Collectivity of the 2p-2h proton intruder band of $^{116}$Sn

International audience; The half-life of the 42+ state of the 2p-2h proton intruder band of Sn116 has been measured with the fast-timing technique. The lifetime of T1/2=29(10) ps leads to a transition probability BE2;42+→22+=40(13) Weisskopf units, which is in very good agreement with the large BE2;22+→03+ value measured previously and provides strong support for the 03+ state as the bandhead of the intruder configuration and for the shape coexistence in the semimagic Sn116 nucleus. IBM-2 calculations with mixing reproduce the experimental data very well, giving insight into the degree of mixing between the different states.