Structure ofHe7by proton removal fromLi8with the

Abstract

We report on a study of the structure of the unbound nucleus 7 He utilizing the proton-removal reaction 2 H( 8 Li, 3 He) 7 He. Combining the present results with those of our prior measurements of the neutron-adding reaction 2 H( 6 He, p) 7 He, a consistent picture emerges for the low-lying excitations in 7 He. Specifically, the negative-parity sequence of resonances, in order of excitation energies, is consistent with 3/2 − , 1/2 − , and 5/2 − . The stable-beam reactions 2 H( 7 Li, t) 6 Li and 2 H( 7 Li, 3 He) 6 He were also measured. The results are compared with the predictions of nuclear structure models, including those of ab initio quantum Monte Carlo calculations.

Spectroscopy ofHe7using theBe9(HeRenzi1, Raabe2, Randisi3 et al. 2016Phys. Rev. C5010View full textAdd to dashboardCite

“…In the present work, we calculated a SF = 0.608 (18), in agreement with the values from the neutron knock-out experiment [9] and with the SF from an R-matrix analysis of 7 Li(d, 2 He) 7 He reaction data [45]. A smaller SF has been extracted from the angular distribution study in the proton removal and neutron pickup reactions [11,12]. Although it should be noted that the spectroscopic factors are model-dependent and not pure observables [47], our result is in line with the theoretical prediction in Table I.…”

“…Three other experiments showed a resonance with an excitation energy in good agreement with Ref. [13]: the 9 Be( 15 N , 17 F) 7 He transfer reaction [3], 8 He(p,d) 7 He at 15.6 MeV/nucleon [6] and (d, 3 He) reaction with 8 Li beam of 76 MeV [12]. In the latter two measurements the decay of the 7 He 5/2 − state into α + 3n was also confirmed.…”

“…Wuosmaa et al [11,12] used complementary reactions, 8 Li(d, 3 He) and 6 He(d,p), to selectively populate and probe states with different configurations, 5/2 − and 1/2 − , respectively. The (d,p) reaction data suggested a resonance at 2.6 MeV with a FWHM ∼ 2 MeV (see Fig.…”

“…The solid lines represent the energy of the states in 7 He, the shaded bands correspond to the widths (Refs. [11,12] from the position and energy of coincident α particles, the reaction 9 Be + 6 He → X + 8 Be → X + α + α is reconstructed with the resonant particle spectroscopy technique [32]. Then, the center-of-mass energy of the undetected system X is obtained.…”

“…[4], replacing the carbon target by a liquid-hydrogen target; the low-lying resonance was not confirmed. Furthermore, no evidence for a state below 1 MeV has been found in five other experiments [5,11,12,14,15] using a variety of techniques. These studies have provided positive signs of a first-excited state at higher energy, although these observations are not completely in agreement among themselves, as shown in Fig.…”