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Title: Coexistence of {alpha}+{alpha}+n+n and {alpha}+t+t cluster structures in {sup 10}Be

Abstract

The coexistence of the {alpha}+{alpha}+n+n and {alpha}+t+t cluster structures in the excited states of {sup 10}Be has been discussed. In the previous analysis, all the low-lying states of {sup 10}Be were found to be well described by the motion of the two valence neutrons around two {alpha} clusters. However, the {alpha}+t+t cluster structure was found to coexist with the {alpha}+{alpha}+n+n structure around E{sub x}=15 MeV, close to the corresponding threshold. We have introduced a microscopic model to solve the coupling effect between these two configurations. The K=0 and K=1 states are generated from the {alpha}+t+t configurations due to the spin coupling of two triton clusters. The present case of {sup 10}Be is one of the few examples in which completely different configurations of triton-type ({alpha}+t+t three-center) and {alpha}-type ({alpha}+{alpha}+n+n two-center) clusters coexist in a single nucleus in the same energy region.

Authors:
 [1];  [2];  [3]; ; ;  [4]
  1. Department of Physics, University of Tokyo, Hongo, 113-0033 Tokyo (Japan)
  2. RIKEN Nishina Center, Wako, 351-0198 Saitama (Japan)
  3. Department of Physics, University of Zagreb, HR-10000 Zagreb (Croatia)
  4. Tokai Radioactive Ion Accelerator Complex, High Energy Accelerator Research Organization (KEK), Tokai, 319-1105 Ibaraki (Japan)
Publication Date:
OSTI Identifier:
21191997
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 77; Journal Issue: 6; Other Information: DOI: 10.1103/PhysRevC.77.067301; (c) 2008 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; BERYLLIUM 10; CLUSTER MODEL; CONFIGURATION; COUPLING; EXCITED STATES; MEV RANGE; NEUTRONS; S STATES; SPIN; TRITONS; VALENCE

