Cluster formations in deformed states for<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">Si</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>28</mml:mn></mml:mrow></mml:mmultiscripts></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">S</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>32</mml:mn></mml:mrow></mml:mmultiscripts></mml:mat

Ichikawa, Takatoshi; Kanada-En’yo, Yoshiko; Möller, P.

doi:10.1103/physrevc.83.054319

Phys. Rev. C

2011

DOI: 10.1103/physrevc.83.054319

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Cluster formations in deformed states forSi28andS32

Takatoshi Ichikawa

Yoshiko Kanada-En’yo

P. Möller

Abstract: We study cluster formation in strongly deformed states for 28 Si and 32 S using a macroscopic-microscopic model. The study is based on calculated total-energy surfaces, which are the sums of deformation-dependent macroscopic-microscopic potential-energy surfaces and rotational-energy contributions. We analyze the angular-momentum-dependent total-energy surfaces and identify the normal-and super-deformed states in 28 Si and 32 S, respectively. We show that at sufficiently high angular momenta strongly deformed … Show more

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Cited by 29 publications

(82 citation statements)

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“…A number of recent studies based on nuclear EDFs or the mean-field approach have analysed cluster structures in α-conjugate nuclei [15][16][17][18][19][20][21]. In Fig.…”

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confidence: 99%

How atomic nuclei cluster

Ebran

Khan

Nikšić

et al. 2012

Nature

169

244

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Nucleonic matter displays a quantum liquid structure, but in some cases finite nuclei behave like molecules composed of clusters of protons and neutrons. Clustering is a recurrent feature in light nuclei, from beryllium to nickel. For instance, in 12 C the Hoyle state, crucial for stellar nucleosynthesis, can be described as a nuclear molecule consisting of three alpha-particles. The mechanism of cluster formation, however, has not yet been fully understood. We show that the origin of clustering can be traced back to the depth of the confining nuclear potential. By employing the theoretical framework of energy density functionals that encompasses both cluster and quantum liquid-drop aspects of nuclei, it is shown that the depth of the potential determines the energy spacings between single-nucleon orbitals, the localization of the corresponding wave functions and, therefore, the degree of nucleonic density clustering. Relativistic functionals, in particular, are characterized by deep single-nucleon potentials. When compared to non-relativistic functionals that yield similar ground-state properties (binding energy, deformation, radii), they predict the occurrence of much more pronounced cluster structures. More generally, clustering is considered as a transitional phenomenon between crystalline and quantum liquid phases of fermionic systems.The occurrence of molecular states in atomic nuclei and the formation of clusters of nucleons were already predicted in the 30's by von Weizsäcker and Wheeler [1,2]. Even though the description of nuclear dynamics became predominantly based on the concept of independent nucleons in a mean-field potential, a renewed interest in clustering phenomena in the 60's led to the development of dedicated theoretical methods [3]. Numerous experimental studies have revealed a wealth of data on clustering phenomena in light nuclei [4], and modern theoretical approaches use microscopic models that fully take into account single-nucleon degrees of freedom [5][6][7]. Clustering gives rise to nuclear molecules. For instance, in 12 C the second 0 + state the Hoyle state that plays a critical role in stellar nucleosynthesis, is predicted to display a three-α structure [8,9]. The binding energy of the α-particle, formed from two protons and two neutrons, is much larger than in other light nuclei. Cluster radioactivity [10], discovered in the 80's, is another manifestation of clustering in atomic nuclei. Experimental signatures of clustering are usually indirect. Quasi-molecular resonances are probed by scattering one cluster on another, such as in the 12 C+ 12 C system [4,11], and cluster structures are also discernible in the breakup of nuclei. Evidence has been reported for the formation of clusters in ground and excited states of a number of α-conjugate nuclei [4], that is nuclei with an equal even number of protons and neutrons, from 8 Be to 56 Ni.The mechanism of cluster formation in nuclei has not yet been fully understood. Deformation plays an important role because it removes the degenera...

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“…A number of recent studies based on nuclear EDFs or the mean-field approach have analysed cluster structures in α-conjugate nuclei [15][16][17][18][19][20][21]. In Fig.…”

mentioning

confidence: 99%

How atomic nuclei cluster

Ebran

Khan

Nikšić

et al. 2012

Nature

169

244

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“…The enhancement of the transition strength would correspond to the development of such cluster structure. In this respect, gas-like two α states around an 16 O core in 24 Mg have been investigated both theoretically [15,[17][18][19] and experimentally [16,20,21].…”

mentioning

confidence: 99%

“…In analogy to the three α-particle Hoyle state in 12 C, the existence of states, similar to the Hoyle state with three α-particles around an 16 O core can be expected. However, in 28 Si, many strongly coupled cluster states would emerge at and below/above the ( 16 O + 3α) decay threshold energy [22][23][24]. Three α particles around an 16 O core would form the strongly coupled 12 C state, to gain the inter cluster potential energy.…”

