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

Abstract

We examined for the first time the spectroscopic factor (Sα = Γexp/Γsp) 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 Elab = 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 Sα-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.