Positioning the neutron drip line and the r-process paths in the nuclear landscape

Abstract

Exploring nucleon drip lines and astrophysical rapid neutron capture process (r-process) paths in the nuclear landscape is extremely challenging in nuclear physics and astrophysics. While various models predict similar proton drip line, their predictions for neutron drip line and the r-process paths involving heavy neutron-rich nuclei exhibit a significant variation which hampers our accurate understanding of the r-process nucleosynthesis mechanism. Using microscopic density functional theory with a representative set of non-relativistic and relativistic interactions, we demonstrate for the first time that this variation is mainly due to the uncertainty of nuclear matter symmetry energy Esym(ρsc) at the subsaturation cross density ρsc = 0.11/0.16 × ρ0 (ρ0 is saturation density), which reflects the symmetry energy of heavy nuclei. Using the recent accurate constraint on Esym(ρsc) from the binding energy difference of heavy isotope pairs, we obtain quite precise predictions for the location of the neutron drip line, the r-process paths and the number of bound nuclei in the nuclear landscape. Our results have important implications on extrapolating the properties of unknown neutron-rich rare isotopes from the data on known nuclei. 1. Introduction.-The determination of the location of neutron and proton drip lines in the nuclear landscape is a fundamental question in nuclear physics. The drip lines tell us what is the limit of the nuclear stability against nucleon emission and how many bound nuclei can exist in the nuclear chart [1]. The quest for the neutron drip line (nDL) is also important for understanding the astrophysical rapid neutron capture process (r-process) which occurs along a path very close to the nDL in the nuclear landscape and provides a nucleosynthesis mechanism for the origin of more than half of the heavy nuclei in the Universe [2][3][4][5]. While the proton drip line (pDL) has been determined up to Protactinium (proton number Z = 91) [6], there has little experimental information on the nDL for Z > 8 [7]. Since the majority of rare isotopes inhabiting along the nDL and the r-process paths are unlikely to be observed in the terrestrial laboratory, their information has to rely on the model extrapolation based on the known nuclei, which is so far largely uncertain and hampers our accurate understanding of the r-process nucleosynthesis mechanism [8][9][10][11]. To understand and reduce the uncertainty of the model extrapolation from the known nuclei to the unknown neutron-rich rare isotopes is thus of critical importance, and we show here the symmetry energy plays a key role in this issue.

Quantified limits of the nuclear landscape

“…For such a task, the microscopic tool of choice is nuclear density functional theory (DFT) rooted in the mean-field approach [4]. During recent years, several global DFT mass tables have been calculated using different energy density functionals (EDFs): Skyrme [5][6][7], Gogny [8,9], and covariant [7,[10][11][12]. Other well-calibrated mass models include the microscopic-macroscopic finite-range droplet model (FRDM) [13] and Skyrme-HFB models based on the Hartree-Fock-Bogoliubov (HFB) method [14].…”

“…The systematic uncertainty on masses has often been estimated by an analysis of intermodel dependencies through comparing predictions of different DFT frameworks and different EDF parametrizations [5,7,15]. Statistical uncertainties are best evaluated by means of Bayesian inference methods involving full parameter estimation [16].…”

Bayesian approach to model-based extrapolation of nuclear observables

“…A microscopic approach that is well suited to providing quantified predictions throughout the nuclear chart is nuclear Density Functional Theory (DFT) [1]. An effective interaction in DFT is given by the energy density functional (EDF), whose coupling constants are adjusted to measured observables [1][2][3][4][5][6][7][8][9]. This global approach can be used to assess the uncertainties on calculated observables, both statistical and systematic [10,11].…”

“…The systematic uncertainty on separation energies is often estimated by an analysis of intermodel dependences. In the context of nuclear masses, this has been done by comparing predictions of different DFT frameworks and different EDF parametrizations [2,6,8,9].…”

A Cyclam‐Based Fluorescent Ligand as a Molecular Beacon for Cu2+ and H2S Detection

“…[22,23,25,26,[29][30][31][32][33] H 2 S is a molecule, which has recently gained renewed interest, owing to the discovery that it covers a variety of biological functions. [34][35][36] Furthermore, intracellular H 2 S le-vels, generated in response to physiological stimuli, are still controversial. [37,38] Thus, implementation of H 2 S fluorescence-based probes is still considered a very challenging task, and it has attracted much attention from several research groups in the world.…”