New Binding Energy for the Two-Neutron Halo ofLi11

Abstract

The extended radius of a halo nuclide is very sensitive to the minute binding energy of its valence nucleons. The binding energy of 11Li has been measured with high precision by using the radio-frequency spectrometer MISTRAL at CERN's ISOLDE facility. The new two-neutron separation energy of 378+/-5 keV is 25% higher than the previously accepted value with an uncertainty 5 times smaller.

Active targets for the study of nuclei far from stability

“…The derived 11 Li two-neutron separation energy is S 2n = 363 (22) keV. This value is in good agreement with values from the MISTRAL transmission spectrometer [46] and the TITAN penning trap measurement [47] of S 2n = 378(5) keV and S 2n = 369.15(65) keV respectively. These measurements were significantly different from the Atomic mass evaluation at this time [48] of 299.6(19.4) keV.…”

Reaction mechanism of two–neutron transfer in DWBA

“…In this nucleus, the last two neutrons are very weakly bound (S 2n ≈ 380keV [6], [11], [16]). If one neutron is taken away from 11 Li, a second neutron will come out immediately leaving behind the core of the system, the ordinary nucleus 9 Li.…”

Magnetic resonance and radio frequency mass spectrometers and their application

“…There were reports of repeated measurements and refinements of the masses of the short-lived neutron-rich sodium isotopes 26−30 Na [44,45] and the masses of the exotic magnesium isotopes 20−33 Mg [45,46]. In one of the more recent studies [47] the French scientists applied the radio-frequency mass spectrometer MISTRAL to precision measurements of the mass of the short-lived radioactive isotope 11 Li (T 1/2 ∼ 8 ms), thus making it possible to determine the binding energy of excess neutrons in this exotic nucleus, a point of particular importance for the theory of strong interactions.…”