Ground-state properties ofH5from theHe6(d,

Abstract

We have studied the ground state of the unbound, very neutron-rich isotope of hydrogen 5 H, using the 6 He(d, 3 He) 5 H reaction in inverse kinematics at a bombarding energy of E( 6 He)=55A MeV. The present results suggest a ground-state resonance energy ER=2.4±0.3 MeV above the 3 H+2n threshold, with an intrinsic width of Γ=5.3±0.4 MeV in the 5 H system. Both the resonance energy and width are higher than those reported in some, but not all previous studies of 5 H. The previously unreported 6 He(d, t) 5 Heg.s. reaction is observed in the same measurement, providing a check on the understanding of the response of the apparatus. The data are compared to expectations from direct two-neutron and dineutron decay. The possibility of excited states of 5 H populated in this reaction is discussed using different calculations of the 6 He→ 5 H+p spectroscopic overlaps from shell-model and ab-initio nuclear-structure calculations.

Ab initio calculations of 5H resonant states

“…For completeness we have also added in Table 2, the last two experimental results from Refs. [2] and [4]. The results of [2] are fully compatible with our calculations, although, as we have already emphasized, any direct comparison between experiments and theory is not very meaningful, apart from denoting the existence of the same S-matrix pole.…”

“…[2] were confirmed by Golovkov et al [3], attributing even smaller widths to the 5 H resonant states. They are however in conflict with a recent work [4] where the resonance width was found to be much larger and comparable with the one of the 4 H ground state, although this difference could be partially attributed to the different reaction mechanism used in their production.…”

“…They are compared to previous calculations using a t-n-n 3-body model [6,10] or a microscopic RGM 3-cluster [15,20,21,19] description. The most recent experimental findings are in the last rows [2,4]. All units are in MeV.…”

“…As one can see in this figure, there is quite a large dispersion of the results, even among the microscopic approaches. The positions extracted from the experimental data [44,2,4] are indicated by filled green circles.…”

“…If there seems to be a general agreement between the experimentalist on the existence of several resonances in 5 H isotope [1,2,3,4], the parameters of these resonances vary significantly from one experiment to another. These discrepancies might be attributed to the different reaction mechanism leading to the formation of broad resonant states and to the difficulty in identifying their quantum numbers.…”