Unambiguous Identification of the Second 2+ State in 12C and the Structure of the Hoyle State
Unambiguous Identification of the Second 2+ State in 12C and the Structure of the Hoyle State
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DOI：
10.1103/physrevlett.110.152502
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发表时间：
2013-04-10
影响因子：
8.6
通讯作者：
Wu, Y. K.
中科院分区：
文献类型：
--
作者：
Zimmerman, W. R.;Ahmed, M. W.;Wu, Y. K.
C-12的第二个J(pi) = 2（+）态，在50多年前被预测为霍伊尔态的激发态，已经通过C-12(γ, α (0))Be-8反应明确地确定了。利用光学时间投影室对C-12光分解产生的α粒子进行了检测。在高能伽玛S装置中，利用强近单能伽玛射线束在9.1 - 10.7 MeV的束流能量范围内收集数据。测量的角分布确定了截面和E1-E2相对相作为能量的函数，从而明确地确定了C-12中的第二2（+）态在10.03(11)MeV，总宽度为800(130)keV，基态γ衰变宽度为60(10)MeV；B (E2: 2 (2) (+) - > 0 (1) (+)) = 0.73 (13) e(2)调频(4)或0.45 (8)W.u。。对于试图揭示C-12中三个α粒子态性质的模型来说，比基态扩展更广的Hoyle态及其旋转2（+）态是一个挑战和约束。具体来说，它挑战了从头算晶格有效场论计算，预测基态和霍伊尔态的均方根半径相似。DOI: 10.1103 / PhysRevLett.110.152502
The second J(pi) = 2(+) state of C-12, predicted over 50 years ago as an excitation of the Hoyle state, has been unambiguously identified using the C-12(gamma, alpha(0))Be-8 reaction. The alpha particles produced by the photodisintegration of C-12 were detected using an optical time projection chamber. Data were collected at beam energies between 9.1 and 10.7 MeV using the intense nearly monoenergetic gamma-ray beams at the HI gamma S facility. The measured angular distributions determine the cross section and the E1-E2 relative phases as a function of energy leading to an unambiguous identification of the second 2(+) state in C-12 at 10.03(11) MeV, with a total width of 800(130) keV and a ground state gamma-decay width of 60(10) meV; B(E2 : 2(2)(+) -> 0(1)(+)) = 0.73(13)e(2) fm(4) [or 0.45(8) W.u.]. The Hoyle state and its rotational 2(+) state that are more extended than the ground state of C-12 presents a challenge and constraints for models attempting to reveal the nature of three alpha-particle states in C-12. Specifically, it challenges the ab initio lattice effective field theory calculations that predict similar rms radii for the ground state and the Hoyle state. DOI: 10.1103/PhysRevLett.110.152502