Search for cluster structure of excited states in 14 C

We have studied three different 2n-transfer reactions on a ¹²C target, the 2p pick-up reaction on ¹⁶O and the ⁵He transfer in the reaction ⁹Be(⁷Li,d)¹⁴C. Combined with a systematic search through experimental results for transfer reactions, inelastic excitations and other data, we have established an almost complete spectroscopy for ¹⁴C up to 18 MeV excitation. We identify states with single-particle structure that have oblate shapes and states corresponding to proton excitations that are connected to oblate (triangular) cluster states. Further we list states of prolate shape which have no simple structure related to the low-lying oblate states of ¹²C. These are proposed to have strong -clustering and to form rotational bands as a parity inversion doublet, with high moment of inertia. With these results it is possible for the first time to identify chain states expected in the isotope ¹⁴C.Received: 3 November 2003, Revised: 23 December 2003, Published online: 24 August 2004PACS: 21.10.-k Properties of nuclei; nuclear energy levels - 21.60.Gx Cluster models