The g factors of 11/2− isomers in semimagic 109Sn and 111Sn
(isomeric lifetimes τ=2.9(3) ns and τ=14.4(7) ns, respectively)
were measured by an extension of the Time Differential Perturbed Angular
Distribution technique, which uses \LaBr detectors and the hyperfine fields of
a gadolinium host to achieve precise measurements in a new regime of
short-lived isomers. The results, g(11/2−;109Sn)=−0.186(8)
and g(11/2−;111Sn)=−0.214(4), are significantly lower in
magnitude than those of the 11/2− isomers in the heavier isotopes and depart
from the value expected for a near pure neutron h11/2 configuration.
Broken-symmetry density functional theory calculations applied to the sequence
of 11/2− states reproduce the magnitude and location of this deviation. The
g(11/2−) values are affected by shape core polarization; the odd 0h11/2
neutron couples to Jπ=2+,4+,6+... configurations in the
weakly-deformed effective core, causing a decrease in the g-factor
magnitudes.Comment: 8 pages, 7 figures. Accepted in Physics Letters