| 1. |
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| 2. |
- Danilin, B.V., et al.
(författare)
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Three-body continuum energy correlations in Borromean halo nuclei. III. Short-range external fields
- 2007
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Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 76, s. 064612-
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Tidskriftsartikel (refereegranskat)abstract
- Energy correlations in transition from the bound state to the three-body continuum of Borromean halo nuclei are considered. A core+n+n three-body cluster model which reproduces the experimentally known properties of 6He and 11Li has been used to study the low-lying resonances and soft modes. An analysis of the correlated responses in 6He shows that in the case of the narrow 2+ resonance the transition energy correlations are the same as in the intrinsic correlated structure in 3->3 scattering. They differ significantly for wide second 2+ and first 1+ resonances, and also for the soft dipole and monopole modes, where due to the transition operators, the intertwinning of the ground state and the three-body continuum plays a significant role.
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| 3. |
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| 4. |
- Ershov, S. N., et al.
(författare)
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Binding energy constraint on matter radius and soft dipole excitations of C-22
- 2012
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Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 86:3
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Tidskriftsartikel (refereegranskat)abstract
- An unusually large value of the C-22 matter radius has recently been extracted from measured reaction cross sections. The giant size can be explained by a very loose binding that is, however, not known experimentally yet. Within the three-body cluster model we have explored the sensitivity of the s-motion-dominated C-22 geometry to the two-neutron separation energy. A low energy of a few tens of keV is required to reach the alleged experimental lower value of the matter radius, while the experimental mean radius requires an extremely tiny binding. The dependence of the C-22 charge radius on the two-neutron separation energy is also presented. The soft dipole mode in C-22 is shown to be strongly affected by the loose binding and should be studied in the process of Coulomb fragmentation.
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| 5. |
- Ershov, S. N., et al.
(författare)
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Cluster model with core excitations. The Be-11 example
- 2014
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Ingår i: Physics of Atomic Nuclei. - : Pleiades Publishing Ltd. - 1562-692X .- 1063-7788. ; 77:8, s. 989-998
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Tidskriftsartikel (refereegranskat)abstract
- Bound states and low-lying resonances of the Be-11 one-neutron halo nucleus have been calculated within a two-body cluster model with core excitation. The lowest Be-10 core excited 2(+) state was considered as a quadrupole vibration. Shallow potentials were applied for neutron-core interaction, preventing motion in Pauli forbidden orbits. A good description of available experimental data including dipole excitations of Be-11 was obtained. For the bound 1/2(-) excited state the wave-function component gives the dominant contribution to the structure, which differs from results obtained in cluster models with deep potentials.
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| 6. |
- Ershov, S. N., et al.
(författare)
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Halo formation and breakup: lessons and open questions
- 2010
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Ingår i: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 37:6
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Tidskriftsartikel (refereegranskat)abstract
- A quarter of a century's concerted international work in halo physics has resulted in an extended nuclear paradigm encompassing the limits of existence of cold nuclei and also structures beyond-continuum structures of open (nuclear) quantum systems. Realistic working models, based on cluster constituents, have sprung out of the very nature of halo phenomena, in particular from the three-body Borromean property of two-neutron halos, the lack of low-lying binary breakup channels. This has provided transparency and possibility for insight into new quantum behaviour, also in continua beyond driplines-a focus of this status assessment. Breakup spectra and progressively exclusive correlation cross sections can be computed and show, where relevant data exist, not only that general agreement is encouraging but also that some exclusive observables exhibit significant disagreement that has to be clarified. Progress in studies of two-proton emitters has provided another pathway beyond driplines, where again few-body theory appears promising.
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| 7. |
- Ershov, S. N., et al.
(författare)
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Modified variable phase method for the solution of coupled radial Schrodinger equations
- 2011
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Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 84:6
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Tidskriftsartikel (refereegranskat)abstract
- A modified variable phase method for the numerical solution of coupled radial Schrodinger equations, which maintains linear independence for different sets of solution vectors, is suggested. The modification involves rearrangement of coupled equations to avoid the usual numerical instabilities associated with components of the wave function in their classically forbidden regions. The modified method is applied to nuclear structure calculations of halo nuclei within the hyperspherical harmonics approach.
