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論文

Experimental study of the $$Gamma_{p1}/Gamma_{p0}$$ ratios of resonance states in $$^{8}$$Be for deducing the $$^{7}$$Be($$n$$,$$p_{1}$$)$$^{7}$$Li$$^{*}$$ reaction rate relevant to the cosmological lithium problem

岩佐 直仁*; 石川 竣喜*; 久保野 茂*; 榊原 昂浩*; 小湊 和也*; 西尾 勝久; 松田 誠; 廣瀬 健太郎; 牧井 宏之; Orlandi, R.; et al.

Physical Review C, 103(1), p.015801_1 - 015801_5, 2021/01

https://doi.org/10.1103/PhysRevC.103.015801
 被引用回数：1 パーセンタイル：18.12(Physics, Nuclear)

The $$^{9}$$Be($$^{3}$$He,$$alpha$$)$$^{8}$$Be($$p$$)$$^{7}$$Li reaction was studied at $$E_{rm lab}$$($$^{3}$$He)=30 MeV to deduce the branching ratios of $$Gamma_{p1}/Gamma_{p0}$$ of resonant state at 18.91 - 20.1 MeV in $$^{8}$$Be, which are necessary to extract the $$^{7}$$Be($$n$$, $$p_{1}$$)$$^{7}$$Li$$^{*}$$ reaction rate relevant to the $$^{7}$$Be destruction in the big bang nucleosynthesis, from the $$^{7}$$Li($$p$$,$$n_{0}$$)$$^{7}$$Be reaction cross section. The decay protons from $$^{8}$$Be$$^{*}$$ to the ground and first excited states in $$^{7}$$Li were well-separately measured. The $$Gamma_{p1}/Gamma_{p0}$$ ratio of the 19.235-MeV state was deduced to be 3.4$$pm$$1.9%. The 19.86- and 20.1-MeV states were found to decay dominantly into the first excited and ground states of $$^{7}$$Li, respectively.

論文

First accurate normalization of the $$beta$$-delayed $$alpha$$ decay of $$^{16}$$N and implications for the $$^{12}$$C($$alpha$$,$$gamma$$)$$^{16}$$O astrophysical reaction rate

Kirsebom, O. S.*; Tengblad, O.*; Andreyev, A. N.; 他41名*

Physical Review Letters, 121(14), p.142701_1 - 142701_6, 2018/10

https://doi.org/10.1103/PhysRevLett.121.142701
 被引用回数：7 パーセンタイル：50.45(Physics, Multidisciplinary)

The $$^{12}$$C($$alpha$$,$$gamma$$)$$^{16}$$O reaction plays a central role in astrophysics, but its cross section at energies relevant for astrophysical applications is only poorly constrained by laboratory data. The reduced $$alpha$$ width, $$gamma_{rm 11}$$, of the bound 1$$^{-}$$ level in $$^{16}$$O is particularly important to determine the cross section. The magnitude of $$gamma_{11}$$ is determined via sub-Coulomb $$alpha$$-transfer reactions or the $$beta$$-delayed $$alpha$$ decay of $$^{16}$$N, but the latter approach is presently hampered by the lack of sufficiently precise data on the $$beta$$-decay branching ratios. Here we report improved branching ratios for the bound 1$$^{-}$$ level ($$b_{beta,11}$$) and for $$beta$$-delayed $$alpha$$ emission ($$b_{beta alpha}$$). Our value for $$b_{beta alpha}$$ is 33 $$%$$ larger than previously held, leading to a substantial increase in $$gamma_{11}$$. Our revised value for $$gamma_{11}$$ is in good agreement with the value obtained in $$alpha$$-transfer studies and the weighted average of the two gives a robust and precise determination of $$gamma_{11}$$, which provides significantly improved constraints on the $$^{12}$$C($$alpha$$,$$gamma$$)$$^{16}$$O cross section in the energy range relevant to hydro static He burning.

論文

New measurement of the $$^{8}$$Li($$alpha$$,n)$$^{11}$$B reaction in a lower-energy region below the Coulomb barrier

Das, S. K.*; 福田 共和*; 溝井 浩*; 石山 博恒*; 宮武 宇也*; 渡辺 裕*; 平山 賀一*; Jeong, S. C.*; 池添 博*; 松田 誠; et al.

Physical Review C, 95(5), p.055805_1 - 055805_4, 2017/05

https://doi.org/10.1103/PhysRevC.95.055805
 被引用回数：3 パーセンタイル：27.26(Physics, Nuclear)

The $$^{8}$$Li($$alpha$$,n)$$^{11}$$B reaction is regarded as the key reaction in the inhomogeneous big bang and in type-II supernova nucleosynthesis. Recently, the importance of this reaction to solving the $$^{7}$$Li problem, i.e., the inconsistency between the predicted and the observed primordial $$^{7}$$Li abundances, has also been noted. The most recent cross-section data published by our collaboration group in 2006 [H. Ishiyama et al., Phys. Lett. B 640, 82 (2006)] cover the 0.7- to 2.6-MeV energy region in the center-of-mass system. Here, we present additional data spanning the 0.45- to 1.80-MeV energy region. Thus, the predominant energy region for the big bang nucleosynthesis, corresponding to T$$_{9}$$ = 1 (where T$$_{9}$$ is a temperature unit equivalent to 109 K), is almost completely spanned by the previous [H. Ishiyama et al., Phys. Lett. B 640, 82 (2006)] and present results together.

論文

Cluster structures in $$^{10}$$Be from $$^{7}$$Li($$alpha$$,p)$$^{10}$$Be reaction

濱田 真悟; 安江 正治*; 久保野 茂*; 田中 雅彦*; R.J.Peterson*

Physical Review C, 49(6), p.3192 - 3199, 1994/06

https://doi.org/10.1103/PhysRevC.49.3192
 被引用回数：42 パーセンタイル：89.41(Physics, Nuclear)

65MeVの$$^{4}$$He入射粒子ビームを用いた$$^{7}$$Li($$alpha$$,p)$$^{10}$$Be反応での3核子移行反応が良い精度で行われた。ゼロレンヂDWBA近似を用いてデータとクラスターモデルの予測を較べることで、低励起のK=0$$^{+}$$,1$$^{-}$$バンドの状態への反応分光因子が求まった。Ex=17.74MeVと18.54MeVの状態に対する反応分光学因子の大きな値がみつかり、$$^{3}$$Heと$$^{7}$$Liの低エネルギーでの融合反応が宇宙初期の核合成とA=5と8の存在量の不足を説明するための重要な情報である。

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