title: Equilateral-triangular shape in 14C.
abstract: An equilateral-triangular shape of three alpha clusters surrounded by excess neutrons is suggested for 14C, based on the molecular-orbit model. It is found that the attractive interaction between an excess neutron and an alpha particle stabilizes the K(pi)=0(+) and 3(-) rotational bands, which demonstrates an equilateral-triangular symmetry. This K(pi)=3(-) band at 3 MeV below the 10Be+alpha threshold energy corresponds to the experimentally observed band built on top of the second 3(-) state. A positive-parity rotational band (0(+), 2(+), 4(+)) arises similarly. These two bands suggest a molecular 3-alpha structure stabilized by the excess neutrons and can be viewed as a realization of the alpha crystallization in the dilute nuclear medium.
authors.affiliation: Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033, Japan. itagaki@phys.s.u-tokyo.ac.jp
authors.forename: N
authors.initials: N
authors.lastname: Itagaki
authors.forename: T
authors.initials: T
authors.lastname: Otsuka
authors.forename: K
authors.initials: K
authors.lastname: Ikeda
authors.forename: S
authors.initials: S
authors.lastname: Okabe