Resonance States of Hydrogen Nuclei ⁴H and ⁵H Obtained in Transfer Reactions with Exotic Beams

To investigate ⁵H resonance states with a better instrumental resolution, we utilized the two-neutron transfer reaction ³H(t, p)⁵H accomplished with the use of a cryogenic liquid-tritium target and 57.5-MeV triton beam. As a result of this study, a valuable fraction of protons detected at θ_lab = 18°-32° in ptn coincidence events was attributed to the states of the ⁵H nucleus. Two resonance states situated at 1.8 plusmn; 0.1 and 2.7 ± 0.1 MeV above the t + n + n decay threshold were obtained in the missing mass energy spectrum of the ⁵H nucleus. The peak located close to E_5H = 1.8 MeV was clearly seen in the ^H spectrum obtained from the energy distributions of ³H nuclei emitted in the reaction ²H(⁶He, ⁵H)³He at θ _lab = 17°-32°. The width (Γ_obs ≤ 0.5 MeV) obtained for the two ⁵H resonance states is surprisingly small. A state of ⁴H with E_res = 3.3 MeV and γ² = 2.3 MeV was obtained in the reaction ²H(t, p)⁴H from the spectra of protons leaving the target at θ_lab = 18°-32° and detected in coincidence with neutrons emitted in the decay of ⁴H nuclei.