The unbound nucleus ${}^7\mathrm{He}$ was recently studied in the ${}^2\mathrm{H}({}^6\mathrm{He},{}^1\mathrm{H}){}^7\mathrm{He}$ reaction at 29 $A\mathrm{MeV}$ beam energy by Golovkov et al. [Phys. Rev. C 109, L061602 (2024)]. The excitation spectrum of ${}^7\mathrm{He}$ was measured up to $E_T=8$ MeV ($E_T$ is energy above the ${}^6\mathrm{He}\text{−}n$ threshold). Angular distribution for the ${}^6\mathrm{He}\text{−}n$ decay of the ${}^7\mathrm{He}3/2^{-}$ ground state can be explained by a strong spin alignment induced by a reaction mechanism. The correlation information for the higher-lying ${}^7\mathrm{He}$ excitations is available as backward-forward asymmetry for the ${}^6\mathrm{He}\text{−}n$ decay in the ${}^7\mathrm{He}$ frame. The asymmetry function has an expressed energy profile, which may be explained by using quite restrictive assumptions about structure of ${}^7\mathrm{He}$ excitations or/and peculiarities of the reaction mechanism. In the analysis of Golovkov et al. the observation the $s_{1/2}$ state in ${}^7\mathrm{He}$ is declared with $E_r\approx 2.0$ MeV. Our work is based on the same ${}^7\mathrm{He}$ data. However, the data analysis was improved and also the data interpretation is substantiated with the detailed PWBA reaction studies and coupled-channel calculations of the ${}^7\mathrm{He}$ continuous spectrum. The idea of the $s_{1/2}$ resonant state with $E_r\approx 2.0$ is rejected. In addition, the position of the $1/2^{-}$ state in ${}^7\mathrm{He}$ is confined to the interval $E_r=2.2\text{–}3.0$ MeV, with preferred value 2.6 MeV. There is indication on the second $3/2^{-}$ state in the data with $E_r\approx 4.5$ MeV and with the lower resonance energy limit $E_r\gtrsim 3.5$ MeV. Importance and prospects of more detailed correlation studies of ${}^7\mathrm{He}$ continuum are discussed.

Close

PrevNext

View figure in article

• Cluster models
• Direct reactions
• Models & methods for nuclear reactions
• Nuclear reactions
• Nuclear spin & parity
• Nuclear structure & decays
• Optical, coupled-channel & distorted wave models
• Rare & new isotopes
• 6 ≤ A ≤ 19
• Radioactive beams