Investigation of collective and single-particle characters of excited states in 110,111Sn at HIE-ISOLDE

The experimental B(E2; 0₁⁺ → 2₁⁺) values in light even-even Sn isotopes are found to be enhanced compared to theory, a discrepancy which has eluded a satisfactory solution for over a decade. Recent Monte Carlo Shell Model (MCSM) calculations have invoked significant proton excitations from the 1g_9/2 orbital in order to explain the experimental B(E2) trend in neutron-deficient even-even Sn isotopes. To test this hypothesis, additional spectroscopic quantities such as quadrupole moments and magnetic moments are needed. In addition, the systematics of the energies and spectroscopic factors of single-particle dominated states in light odd-N Sn isotopes is needed to characterize shell evolution towards the doubly magic ¹⁰⁰Sn.

Independent campaigns of safe-energy Coulomb excitation and (d,p) reaction on neutron-deficient Sn nuclei were launched at HIE-ISOLDE, CERN. The obtained gamma-ray statistics on ¹¹⁰Sn using the Miniball spectrometer allowed the determination of the spectroscopic quadrupole moment of the 2₁⁺ state in ¹¹⁰Sn for the first time, which suggests oblate deformation of the . New and more precise B(E2) values in the same nucleus were also measured, and they are compared against MCSM and other SM results.

In a separate experiment with the ISOLDE Solenoidal Spectrometer, population of the ground state and excited states up to 4 MeV in ¹¹¹Sn from the d(¹¹⁰Sn,p)¹¹¹Sn reaction was observed.

Results from both experiments will be presented.