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تسجيل مستخدم جديدThe $^{8}$He and $^{10}$He spectra studied in the $(t$,$p)$ reaction
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The low-lying spectra of $^8$He and $^{10}$He nuclei were studied in the $^3$H($^6$He,$p$)$^8$He and $^3$H($^8$He,$p$)$^{10}$He transfer reactions. The $0^+$ ground state (g.s.) of $^8$He and excited states, $2^+$ at $3.6-3.9$ MeV and $(1^+)$ at $5.3-5.5$ MeV, were populated with cross sections of 200, 100-250, and 90-125 $mu$b/sr, respectively. Some evidence for $^8$He state at about 7.5 MeV is obtained. We discuss a possible nature of the near-threshold anomaly above 2.14 MeV in $^8$He and relate it to the population of a $1^-$ continuum (soft dipole excitation) with peak value at about 3 MeV. The lowest energy group of events in the $^{10}$He spectrum was observed at $sim 3$ MeV with a cross section of $sim 140$ $mu$b/sr. We argue that this result is possibly consistent with the previously reported observation of $^{10}$He, in that case providing a new g.s. position for $^{10}$He at about 3 MeV.
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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.
The two-body photodisintegration of $^4$He into a proton and a triton has been studied using the CEBAF Large-Acceptance Spectrometer (CLAS) at Jefferson Laboratory. Real photons produced with the Hall-B bremsstrahlung-tagging system in the energy ran
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oil proton and the momentum transfer. Continuum Faddeev calculations using the Argonne V18 and Bonn-B nucleon-nucleon potentials overestimate the measured cross sections by a factor 5 at low recoil proton momentum with the discrepancy becoming much smaller at higher recoil momentum.
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The cross section for the $^3$He(e, e$$d)p reaction has been measured as a function of the missing momentum $p_m$ in q$omega$ -constant kinematics at beam energies of 370 and 576 MeV for values of the three-momentum transfer $q$ of 412, 504 and 604 m
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