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| 8. |
- Ershov, S. N., et al.
(författare)
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New method for solution of coupled radial Schrodinger equations: application to the Borromean two-neutron halo nucleus C-22
- 2014
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Ingår i: Physics of Atomic Nuclei. - : Pleiades Publishing Ltd. - 1562-692X .- 1063-7788. ; 77:3, s. 374-383
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Tidskriftsartikel (refereegranskat)abstract
- A generalized Prufer transformation within the framework of the modified variable phase method has been used for numerical solution of coupled radial Schrodinger equations at negative energies. The method has been applied to calculations of the Borromean two-neutron halo nucleus C-22, for which an unusually large value of the matter radius has recently been extracted from measured reaction cross sections. The giant size can only be explained by an extremely loose binding that is, however, not yet known experimentally. Within the three-body cluster model we have explored the sensitivity of the C-22 matter and charge radii and soft dipole mode excitations to the two-neutron separation energy.
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| 9. |
- Ershov, S. N., et al.
(författare)
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Novel method for solution of coupled radial Schrodinger equations
- 2011
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Ingår i: Physics of Atomic Nuclei. - 1562-692X .- 1063-7788. ; 74:8, s. 1151-1161
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Tidskriftsartikel (refereegranskat)abstract
- One of the major problems in numerical solution of coupled differential equations is the maintenance of linear independence for different sets of solution vectors. A novel method for solution of radial Schrodinger equations is suggested. It consists of rearrangement of coupled equations in a way that is appropriate to avoid usual numerical instabilities associated with components of the wave function in their classically forbidden regions. Applications of the new method for nuclear structure calculations within the hyperspherical harmonics approach are given. RAMOWITZ M, 1964
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| 10. |
- Grigorenko, L. V., et al.
(författare)
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Decay mechanism and lifetime of Kr-67
- 2017
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Ingår i: Physical Review C. - 2469-9985 .- 2469-9993. ; 95:2
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Tidskriftsartikel (refereegranskat)abstract
- The lifetime of the recently discovered 2p emitter Kr-67 was found to be considerably below the lower limit predicted theoretically. This communication addresses this issue. Different separation energy systematics are analyzed and different mechanisms for 2p emission are evaluated. We find that the most plausible reason for this disagreement is the decay mechanism of 67Kr, which is not "true 2p" emission but rather "transitional dynamics" on the borderline between true 2p and sequential 2p decay mechanisms. If this is correct, this imposes stringent limits of E-r = 1.35-1.42 MeV on the ground-state energy of Br-66 relative to the Se-65-p threshold.
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| 11. |
- Grigorenko, L. V., et al.
(författare)
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Exploring the manifestation and nature of a dineutron in two-neutron emission using a dynamical dineutron model
- 2018
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Ingår i: Physical Review C. - 2469-9985 .- 2469-9993. ; 97:3
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Tidskriftsartikel (refereegranskat)abstract
- Emission of two neutrons or two protons in reactions and decays is often discussed in terms of "dineutron" or "diproton" emission. The discussion often leans intuitively on something described by Migdal-Watson approximation. In this work we propose a way to formalize situations of dineutron emission. It is demonstrated that properly formally defined dineutron emission may reveal properties which are drastically different from those traditionally expected, and properties which are actually observed in three-body decays.
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| 12. |
- Parfenova, Yu L., et al.
(författare)
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From Coulomb excitation cross sections to nonresonant astrophysical rates in three-body systems: The Ne-17 case
- 2018
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Ingår i: Physical Review C. - 2469-9985 .- 2469-9993. ; 98:3
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Tidskriftsartikel (refereegranskat)abstract
- Coulomb and nuclear dissociation of Ne-17 on light and heavy targets are studied theoretically. The dipole E1 strength function is determined in a broad energy range including energies of astrophysical interest. Dependence of the strength function on different parameters of the Ne-17 ground-state structure and continuum dynamics is analyzed in a three-body model. The discovered dependence plays an important role for studies of the strength functions for the three-body E1 dissociation and radiative capture. The constraints on the [s(2)]/[d(2)] configuration mixing in Ne-17 and on p-wave interaction in the O-15+p channel are imposed based on experimental data for Ne-17 Coulomb dissociation on heavy target.
