Evidence of strong dynamic core excitation in 19C resonant break-up

Abstract

The resonant breakup of 19C on protons measured at RIKEN [Y. Satou et al., Phys. Lett. B 660, 320 (2008)] is analyzed in terms of a valence-core model for 19C that includes possible core excitations. The analysis of the angular distribution of a prominent peak appearing in the relative-energy spectrum could be well described with this model and is consistent with the previous assignment of 5/2+ for this state. Inclusion of core-excitation effects are found to be essential to giving the correct magnitude of the cross section for this state. By contrast, the calculation assuming an inert 18C core is found to largely underestimate the data.