Nuclear mass measurements

Abstract

Mass is a fundamental property of atomic nuclei. Nuclear masses are widely used in nuclear physics and astrophysics researches as well as nuclear technique applications. Currently it is the mass spectrometry that dominates the research field of nuclear mass measurement. Thanks to the developments of radioactive nuclear beam facilities and novel mass spectrometers, the experimental knowledge of atomic masses is rapidly expanding along two main directions, namely measurements aimed at high-precision mass values and at the most exotic nuclei far from the stability. In this article, we will review briefly the history of nuclear mass measurements and present the current status. By evaluating all available experimental data from nuclear reactions, radioactive decays and direct mass measurements, the AME (Atomic Mass Evaluation) serves the research community with the most reliable source for comprehensive information related to the nuclear masses. The latest AME was published in March, 2017 as AME2016, which will also be introduced in this article. In recent years, based on the large-scale research facility HIRFL-CSR, we have carried out precision mass measurements for short-lived nuclides by using the isochronous mass spectrometry at Institute of Modern Physics, Chinese Academy of Sciences. We achieved the highest precision of mass measurements using the Isochronous Mass Spectrometry (IMS) method and set the world record of the shortest half-life of a nuclear state whose mass has ever been measured directly. The IMS with double-time-of-flight has been established for the first time, with which the IMS experiments will be carried out in future. Masses of more than 50 short-lived nuclides have been determined with relative mass uncertainties of 10−6–10−7. The newly obtained mass values have been used to study the relevant nuclear physics and nuclear astrophysics problems. We will discuss the impact of the mass results on investigations concerning isospin symmetry in nuclides and rp nucleosynthesis process as examples.