α decay of the new isotope 204Ac
Min Huang, Z.G. Gan, Zheng Zhang, Long Ma, J.G. Wang, Muyang Zhang, H. B. Yang, Chen Yang, Xinnan Huang, Z. Zhao, S. Y. Xu, L.X. Chen, Xianfei Wen, Y. Niu, Cenxi Yuan, Y. L. Tian, Yuqi Wang, J.Y. Wang, M.L. Liu, Y. H. Qiang, W. Q. Yang, H.B. Zhang, Zitong Lu, Shu Qing Guo, Wenxue Huang, Yan He, Z. Z. Ren, Shan-Gui Zhou, X. H. Zhou, Honglin Xu, V. K. Utyonkov, A. A. Voinov, Yu. S. Tsyganov, А. N. Polyakov
Abstract
A new proton-unbound isotope 204Ac was produced in the fusion-evaporation reaction Tm(40169Ca,5n)204Ac and identified via the recoil-α correlation at the gas-filled recoiled separators SHANS2 and SHANS. The excitation function for producing 204Ac was measured and the optimal beam energy was evaluated to be 212 MeV. Nineteen ER - α1 - α2 - α3 decay chains were observed for this isotope. Based on these chains, the α-particle energy and half-life of 204Ac were determined to be 7948(15) keV and 7.4−1.4+2.2 ms, respectively. Both are consistent with the theoretical prediction. The reduced α-decay width was deduced to be 49−15+10 keV, which indicates a favored α decay for 204Ac. In addition, more precise decay properties of Eα = 7883(15) keV and T1/2 = 7.7−1.6+2.7 ms were obtained for 205Ac.