Pairing-quadrupole interplay in the neutron-deficient tin nuclei: First lifetime measurements of low-lying states in ^106,108Sn

Abstract

The lifetimes of the low-lying excited states $2^{+}$ and $4^{+}$ have been directly measured in the neutron-deficient ^106,108Sn isotopes. The nuclei were populated via a deep-inelastic reaction and the lifetime measurement was performed employing a differential plunger device. The emitted γ rays were detected by the AGATA array, while the reaction products were uniquely identified by the VAMOS++ magnetic spectrometer. Large-Scale Shell-Model calculations with realistic forces indicate that, independently of the pairing content of the interaction, the quadrupole force is dominant in the $B(E2;2_1^{+}\to 0_{g.s.}^{+})$ values and it describes well the experimental pattern for ^104−114Sn; the $B(E2;4_1^{+}\to 2_1^{+})$ values, measured here for the first time, depend critically on a delicate pairing-quadrupole balance, disclosed by the very precise results in ¹⁰⁸Sn.