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| 13. |
- Shulgina, N. B., et al.
(författare)
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Superhalo of C 22 reexamined
- 2018
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Ingår i: Physical Review C. - 2469-9985 .- 2469-9993. ; 97:6
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Tidskriftsartikel (refereegranskat)abstract
- An unusually large value of the C22 matter radius, extracted by Tanaka et al. [Phys. Rev. Lett. 104, 062701 (2010)PRLTAO0031-900710.1103/PhysRevLett.104.062701] from measured reaction cross sections, attracted great attention of scientific community. Since that time, several experimental works related to the C22 nucleus have appeared in the literature. Some of the experimental data, measured with high accuracy, allow us to fix C22 structure more reliably. Two limiting models reproducing C22 nuclear structure within the three-body cluster approach, that allow us to describe all existing experimental data, are presented. The C22 ground state, continuum structure, and geometry are obtained. With fixed C22 wave function, the prediction for the soft dipole mode in C22, which is studied in the process of Coulomb fragmentation, is performed.
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| 14. |
- Vaagen, J.S., et al.
(författare)
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Lessons from two paradigmatic developments; Rutherford's nuclear atom and halo nuclei
- 2012
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 381:1, s. Art. no. 012049-
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Konferensbidrag (refereegranskat)abstract
- In its initial 1911 version, underpinned by discoveries in alpha-scattering experiments, Rutherford's atom model made a gross separation of neutral matter; A veil of light negative matter surrounding a tiny impenetrable heavy positive core. The model had however little to say about the atomic (electronic) architecture and dynamics, hence did not make it straight to the catwalk of physics of those days. Three quarters of a century later, in 1985, new discoveries in collision experiments revealed existence of abnormally large light nuclei, but could say less about the nuclear architecture. History sometimes repeats itself: Like Bohr's ad hoc planetary model (1913) changed the fate of Rutherford's discovery, again Scandinavian inspired ideas on architecture, this time nuclear halos, changed our paradigm for the heart of matter. We comment on the need for a concerted Rutherfordian effort between theory and increasingly complete reaction experiments if further ground-breaking progress is going to be made in halo physics, and physics in vicinities of neutron and proton driplines, and generally in the more widely growing field of many-body open quantum systems, where structure and reactions come together. © Published under licence by IOP Publishing Ltd.
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| 15. |
- Vaagen, J.S., et al.
(författare)
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Paradigmatic lessons from nuclear driplines
- 2015
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Ingår i: Nuclear Physics: Present and Future. - Cham : Springer International Publishing. - 9783319101996 ; , s. 69-78
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Science is—as emphasized 50 years ago by ThomasKuhn in his academic bestseller The Structure of Scientific Revolutions—driven by paradigms, rooted in outstanding discoveries and practice. At the centennial for the nuclear atom, it may be appropriate to address the current paradigmatic situation for nuclear physics on background of the large investmentsmade during the last decades. Following Rutherford’s paradigm, nuclear physics has developed by colliding nuclei and from studying the fragments that emerge. With restriction to new forms of transient cold nuclear matter, we will address if and how new discoveries have influenced the way we think about nuclear architecture, drawing parallels with comparable development in other branches of science. Recent discoveries in halo nuclei,11Be and the Borromean22C will serve as our cardinal examples. The challenges at driplines may appear less dramatic than what calls for a Kuhnian turnover, still we hope to convey that valuable lessons may be learned. The attention-grabbing dripline lessons we address are rooted in emergent degrees of freedom involving cluster constituents. This is a great challenge for the ruling paradigm, a shell-model inspired ab initio nucleon-based theory, developed and tested for stable nuclei, and currently being tuned to encompass dripline lessons. Our mental pictures and dynamic understanding of many of the outstanding dripline phenomena will, however, remain linked to cluster degrees of freedom. This duality makes our paradigmatic lessons conceptually less dramatic than what Kuhn’s “incommensurability” may imply.
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