Novel evidence for the σ -bond linear-chain molecular structure in 14 C

A multi-nucleon transfer and cluster decay experiment, \begin{document}$^7$\end{document} Li( \begin{document}$^{11}$\end{document} B, \begin{document}$^{14}$\end{document} C \begin{document}$^*\rightarrow\alpha$\end{document} + \begin{document}$^{10}$\end{document} Be) \begin{document}$\alpha$\end{document} , is conducted at an incident beam energy of 55 MeV. This reaction channel has a significantly large Q-value, which favors populating the high lying resonant states in \begin{document}$^{14}$\end{document} C. The decay paths, from these resonances to various states of the final nucleus \begin{document}$^{10}$\end{document} Be, can be selected, owing to the experimentally achieved optimal resolution of the Q-value spectrum. A number of resonant states are reconstructed from the forward emitting \begin{document}$^{10}$\end{document} Be + \begin{document}$\alpha$\end{document} fragments, and their major molecular structures can be detected according to the selective decay paths and relative decay widths. A state at 22.4(2) MeV validates the previously measured and theoretically predicted band head of the positive-parity \begin{document}$\sigma$\end{document} -bond linear-chain molecular band. Two additional resonances at 22.9(2) and 24.2(2) MeV are identified and consistent with the predicted \begin{document}$2^+$\end{document} and \begin{document}$4^+$\end{document} members of the same molecular band, thus providing novel evidences for the existence of the exotic clustering chain structure in neutron-rich carbon isotopes. A few high energy resonances, which also indicate the presence of the \begin{document}$\sigma$\end{document} -bond molecular structure, are observed; however, further studies are still required to clarify their ascription in band systematics.