Positron binding to calcium, a configuration interaction study

Bromley, Michael W. J.; Mitroy, Jim

doi:10.1088/0953-4075/33/9/102

Cited by 17 publications

(13 citation statements)

References 39 publications

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“…( 25). It is dominated by (Bromley and Mitroy, 2002Mitroy et al, , 2008; open circles, earlier results for these atoms and LiH molecule (Mitroy and Ryzhikh, 2000); dashed line is the fit Γ a = 5.3κ (in 10 9 s −1 ) which corresponds to F = 0.66 a.u.…”

Section: E Resonant Annihilationmentioning

confidence: 89%

“…The work by is a good review of the state of the field a few years ago. The calculations were done using a variety of methods: manybody theory and its combination with the configuration interaction (CI) (Dzuba et al, 1999(Dzuba et al, , 1995; stochastic variational method (SVM) (Ryzhikh and Mitroy, 1997;Ryzhikh et al, 1998); and the CI method with core polarization potentials (Bromley and Mitroy, 2000;.…”

Section: Positron-molecule Bindingmentioning

confidence: 99%

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Positron-molecule interactions: Resonant attachment, annihilation, and bound states

2010

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This article presents an overview of current understanding of the interaction of low-energy positrons with molecules with emphasis on resonances, positron attachment, and annihilation. Measurements of annihilation rates resolved as a function of positron energy reveal the presence of vibrational Feshbach resonances ͑VFRs͒ for many polyatomic molecules. These resonances lead to strong enhancement of the annihilation rates. They also provide evidence that positrons bind to many molecular species. A quantitative theory of VFR-mediated attachment to small molecules is presented. It is tested successfully for selected molecules ͑e.g., methyl halides and methanol͒ where all modes couple to the positron continuum. Combination and overtone resonances are observed and their role is elucidated. Molecules that do not bind positrons and hence do not exhibit such resonances are discussed. In larger molecules, annihilation rates from VFR far exceed those explicable on the basis of single-mode resonances. These enhancements increase rapidly with the number of vibrational degrees of freedom, approximately as the fourth power of the number of atoms in the molecule. While the details are as yet unclear, intramolecular vibrational energy redistribution ͑IVR͒ to states that do not couple directly to the positron continuum appears to be responsible for these enhanced annihilation rates. In connection with IVR, experimental evidence indicates that inelastic positron escape channels are relatively rare. Downshifts of the VFR from the vibrational mode energies, obtained by measuring annihilate rates as a function of incident positron energy, have provided binding energies for 30 species. Their dependence upon molecular parameters and their relationship to positron-atom and positron-molecule binding-energy calculations are discussed. Feshbach resonances and positron binding to molecules are compared with the analogous electron-molecule ͑negative-ion͒ cases. The relationship of VFR-mediated annihilation to other phenomena such as Doppler broadening of the gamma-ray annihilation spectra, annihilation of thermalized positrons in gases, and annihilation-induced fragmentation of molecules is discussed. Possible areas for future theoretical and experimental investigation are also discussed.

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Section: E Resonant Annihilationmentioning

confidence: 89%

Section: Positron-molecule Bindingmentioning

confidence: 99%

Positron-molecule interactions: Resonant attachment, annihilation, and bound states

2010

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“…The calcium atom was the first group II atom known to bind both an electron [126,127] and a positron [42]. The binding energy of the latest CI of positronic calcium was 0.016 50 Hartree [41].…”

Section: The Alkaline-earth Elements: Be Mg Ca and Srmentioning

confidence: 99%

“…This question was not answered conclusively until 1997 [31,32] when two independent calculations demonstrated the stability of positronic lithium. The initial calculations upon e + Li were quickly confirmed [33] and improved [34,35] and, in addition, many other atoms, such as Be [34,[36][37][38], Na [33,34,39], Mg [34,36,38,40,41], Ca [41,42], Sr [41], Cu [43][44][45], Zn [46,47], Ag [48,49], Cd [47,50] and metastable helium, He( 3 S e ) [13,51], have been shown to bind a positron. Besides demonstrating the existence of bound states, these calculations have offered new insights into how positrons interact with atoms and in particular have resulted in an improved understanding of the positron annihilation process.…”

Section: Introductionmentioning

confidence: 99%

Positron and positronium binding to atoms

Mitroy¹,

Bromley²,

Ryzhikh

2002

J. Phys. B: At. Mol. Opt. Phys.

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189

253

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Recent research has shown that there are a number of atoms and atomic ions that can bind a positron. The number of atoms known to be capable of binding a positron has expanded enormously in recent years, with Li, He(3 S e), Be, Na, Mg, Ca, Cu, Zn, Sr, Ag and Cd all capable of binding a positron. The structure of these systems is largely determined by the competition between the positron and the nucleus to bind the loosely bound valence electrons. Some systems, such as e + Li and e + Na, can be best described as a Ps cluster orbiting a charged Li + or Na + core, while others such as e + Be consist of a positron orbiting a polarized Be atom. In addition, a number of atoms (Li, C, O, F, Na, Cl, K, Cl, Cu, Br) can bind positronium and a few systems capable of binding two positrons have also been identified. These positron-binding systems decay by electron-positron annihilation with the annihilation rate for e + A systems largely determined by the parent atom ionization potential.

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“…Since those initial calculations, discovery of other exotic positron binding compounds has been relatively slow until 1997 when the first rigorous calculations demonstrating positron binding to a neutral atom were performed [4,5]. Since then, there have been a number of calculations of exotic positron binding compounds and numerous atoms have been shown to bind either a positron or positronium [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. This research has resulted in a greatly increased understanding about the dynamics of the interaction between positrons and atoms (and molecules).…”

Section: Introductionmentioning

confidence: 99%

Improved binding energies for LiPs, e⁺Be, NaPs and e⁺Mg

Mitroy

Ryzhikh

2001

J. Phys. B: At. Mol. Opt. Phys.

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The stochastic variational method and its fixed core variant are applied to the calculation of lithium positride (LiPs), positronic beryllium (e + Be), sodium positride (NaPs) and positronic magnesium (e + Mg). The revised binding energy of LiPs was 0.012 341 Hartree, that for e + Be was 0.031 47 Hartree, that for NaPs was 0.008 419 Hartree and the binding energy for e + Mg was 0.015 612 Hartree. The binding energies for LiPs and e + Be are expected to be within 2% of the variational limit. The uncertainties in the NaPs and e + Mg binding energies are larger and these are expected to be within 10-15% of the variational limit.

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Positron binding to calcium, a configuration interaction study

Cited by 17 publications

References 39 publications

Positron-molecule interactions: Resonant attachment, annihilation, and bound states

Positron-molecule interactions: Resonant attachment, annihilation, and bound states

Positron and positronium binding to atoms

Improved binding energies for LiPs, e⁺Be, NaPs and e⁺Mg

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Positron binding to calcium, a configuration interaction study

Cited by 17 publications

References 39 publications

Positron-molecule interactions: Resonant attachment, annihilation, and bound states

Positron-molecule interactions: Resonant attachment, annihilation, and bound states

Positron and positronium binding to atoms

Improved binding energies for LiPs, e+Be, NaPs and e+Mg

Contact Info

Product

Resources

About

Improved binding energies for LiPs, e⁺Be, NaPs and e⁺Mg