Novel evidence for the σ-bond linear-chain molecular structure in 14C * *Supported by the National Key research and development Program of China (2018YFA0404403), the National Natural Science Foundation of China (11875074, 11875073, 12027809, 11635015, 11961141003) and the Continuous Basic Scientific Research Project (WDJC-2019-13)

Abstract

A multi-nucleon transfer and cluster decay experiment, Li( B, C + Be) , 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 C. The decay paths, from these resonances to various states of the final nucleus 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 Be + 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 -bond linear-chain molecular band. Two additional resonances at 22.9(2) and 24.2(2) MeV are identified and consistent with the predicted and 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 -bond molecular structure, are observed; however, further studies are still required to clarify their ascription in band systematics.