Very Neutron-Rich Very Light Nuclei

Exotic nuclei and astrophysics

“…The curve of element abundances has the maxima for silicon and iron groups, whereupon it splits into branches: one includes neutron rich isotopes and has three doubled peaks near the magic numbers of N = 50, 82, and 126, while the second includes proton-rich isotopes, which are less abundant. The production of 12 С was one of the steps of nucleosynthesis. It was shown that carbon can be produced in the reaction 4 He + 8 Be → 12 C + γ.…”

“…This reaction makes it possible to explain the existence of carbon and other observable isotopes together with it. At each nuclear fusion step initiated by explosions of the outer envelope of stars, there occurs the formation of ever heavier nuclei: 4 Не, 12 С, 16 О, 28 S, and 56 Fe. It should be recalled that production processes are accompanied by the decay of these nuclei.…”

“…In an inhomogeneous process of this kind ("big bang"), reactions like 8 Li(α, n) 11 B and 6 He(α, n) 9 Be are of crucial importance for nucleosynthesis. In simulating the hot proton-proton channel, which may occur in the explosion of supernovae, it is of interest to measure the rate of reactions like 7 Ве(p, γ) 8 В, 7 Ве(p, γ) 9 С, 8 Ве(p, γ) 9 С, and 11 С(p, γ) 12 N. Another, indirect, means for determining reaction rates and for studying nucleosynthesis consist in obtaining, by nuclear physics methods, spectroscopic data on nuclei far from the drip line. These data are used directly to describe s and r processes.…”

“…Here, experimentalists try to approach as close as possible the neutron drip line and even to study the properties of nuclei beyond it (so-called quasi-stationary states of super-neutron-rich nuclei). Attempts to discover systems consisting of neutrons exclusively (tetraneutron) or one proton and several neutrons (hydrogen-6, hydrogen-7, and so on) were continued for many years [12]. In the programs for research centers involved in the construction of new generation of accelerator facilities, including accelerators with intense beams of radioactive nuclei, the production of new exotic nuclei and investigation of their properties with an eye to simulating processes proceeding in the Universe are among the main aims.…”

Clustering and correlations at the neutron dripline

“…Very recently evidence has been presented that the ground state of 5 H exists as a relatively narrow, low-lying resonance [32]. In the case of the lightest N = 4 isotone, 4 n, nothing is known despite experimental searches over the past 40 years [33,34]. Theoretically it is difficult to produce a bound 4 neutron cluster (or "tetraneutron") [33,[35][36][37][38].…”