Qian, YB (reprint author), Nanjing Univ, Key Lab Modern Acoust, Nanjing 210093, Jiangsu, Peoples R China.
Recently, experimental researches on the alpha decay with long lifetime are one of hot topics in the contemporary nuclear physics [e. g. N. Kinoshita et al. (2012)  and J.W. Beeman et al. (2012) ]. In this study, we have systematically investigated the extremely long-lived alpha-decaying nuclei within ageneralized density-dependent cluster model involving the experimental nuclear charge radii. In detail, the important density distribution of daughter nuclei is deduced from the corresponding experimental charge radii, leading to an improved alpha-core potential in the quantum tunneling calculation of alpha-decay width. Besides the excellent agreement between theory and experiment, predictions on half-lives of possible candidates for natural alpha emitters are made for future experimental detections. In addition, the recently confirmed alpha-decay chain from (294)117 is well described, including the attractive long-lived alpha-decaying (270)Db, i.e., a positive step towards the "island of stability" in the superheavy mass region. (C) 2014 The Authors. Published by Elsevier B.V.