Bound excited states in 27F

Abstract

The 1H(27F, 25,26,27F) reactions have been studied at 40MeV/nucleon average energy using a liquid hydrogen target. For 25F, 26F and 27F nuclei, we have observed two γ-ray peaks each originating from the decay of two bound excited states. This is the first sign of the existence of bound excited states in 26,27F. The presence of a single bound excited state in 27F is a clear indication of a substantial change in the structure of the fluorine isotopes approaching the neutron dripline. The proposed second excited states in 25,26,27F nuclei have no counterparts in either the psd or the sdpf shell model calculations suggesting the appearance of nuclear structure effects lying out of these model spaces.