Shape polarization in the tin isotopes near N=60 from precision g-factor measurements on short-lived 11/2- isomers

The g factors of 11/2(-) isomers in semimagic Sn-109 and Sn-111 (isomeric lifetimes tau = 2.9(3) ns and tau = 14.4(7) ns, respectively) were measured by an extension of the Time Differential Perturbed Angular Distribution technique, which uses LaBr3 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(-); Sn-109) =-0.186(8) and g(11/2(-); Sn-111) =-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 h(11/2) 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 0h(11/2) neutron couples to J(pi) = 2(+), 4(+), 6(+)... configurations in the weakly-deformed effective core, causing a decrease in the..-factor magnitudes.

Automated summary

The g factors of 11/2(-) isomers in semimagic Sn-109 and Sn-111 were measured and found to be significantly lower than those of heavier isotopes, indicating a deviation from the theoretical expectation.