$\mathrm{\Delta }v=2$ seniority changing transitions in yrast $3^{-}$ states and B(E3) systematics of Sn isotopes

We show for the first time that the generalized seniority scheme explains reasonably well the $B(E3)$ systematics for the $(0^{+}\to 3_1^{-})$ transitions in the Sn-isotopes, which are odd-tensor $E3$ transitions connecting different seniority states ($\mathrm{\Delta }v=2$). Additionally, we also present Large Scale Shell Model (LSSM) calculations to support our interpretation. The generalized seniority scheme points to the octupole character of these $3^{-}$ states in Sn isotopes.