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arXiv 1207.7191nucl-th
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低激发态$^{12}$ Be共振的三体性质

Three-body properties of low-lying $^{12}$Be resonances

E. Garrido, A. S. Jensen, D. V. Fedorov, J. G. Johansen

备注：
To be published in Physical Review C
发表信息：
Physical Review C 86, 024310 (2012)
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摘要：

我们计算了$^{12}$ Be最低共振态的三体结构，把它看作是两个中子围绕惰性$^{10}$ Be核的情况。这是将$^{12}$ Be的束缚态计算推广到连续谱中。我们研究了角动量和宇称的最低共振态，$0^{\pm}$，$1^{-}$和$2^{+}$。令人惊讶的是，它们都是在三体模型中自然发生的。我们计算了由小距离性质主导的体结构以及由渐近大距离结构决定的衰变。$0^{+}$和$2^{+}$都具有二体$^{10}$ Be中子d波结构，而$1^{-}$具有$p$和d波的均匀混合。相应的相对中子-中子分波分布在$s$、$p$和d波之间。分支比显示了单中子发射、三体直接衰变和连续衰变的不同混合。我们讨论了自旋和宇称$0^{+}$、$1^{-}$和$2^{+}$分别在0.89、2.03、5.13处的共振。计算的结构与现有的反应测量是一致的。

英文摘要：

We compute the three-body structure of the lowest resonances of $^{12}$Be considered as two neutrons around an inert $^{10}$Be core. This is an extension of the bound state calculations of $^{12}$Be into the continuum spectrum. We investigate the lowest resonances of angular momenta and parities, $0^{\pm}$, $1^{-}$ and $2^{+}$. Surprisingly enough, they all are naturally occurring in the three-body model. We calculate bulk structure dominated by small distance properties as well as decays determined by the asymptotic large-distance structure. Both $0^{+}$ and $2^{+}$ have two-body $^{10}$Be-neutron d-wave structure, while $1^{-}$ has an even mixture of $p$ and d-waves. The corresponding relative neutron-neutron partial waves are distributed among $s$, $p$, and d-waves. The branching ratios show different mixtures of one-neutron emission, three-body direct, and sequential decays. We argue for spin and parities, $0^{+}$, $1^{-}$ and $2^{+}$, to the resonances at 0.89, 2.03, 5.13, respectively. The computed structures are in agreement with existing reaction measurements.

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