2025/03/22 by Khirk, M., Grigorenko, L. V., Nikolskii, E. Yu. +1
#FOS: Physical sciences #Nuclear Experiment (nucl-ex) #Nuclear Theory (nucl-th)
paper · doi:10.48550/arxiv.2503.17859
The unbound nucleus 7He was recently studied in the 2H(6He,1H)7He reaction at 29 A MeV beam energy in Ref.[M.S. Golovkov et al., Phys. Rev. C 109, L061602 (2024)]. The excitation spectrum of 7He was measured up to ET=8 MeV (ET is energy above the 6He-n threshold). Angular distribution for the 6He-n decay of the 7He 3/2- ground state can be explained by a strong spin alignment induced by a reaction mechanism. The correlation information for the higher-lying 7He excitations is available as backward-forward asymmetry for the 6He-n decay in the 7He frame. The asymmetry function has an expressed energy profile which may be explained by using quite restrictive assumptions about structure of 7He excitations or/and peculiarities of the reaction mechanism. In the analysis of [M.S. Golovkov et al., Phys. Rev. C 109, L061602 (2024)] the observation the s1/2 state in 7He is declared with Er ≈ 2.0 MeV. Our work is based on the same 7He 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 7He continuous spectrum. The idea of the s1/2 resonant state with Er ≈ 2.0 is rejected. In addition, the position of the 1/2- state in 7He is confined to the interval Er=2.2-3.0 MeV, with ``preferred'' value 2.6 MeV. There is indication on the second 3/2- state in the data with Er ∼ 4.5 MeV and with the lower resonance energy limit Er \gtrsim 3.5 MeV. Importance and prospects of more detailed correlation studies of 7He continuum are discussed.