原子核物理评论 - The University of Liverpool Repository.DOC

NPR Paper Format—Microsoft Word Proton emission – recent results and future prospects* R.D. Page1 , D.T. Joss1 (1. Department of Physics, Oliver Lodge Laboratory, University of Liverpool, Liverpool L69 7ZE, United Kingdom ) Abstract: Considerable progress has been made in the study of proton-emitting nuclei since the first observation of direct proton emission nearly half a century ago. This has led to improvements in our understanding of this rare decay process and provided invaluable nuclear structure data far from the valley of beta stability. This paper reviews the implications of some recent results for exotic iridium, rhenium and tantalum isotopes and considers prospects for future experimental studies of proton-emitting nuclei located at and above the N=82 neutron shell closure. Key words: proton emission, alpha decay, reduced proton-decay width. CLC Number: (optional, please provide it if you know) Document code: A 1 Introduction Although proton emission is the radioactive decay mode that is expected to determine the limit of observable proton-rich nuclei for most elements, one feature of proton emitters with N ≥ 84 is that most of the proton-emitting states also have a competing ?-decay branch [1]. A typical example is 166Ir, in which proton and ?-particle emission have been observed from both the ground state and a low-lying isomeric state [2]. Measurements of the proton-decay energies, half-lives, and branching ratios indicate that the protons are emitted from ?d3/2 and ?h11/2 orbitals, respectively. As in other odd-odd nuclei in this region, in both states the odd proton is assumed to be coupled to a neutron in a ?f7/2 orbital. The unhindered ? decays from these states populate corresponding levels in 162Re which also undergo both proton and ?-particle emission. An analogous situation is observed for odd-A proton emitters in this region with the odd protons in the isomeric states occupying the ?h11/2 orbi