mentioning

confidence: 99%

“…We calculate the excited states in 28 Si using the multi-configuration mixing method based on the 16 O + 3α cluster model. We also include the 16 O + 12 C and 24 Mg + α basis wave functions prepared by the generator coordinate method. To identify the gas-like states, we calculate the isoscalar monopole transition strengths and the overlap of the obtained states with the geometrical cluster wave function and the TohsakiHoriuchi-Schuck-Röpke (THSR) wave function.…”

mentioning

confidence: 99%

“…We superpose many randomly generated Slater determinants, which correspond to the multiconfiguration mixing (MCM) method. To describe the molecular states, we also include the basis wave functions with 16 O + 12 C and 24 Mg + α configurations prepared by the generator coordinate method (GCM). In the MCM calculations, it becomes often difficult to identify the structure of the obtained results as the number of the basis wave functions increases, because many states couple with each other.…”

mentioning

confidence: 99%

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Search for three-αstates around an16O core in28Si

et al. 2012

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We investigate the existence of weakly coupled gas-like states comprised of three α particles around an 16 O core in 28 Si. We calculate the excited states in 28 Si using the multi-configuration mixing method based on the 16 O + 3α cluster model. We also include the 16 O + 12 C and 24 Mg + α basis wave functions prepared by the generator coordinate method. To identify the gas-like states, we calculate the isoscalar monopole transition strengths and the overlap of the obtained states with the geometrical cluster wave function and the TohsakiHoriuchi-Schuck-Röpke (THSR) wave function. The results show that the obtained fourth and twelfth states significantly overlap with the THSR wave function. These two states clearly coexist with the 16 O + 12 C cluster states, emerging at similar energies. The calculated isoscalar monopole strengths between those two states are significantly large, indicating that the states are members of the excitation mode. Furthermore, the calculated root-mean-squared (RMS) radii for these states also suggest that a layer of gas-like three α particles could exist around the surface of the 16 O core, which can be described as a "two-dimensional gas" in the intermediate state before the Hoyle-like three α states emerge. 21.60.Gx,27.20.+n,27.30.+t The investigations of excited states in light-mass nuclei provide a good opportunity to study the rich variety of nuclear structures of quantum many-body systems. One of these states is the well known Hoyle state in 12 C * [1]. The Hoyle state is the second 0 + state in 12 C * , with an excitation energy of 7.65 MeV, just above the 3 α decay threshold energy. Many theoretical attempts have been performed to reproduce its energy and geometrical properties. It was found, that it is difficult to reproduce those values by calculations based only on the shell model. On the other hand, the microscopic three α cluster models successfully describe the properties of the Hoyle state (such as the observed α-decay width) and indicate that the three α state develops well in the 0 + 2 state [2,3]. Recent calculations, using the α cluster model suggest that in the Hoyle state, the three "gas-like" α particles are weakly coupled with each other at near the three α-decay threshold energy [4,5]. Based on this picture, the Tohsaki-HoriuchiSchuck-Röpke (THSR) wave function was proposed. This wave function describes the α particles as independent, with their center-of-mass motion, in the same 0S state of the harmonic oscillator, having a large oscillator parameter. Using this wave function, Tohsaki et al. proposed the extremely large RMS nuclear radius for the 0 + 2 state in 12 C [4]. Those studies have triggered interest in whether such gaslike states exist in heavier-mass nuclei. Funaki et al. searched for gas-like four α states in 16 O * using the microscopic α cluster model coupled with the THSR wave function [6,7]. In this connection, the existence of weakly coupled gas-like α cluster states around a core has been recently suggested [8][9][10][11][12]. To study...

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¹²C+¹⁶O sub-barrier radiative capture cross-section measurements

Goasduff

Courtin

Haas

et al. 2011

EPJ Web of Conferences

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Abstract.We have performed a heavy ion radiative capture reaction between two light heavy ions, 12 C and 16 O, leading to 28 Si. The present experiment has been performed below Coulomb barrier energies in order to reduce the phase space and to try to shed light on structural effects. Obtained γ-spectra display a previously unobserved strong feeding of intermediate states around 11 MeV at these energies. This new decay branch is not fully reproduced by statistical nor semi-statistical decay scenarii and may imply structural effects. Radiative capture cross-sections are extracted from the data.

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Cluster formations in deformed states forSi28andS32

Cited by 29 publications

References 46 publications

How atomic nuclei cluster

How atomic nuclei cluster

Search for three-αstates around an16O core in28Si

¹²C+¹⁶O sub-barrier radiative capture cross-section measurements

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Cluster formations in deformed states forSi28andS32

Cited by 29 publications

References 46 publications

How atomic nuclei cluster

How atomic nuclei cluster

Search for three-αstates around an16O core in28Si

12C+16O sub-barrier radiative capture cross-section measurements

Contact Info

Product

Resources

About

¹²C+¹⁶O sub-barrier radiative capture cross-section measurements