Citation Formats

Itagaki, N., Ito, M., Milin, M., Hashimoto, T., Ishiyama, H., and Miyatake, H.. Coexistence of {alpha}+{alpha}+n+n and {alpha}+t+t cluster structures in {sup 10}Be. United States: N. p., 2008. Web. doi:10.1103/PHYSREVC.77.067301.
Itagaki, N., Ito, M., Milin, M., Hashimoto, T., Ishiyama, H., & Miyatake, H.. Coexistence of {alpha}+{alpha}+n+n and {alpha}+t+t cluster structures in {sup 10}Be. United States. doi:10.1103/PHYSREVC.77.067301.
Itagaki, N., Ito, M., Milin, M., Hashimoto, T., Ishiyama, H., and Miyatake, H.. 2008. "Coexistence of {alpha}+{alpha}+n+n and {alpha}+t+t cluster structures in {sup 10}Be". United States. doi:10.1103/PHYSREVC.77.067301.
@article{osti_21191997,
title = {Coexistence of {alpha}+{alpha}+n+n and {alpha}+t+t cluster structures in {sup 10}Be},
author = {Itagaki, N. and Ito, M. and Milin, M. and Hashimoto, T. and Ishiyama, H. and Miyatake, H.},
abstractNote = {The coexistence of the {alpha}+{alpha}+n+n and {alpha}+t+t cluster structures in the excited states of {sup 10}Be has been discussed. In the previous analysis, all the low-lying states of {sup 10}Be were found to be well described by the motion of the two valence neutrons around two {alpha} clusters. However, the {alpha}+t+t cluster structure was found to coexist with the {alpha}+{alpha}+n+n structure around E{sub x}=15 MeV, close to the corresponding threshold. We have introduced a microscopic model to solve the coupling effect between these two configurations. The K=0 and K=1 states are generated from the {alpha}+t+t configurations due to the spin coupling of two triton clusters. The present case of {sup 10}Be is one of the few examples in which completely different configurations of triton-type ({alpha}+t+t three-center) and {alpha}-type ({alpha}+{alpha}+n+n two-center) clusters coexist in a single nucleus in the same energy region.},
doi = {10.1103/PHYSREVC.77.067301},
journal = {Physical Review. C, Nuclear Physics},
number = 6,
volume = 77,
place = {United States},
year = 2008,
month = 6
}
  • The structure of [sup 42]Ca is investigated by the [alpha]+[sup 38]Ar orthogonality condition model. The energy spectra, [alpha]-spectroscopic factors, [ital E]2 transitions, and charge form factors are analyzed. On the whole, the calculated properties are in very good agreement with the experimental data. The levels are classified into the cluster and shell-model states through the analysis of the wave functions. It is emphasized that the coexistence and interplay of cluster and shell-model states are essential to understand the properties of [sup 42]Ca.
  • It is shown that each Yakubovski component of the totally antisymmetric four-body wave function satisfies the same equation as the unantisymmetric wave function. In the antisymmetric total wave function, the wave functions belonging to the same kind of partition are totally antisymmetric among themselves. This leads to the coexistence of cluster models, including the single particle model as a special case of the cluster model, as a sum.
  • The excitation functions have been measured for the {sup 12}C ({sup 12}C,{alpha}){sup 20}Ne and {sup 12}C({sup 12}C,{sup 8}Be){sup 16}O reactions leading to the excited states up to 25 MeV in {sup 20}Ne and 20 MeV in {sup 16}O, respectively, in the beam energy range E({sup 12}C)=48{endash}72 MeV. The region of excitation investigated was E{sub x}=38{endash}50 MeV in {sup 24}Mg which is well above the threshold for breakup into six alpha particles. In the {sup 8}Be channel leading to the 6{endash}7 MeV region of {sup 16}O, excitation functions were also measured for {sup 8}Be- {gamma} coincidences in {sup 12}C ({sup 12}C,{supmore » 8}Be){sup 16}O{sup *}{r_arrow}{gamma}+{sup 16}O{sub g.s.} particularly to distinguish between the otherwise unresolved 6.05 MeV, 0{sup +} and 6.13 MeV, 3{sup {minus}} states in {sup 16}O. It is observed that a cluster of resonances in the excitation region 39{endash}43 MeV in {sup 24}Mg decays via {alpha} and {sup 8}Be channels predominantly to the particle-hole states in {sup 20}Ne and {sup 16}O which are members of deformed bands. Another cluster of resonances in the region 44{endash}49 MeV (centered at E{sub c.m.}=32.5 MeV) decays predominantly to the 20.48 MeV state in {sup 20}Ne (which is above the 5{alpha} breakup threshold) and to a possible 4{alpha} linear chain band in {sup 16}O around 18 MeV, indicating their highly deformed nature. This latter cluster structure coincides in energy with the possible 6{alpha} linear chain resonance identified in the literature at E{sub c.m.}=32.5 MeV in the inelastic scattering channels {sup 12}C{sub 7.65,0{sup +}}+{sup 12}C{sub 7.65,0{sup +}} and {sup 12}C{sub 7.65,0{sup +}}+{sup 12}C{sub 9.64,3{sup {minus}}}. In this excitation energy region intermediate structures in the {sup 8}Be channel are found at E{sub c.m.}=31.5 and 33.5 MeV decaying to the 6.13 MeV, 3{sup {minus}} state and at E{sub c.m.}=32.5 MeV decaying to the 6.92/7.13 MeV states of {sup 16}O. (Abstract Truncated)« less
  • The structure of 3/2{sup -} and 1/2{sup +} states in {sup 11}B is investigated with an {alpha}+{alpha}+t orthogonality condition model (OCM) based on the Gaussian expansion method. Full levels up to the 3/2{sub 3}{sup -} and 1/2{sub 2}{sup +} states around the {alpha}+{alpha}+t threshold (E{sub x}=11.1 MeV) are reproduced consistently with the experimental energy levels. It is shown that the 3/2{sub 3}{sup -} state located around the {sup 7}Li+{alpha} threshold has an {alpha}+{alpha}+t cluster structure, whereas the 3/2{sub 1}{sup -} and 3/2{sub 2}{sup -} states have a shell-model-like compact structure. We found that the 3/2{sub 3}{sup -} state does notmore » possess an {alpha}-condensate-like nature analogous to the 0{sub 2}{sup +} state of {sup 12}C (Hoyle state) which has a dilute 3{alpha}-condensate structure described by a (0S{sub {alpha}}){sup 3} configuration with about 70% probability, although the monopole transition strength of the former is as large as that of the latter. We discuss the reasons why the 3/2{sub 3}{sup -} state does not have the condensate character. On the other hand, the 1/2{sub 1}{sup +} state just below the {sup 7}Li+{alpha} threshold has a cluster structure that can be interpreted as a parity-doublet partner of the 3/2{sub 3}{sup -} state. We indicate that the 12.56-MeV state (J{sup {pi}}=1/2{sub 2}{sup +}) just above the {alpha}+{alpha}+t threshold observed in the {sup 7}Li({sup 7}Li,{sup 11}B{sup *})t reaction, etc., is of the dilute cluster-gas-like configuration and is a strong candidate for the product states of clusters, having a configuration of (0S{sub {alpha}}){sup 2}(0S{sub t}) with about 65% probability, from the analyses of the single-cluster motions in {sup 11}B. The structure property of the 1/2{sup +} resonant state is analyzed with the complex scaling method.« less
  • Three-nucleon transfer by the [sup 7]Li([alpha],[ital p])[sup 10]Be reaction at 65 MeV has been carried out with good resolution. A cluster model is compared to the data with the aid of zero-range distorted wave Born approximation reaction calculations, finding consistent spectroscopic factors for low-lying [ital K]=0[sup +] and 1[sup [minus]] bands. Large cluster spectroscopic factors are found for the states at 17.74 and 18.54 MeV that serve as resonances for reactions between [sup 3]H and [sup 7]Li at low energies of astrophysical importance. A research for states very near threshold found no transitions that significantly alter the important astrophysical reactionmore » rate.« less