resonance states with various screened Coulomb interaction strengths are located below different lower-lying Ps and H thresholds. Full article
(This article belongs to the Special Issue Positron Scattering and Annihilation with Atoms and Molecules including Emerging New Resonances and their Applications in other Systems)
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389 KiB  
Article
Quantum Entanglement and Shannon Information Entropy for the Doubly Excited Resonance State in Positronium Negative Ion
by Chien-Hao Lin and Yew Kam Ho
Atoms 2015, 3(3), 422-432; https://doi.org/10.3390/atoms3030422 - 21 Sep 2015
Cited by 10 | Viewed by 4854
Abstract
In the present work, we report an investigation on quantum entanglement in the doubly excited 2s2 1Se resonance state of the positronium negative ion by using highly correlated Hylleraas type wave functions, determined by calculation of the density of resonance [...] Read more.
In the present work, we report an investigation on quantum entanglement in the doubly excited 2s2 1Se resonance state of the positronium negative ion by using highly correlated Hylleraas type wave functions, determined by calculation of the density of resonance states with the stabilization method. Once the resonance wave function is obtained, the spatial (electron-electron orbital) entanglement entropies (von Neumann and linear) can be quantified using the Schmidt decomposition method. Furthermore, Shannon entropy in position space, a measure for localization (or delocalization) for such a doubly excited state, is also calculated. Full article
(This article belongs to the Special Issue Positron Scattering and Annihilation with Atoms and Molecules including Emerging New Resonances and their Applications in other Systems)
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