The open question of where, when, and how the heavy elements beyond iron enrich our Universe has triggered a new era in nuclear physics studies. Of all the relevant nuclear physics inputs, the mass of very neutron-ric...The open question of where, when, and how the heavy elements beyond iron enrich our Universe has triggered a new era in nuclear physics studies. Of all the relevant nuclear physics inputs, the mass of very neutron-rich nuclides is a key quantity for revealing the origin of heavy elements beyond iron. Although the precise determination of this property is a great challenge, enormous progress has been made in recent decades, and it has contributed significantly to both nuclear structure and astrophysical nucleosynthesis studies. In this review, we first survey our present knowledge of the nuclear mass surface, emphasizing the importance of nuclear mass precision in r-process calculations. We then discuss recent progress in various methods of nuclear mass measurement with a few selected examples. For each method, we focus on recent breakthroughs and discuss possible ways of improving the weighing of r-process nuclides.展开更多
The steady equilibrium conditions for a mixed gas of neutrons, protons, electrons, positrons and radiation fields （abbreviated as npe^± gas） with or without external neutrino flux are investigated, and a genera...The steady equilibrium conditions for a mixed gas of neutrons, protons, electrons, positrons and radiation fields （abbreviated as npe^± gas） with or without external neutrino flux are investigated, and a general chemical potential equilibrium equation μn = μp ＋ Cμe is obtained to describe the steady equilibrium at high temperatures （T 〉 10^9 K）. An analytic fitting formula of coefficient C is presented for the sake of simplicity, when neutrinos and antineutrinos are transparent. It is a simple method to estimate the electron fraction for the steady equilibrium npe^± gas that adopts the corresponding equilibrium condition. As an example, we apply this method to the GRB accretion disk and confirm that the composition in the inner region is approximately in equilibrium when the accretion rate is low. For the case with external neutrino flux, we calculate the initial electron fraction of neutrino-driven wind from the proto-neutron star model M15-l1-r1. The results show that the improved equilibrium condition makes the electron fraction decrease significantly more than the case μn = μp ＋ μe when the time is less than 5s post bounce, which may be useful for r-process nucleosynthesis models.展开更多
文摘The open question of where, when, and how the heavy elements beyond iron enrich our Universe has triggered a new era in nuclear physics studies. Of all the relevant nuclear physics inputs, the mass of very neutron-rich nuclides is a key quantity for revealing the origin of heavy elements beyond iron. Although the precise determination of this property is a great challenge, enormous progress has been made in recent decades, and it has contributed significantly to both nuclear structure and astrophysical nucleosynthesis studies. In this review, we first survey our present knowledge of the nuclear mass surface, emphasizing the importance of nuclear mass precision in r-process calculations. We then discuss recent progress in various methods of nuclear mass measurement with a few selected examples. For each method, we focus on recent breakthroughs and discuss possible ways of improving the weighing of r-process nuclides.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10733010, 10673010 and 10573016)the National Basic Research Program of China (2009CB824800)+2 种基金the Scientific Research Funds of Sichuan Provincial Education Department (10ZC014, 2009ZB087)China West Normal University(09A004)Graduate Innovation Funds of USTC
文摘The steady equilibrium conditions for a mixed gas of neutrons, protons, electrons, positrons and radiation fields （abbreviated as npe^± gas） with or without external neutrino flux are investigated, and a general chemical potential equilibrium equation μn = μp ＋ Cμe is obtained to describe the steady equilibrium at high temperatures （T 〉 10^9 K）. An analytic fitting formula of coefficient C is presented for the sake of simplicity, when neutrinos and antineutrinos are transparent. It is a simple method to estimate the electron fraction for the steady equilibrium npe^± gas that adopts the corresponding equilibrium condition. As an example, we apply this method to the GRB accretion disk and confirm that the composition in the inner region is approximately in equilibrium when the accretion rate is low. For the case with external neutrino flux, we calculate the initial electron fraction of neutrino-driven wind from the proto-neutron star model M15-l1-r1. The results show that the improved equilibrium condition makes the electron fraction decrease significantly more than the case μn = μp ＋ μe when the time is less than 5s post bounce, which may be useful for r-process nucleosynthesis models.
