Observation of the Exotic <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msubsup><mml:mrow><mml:mn>0</mml:mn></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:mrow></mml:math> Cluster State in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>He</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>8</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>
Z. Yang, Y L Ye, Bo Zhou, H. Baba, R J Chen, Yufeng Ge, B. S. Hu, H. Hua, D. Jiang, M. Kimura, C. Li, K A Li, J G Li, Q. T. Li, X Q Li, Z H Li, J. L. Lou, M. Nishimura, H. Otsu, D. Y. Pang, Wei-Liang Pu, Rui Qiao, S. Sakaguchi, H. Sakuraï, Y. Satou, Y. Togano, K. Tshoo, H. Wang, S. Wang, Kang Wei, Jun Xiao, F. R. Xu, X. F. Yang, K. Yoneda, Hao-Song You, Tianle Zheng
Abstract
We report here the first observation of the 0_{2}^{+} state of ^{8}He, which has been predicted to feature the condensatelike α+^{2}n+^{2}n cluster structure. We show that this state is characterized by a spin parity of 0^{+}, a large isoscalar monopole transition strength, and the emission of a strongly correlated neutron pair, in line with theoretical predictions. Our finding is further supported by the state-of-the-art microscopic α+4n model calculations. The present results may lead to new insights into clustering in neutron-rich nuclear systems and the pair correlation and condensation in quantum many-body systems under strong interactions.