One-particle excitations outside the 54Ti semi-magic core: The 55V and 55Ti yrast structures

The level structures of 55V and 55Ti, the two nuclei with a single nucleon outside the semi-magic 5422Ti32 core, have been investigated in order to provide new tests of full pf-shell calculations with the GXPF1A interaction. The addition of a proton does not appear to affect the N = 32 shell gap significantly, although comparisons between calculations and experiment at high spins (Iπ ≥ 21 / 2-) indicate the need for a larger model space for an accurate description of the data in this regime. The energy separation between the ν p1 / 2 and ν f5 / 2 orbitals in neutron-rich Ti isotopes is not large enough to result in an N = 34 shell gap. However, comparisons between the 55Ti data and the calculations argue for the presence of a sizable N = 34 gap in 54Ca.