Resonant states in \(^{7}\)H. I. Experimental studies of the \(^2\)H(\(^8\)He,\(^3\)He) reaction

• Published in: arXiv.org 2021-01
• Main Authors: Muzalevskii, I A, Bezbakh, A A, E Yu Nikolskii, Chudoba, V, Krupko, S A, Belogurov, S G, Biare, D, Fomichev, A S, Gazeeva, E M, Gorshkov, A V, Grigorenko, L V, Kaminski, G, Kiselev, O, Kostyleva, D A, M Yu Kozlov, Mauyey, B, Mukha, I, Parfenova, Yu L, Piatek, W, Quynh, A M, Schetinin, V N, Serikov, A, Sidorchuk, S I, Sharov, P G, Shulgina, N B, Slepnev, R S, Stepantsov, S V, Swiercz, A, Szymkiewicz, P, Ter-Akopian, G M, Wolski, R, Zalewski, B, Zhukov, M V
• Format: Article
• Language: English
• Subjects: Angular momentum; Excitation; Experiments; Missing mass (astrophysics)
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2010.09655

The extremely neutron-rich system \(^{7}\)H was studied in the direct \(^2\)H(\(^8\)He,\(^3\)He)\(^7\)H transfer reaction with a 26 AMeV secondary \(^{8}\)He beam [Bezbakh et al., Phys. Rev. Lett. 124 (2020) 022502]. The missing mass spectrum and center-of-mass (c.m.) angular distributions of \(^{7}\)H, as well as the momentum distribution of the \(^{3}\)H fragment in the \(^{7}\)H frame, were constructed. In addition to the investigation reported in Ref. [Bezbakh et al., Phys. Rev. Lett. 124 (2020) 022502], we carried out another experiment with the same beam but a modified setup, which was cross-checked by the study of the \(^2\)H(\(^{10}\)Be,\(^3\)He\()^{9}\)Li reaction. A solid experimental evidence is provided that two resonant states of \(^{7}\)H are located in its spectrum at 2.2(5) and 5.5(3) MeV relative to the \(^3\)H+4\(n\) decay threshold. Also, there are indications that the resonant states at 7.5(3) and 11.0(3) MeV are present in the measured \(^{7}\)H spectrum. Based on the energy and angular distributions, obtained for the studied \(^2\)H(\(^8\)He,\(^3\)He)\(^7\)H reaction, the weakly populated 2.2(5) MeV peak is ascribed to the \(^7\)H ground state. It is highly plausible that the firmly ascertained 5.5(3) MeV state is the \(5/2^+\) member of the \(^7\)H excitation \(5/2^+\)-\(3/2^+\) doublet, built on the \(2^+\) configuration of valence neutrons. The supposed 7.5 MeV state can be another member of this doublet, which could not be resolved in Ref. [Bezbakh et al., Phys. Rev. Lett. 124 (2020) 022502]. Consequently, the two doublet members appeared in the spectrum of \(^{7}\)H in [Bezbakh et al., Phys. Rev. Lett. 124 (2020) 022502] as a single broad 6.5 MeV peak.