摘要
质量是原子核最基本的性质之一,核质量数据被广泛应用于核结构及核天体物理等多个研究领域.短寿命原子核质量的高精度测量是核物理研究的前沿课题.基于兰州重离子加速器装置HIRFL-CSR(cooler storage ring of heavy ion research facility in Lanzhou),我们建设了先进的等时性质谱术,精确测量了一批短寿命原子核的质量,研究了核结构及核天体物理中的前沿科学问题.本文介绍了国际研究现状,回顾了冷却储存实验环(experimental cooler storage ring,CSRe)质量测量发展过程,综述了近期取得的一些代表性成果,并对未来工作进行了展望.
As one of the most fundamental properties of nuclei,nuclear mass data are widely used in many research fields such as nuclear structure and nuclear astrophysics.At present,mass measurement of short-lived nuclei is an important research topic in nuclear physics.However,due to their small production rates and short lifetimes,it is technically challenging to measure their masses accurately.Isochronous mass spectrometry(IMS)based on the storage ring is an effective technique for measuring masses of short-lived nuclei.We established the IMS at the experimental cooler-storage ring(CSRe)in Lanzhou and developed the techniques continuously,achieving the highest precision of IMS measurement in the world.Since 2009,10 isochronous mass measurement experiments have been conducted and high-precision mass data were obtained.In the earlier researches,we focused on mass measurements for medium-mass neutron-deficient nuclei.Recently,we have extended the research to heavier and neutron-rich regions.The masses of82 Zr and84 Nb were measured for the first time,and the masses of79 Y,81 Zr,and83 Nb were re-determined with a higher precision.The results do not support the existence of the hypothetical island of pronounced lowαseparation energies for neutron-deficient Mo and Tc isotopes,making the formation of Zr-Nb cycle in the rp-process unlikely.The results also partly remove the overproduction of the pnucleus84 Sr in theνp-process simulations.The masses of the neutron-rich52–54 Sc and54,56 Ti nuclei were measured.The empirical shell gap extracted from the experimental results shows a significant subshell closure at N=32 in scandium.Combined with the theoretical calculations,it turns out that the Sc isotopes are located in the transition region of the shell evolution.Exploiting the high mass resolution of the IMS at CSRe,we also studied the nuclear isomeric states.Masses of52 g,52 mCo were measured for the first time with an accuracy of~10 ke V.Combining the results with the previousβ-γmeasurements of52 Ni,the T=2,Jπ=0+isobaric analog state(IAS)in52 Co was newly assigned,questioning the conventional identification of IASs from theβ-delayed proton emissions.Using the new results,the isobaric multiplet mass equation is restored for the masses of the T=2 multiplet.Decay of the 8+isomer in fully stripped ions94 Ru44+was directly observed by monitoring the revolution times during its circulation in the CSRe.The isomeric half-life was found to be longer by about 44%than that in the neutral atoms.A new isomer in101 In was discovered and its excitation energy was measured.Using the experimental results,the configuration-dependent shell evolution,type-II shell evolution,in odd-A nuclei is discussed for the first time.High intensity heavy-ion accelerator facility(HIAF)is a large-scale research facility for nuclear science.It is under construction and is expected to be delivered in 2025.HIAF,as the world-leading next generation heavy ion accelerator device,has the ability to generate nuclides extremely far away from the stable line and provide superior research conditions for accurately measuring masses of short-lived nuclei far away from the stable line.Based on the accumulated experience of CSR mass measurement,we will develop advanced detection devices,fully exploit the performance of HIAF,and lead the development of storage ring mass spectrometry.
作者
王猛
张玉虎
焦红扬
Meng Wang;Yuhu Zhang;Hongyang Jiao(Institute of Modern Physics,Chinese Academy of Sciences,Lanzhou 730030,China;School of Nuclear Science and Technology,University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2021年第27期3517-3526,共10页
Chinese Science Bulletin
基金
国家重点研发计划(2018YFA0404401)资助。
关键词
原子核质量
短寿命核素
等时性质谱术
壳演化
同核异能态
nuclear mass
short-lived nuclei
isochronous mass spectrometry
shell evolution
isomer state
