Recent experimental studies of high-j single-particle states outside the
stable Z = 50 isotopes  and N = 82 isotones  have shown that the
centroids of single-particle strength display systematic changes with
neutron or proton number. For the case of the Z = 50 isotopes, the
separation of the h11/2 and g9/2 single-proton orbitals was found to
increase by ~2 MeV across the seven stable even isotopes. Similarly for
the N = 82 isotones, the separation of the i13/2 and h9/2 single-neutron
orbitals is seen to increase by ~0.5 MeV with proton number. These
centroid shifts are in agreement with those calculated Otsuka et al. 
with the monopole term in the tensor component of the residual
interaction between nucleons. The experiments performed to extract these
data rely on the use of single-particle transfer reactions, in
particular those well matched for high-l transfer. Over the last few
years our collaboration has made use of the facilities at Wright Nuclear
Structure Laboratory at Yale University that are particularly well
suited for these types of measurements. However, they are limited to the
stable beam / target domain, which brings our attention to the
capabilities of CARIBU  and HELIOS  at the ATLAS facility. I will
review the experimental data and present information on upcoming
experiments at ATLAS that will help us probe further the evolution of
This research was supported by the DOE Office of Nuclear Physics under Contract Nos. DE-FG02-91ER-40609 and DE-AC02-06CH11357, and the UK Science and Technology Facilities Council.
 J. P. Schiffer et al., Phys. Rev. Lett. 92, 162501 (2004).
 B. P. Kay et al., Phys. Lett. B658, 216 (2008).
 T. Otsuka et al., Phys. Rev. Lett. 95, 232502 (2005).
 A. H. Wuosmaa et al., Nucl. Instr. Meth. Phys. Res. A580, 1290 (2007).
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