Most of the heaviest nuclei synthesized in recent decades have been obtained using fusion-evaporation reactions. Due to neutron-evaporation, and the limited choice of beam-target combinations, this mechanism tends to produce mainly neutron-deficient nuclei. In addition, the cross-sections are often small, e.g 0.5 pb at most for the discovery of 294Og [1]. Multi-Nucleon Transfer (MNT) reactions are therefore expected to be a complementary mechanism to fusion-evaporation. Indeed, according to the theory [2], this mechanism is well suited to produce neutron-rich heavy ions with relatively high cross sections at forward angles of the order of µbarns.
An experiment was carried out at Argonne National Laboratory in 2023 using a 136Xe beam on a 238U target with detection of the reaction products at forward angles. The setup consisted of the Gammasphere germanium array to perform prompt γ spectroscopy, the AGFA gas-filled separator (with He gas at 4 Torr) to separate the MNT products. A decay station for decay spectroscopy studies was installed at the focal plane, consisting of a DSSD, a PPAC and silicon detectors in a tunnel configuration surrounded by four Clover germanium detectors.
The preliminary results of this analysis will be discussed in this talk.
References
[1] Yu. Ts. Oganessian, V. K. Utyonkov, Yu. V. Lobanov, F. Sh. Abdullin, A. N. Polyakov, R. N. Sagaidak, I. V. Shirokovsky, Yu. S. Tsyganov, A. A. Voinov, G. G. Gulbekian, S. L. Bogomolov, B. N. Gikal, A. N. Mezentsev, S. Iliev, V. G. Subbotin, A. M. Sukhov, K. Subotic, V. I. Zagrebaev, G. K. Vostokin, M. G. Itkis et al., Synthesis of the
isotopes of elements 118 and 116 in the 249 Cf and 245 Cm + 48 Ca fusion reactions, Phys. Rev. C 74, 044602 (2006).
[2] V.I. Zagrebaev and W. Greiner. Cross sections for the production of superheavy nuclei. Nuclear Physics A, 944:257–307, 2015. Special Issue on Superheavy Elements.
Andrea Gottardo