Towards lifetime measurement of excited states in 120Sn using thermal neutron capture

The intruder bands in Sn isotopes, based on the 2p-2h excitation across the $Z=50$ proton shell gap, are well-known to exhibit shape coexistence near the neutron mid-shell region. The spectroscopic signatures are enhanced E0 transitions between the $0^{+}$ band heads and enhanced E2 transitions within rotational bands built on these $0^{+}$ band heads. However, lifetime information for the excited $0^{+}$ states is incomplete. Experimental details for the neutron-capture reaction and analysis procedures are described, and the first result of the $2_1^{+}$ lifetime demonstrates proper calibration of the setup.