Systematics of the α-spectroscopic factors of the new isotope ¹⁹⁶Rn and even-even nuclei with Z = 78-90

We examined for the first time the spectroscopic factor (S_α = Γ_exp/Γ_sp) for the newly produced α-decaying neutron-deficient nucleus ¹⁹⁶Rn at the E1 room of the Ring Cyclotron Laboratory of RIKEN. In the ¹⁶⁶Er(³⁶Ar, 6n) ¹⁹⁶Rn reaction at E_lab = 208 MeV, the α-energy and the half-life of this new isotope have been determined to be 7492±30 (keV) and 3_-2⁺⁴ (ms), respectively. Including these new isotope data, we calculated the α-spectroscopic factors for the ground states of the even-even nuclei with Z = 78 - 90. We found, from the systematics of S_α-values and the largest value of the new isotope, that ¹⁹⁶Rn is more developed in α-clustering than other even-even nuclei. Moreover, the Rn isotopes were quite different from the Po isotopes in the deeply neutron-deficient region. The Rn values showed a steep increase where the node number changes from 11 to 10, presenting a contrast with the Po values. This increase may be due to the fact that the configuration of the Rn isotopes is different from that of the Po isotopes on the neutron-deficient side. Some possible explanations are discussed.