Investigation of low-lying dipole strength in ¹²⁴Sn

Dipole excitations in the semi-magic ¹²⁴Sn nucleus were studied in (γ,γ') reactions using the γ³-high-efficiency detector setup. The experiment was carried out with quasimonoenergetic photon beams provided by the HIγS facility at the TUNL in the energy range from 5.2 to 8.6 MeV at 15 different energies. Measurements allowed to identify near 80 new transitions to the ground state, obtain reduced transition probabilities and assign parity quantum numbers to the observed excited states. Besides, the γ-γ coincidence technique gave access to the γ-decay pattern of the Pygmy Dipole Resonance, e.g. it was possible to analyse the branching ratios to the first excited 2⁺ state. Investigations were made as a part of the experimental campaign aimed to obtain a complete picture of dipole strength function evolution in Sn isotopes - from stable ¹¹²Sn to short-lived ¹³⁴Sn.