合成和发现超铀化学元素、探索超重核稳定岛

Search for and synthesis of transuranium elements, and exploration of the stability island of superheavy nuclides

合成新元素拓展元素周期表、探索原子核存在极限是核物理前沿研究领域。相关研究工作涉及的重大物理问题有:存在多少种化学元素?超重元素具有什么样的化学性质?超重元素化学性质是否符合元素周期律的外推预期?最大的核幻数是什么?是否存在稳定的或长寿命的超重核素?在极强库仑场中原子核具有哪些奇特的结构和性质?等等。经过逾半个世纪的不懈努力,元素合成取得了巨大成就,已将周期表从92号扩展至118号元素,完成了周期表上第七周期元素填充。文章回顾了在自然界寻找超重元素的历程,评述了利用人工核反应合成超铀元素和探索理论预言的超重核稳定岛的进展、成果、现状以及目前面临的困难,展望了未来的研究工作,简介了基于国家重大科技基础设施--强流重离子加速器装置开展超重研究的计划。

The exploration of the limit to the existence of nuclides in terms of proton and mass numbers, naturally related to the synthesis of new chemical elements, is a foremost subject of nuclear physics. The synthesis of new elements and exploration of the stability island of superheavy nuclides predicted a long time ago have stimulated extensive research both experimentally and theoretically. The overarching important topics include: How many chemical elements can exist? What are the chemical properties of superheavy elements? Up to which element is the ordering scheme of Mendeleev's periodic table still valid? What are the maximum proton and neutron magic numbers? Are there stable or long-lived superheavy nuclides? What exotic structures and properties of superheavy nuclides appear under extremely strong Coulomb fields? And so forth. Over the last half century, momentous achievements in the synthesis of transuranium nuclides and elements have been made. To date, superheavy elements with atomic number up to 118 and hundreds of superheavy nuclides have been discovered in various laboratories,resulting in the completion of the seventh period of the periodic table of elements. This paper reviews the search for superheavy elements in nature and the artificial synthesis of transuranium nuclides and elements using nuclear reactions induced by high neutron flux and energic heavy ions, and presents a perspective on the field of superheavy nuclide studies, with an emphasis on the High Intensity Heavy-ion Accelerator Facility of the Major National Science and Technology Infrastructure Facilities Program in China.