Spectroscopy ofHe7using theBe9(He

Abstract

The unbound nucleus 7 He has been investigated via the reaction of a 16.8 MeV 6 He radioactive ion beam on a 9 Be target. The measurement of the outgoing 8 Be through its well characterized two-α decay permitted the energy of the 6 He +n system to be reconstructed. Through comparison with a complete Monte Carlo simulation incorporating R-matrix lineshapes, the 7 He ground state was determined to lie 0.380(28) MeV above the neutron decay with a width of = 0.179(21) MeV. A neutron spectroscopic factor SF = 0.608(18) was extracted in agreement with the most recent calculations. Significant evidence was found for a broad resonance lying at 2.6(2) MeV above threshold with a FWHM = 2.3(3) MeV. These parameters are fully consistent with the properties of 1/2 − state reported by Wuosmaa et al. [Phys. Rev. C 72, 061301(R) (2005)]. Limits were also put on the presence of narrow resonances seen in earlier experiments.

Recent Progress in Gamow Shell Model Calculations of Drip Line Nuclei

“…A clear consequence of the strong intertwinings of the continuum degrees of freedom and internucleon correlations at drip lines consists of the odd-even staggering found in the helium chain [9,10]. Indeed, odd helium isotopes (except 3 He) are all resonances and bear widths of several hundreds of keV [10][11][12]. Conversely, the even-even helium isotopes 4,6,8 He are bound, with 6,8 He both exhibiting halo properties [13][14][15].…”