Evidence for the Instability ofHe5

Nuclear structure experiments along the neutron drip line

“…The first neutron-unbound nucleus was discovered in 1937. Williams et al used the transfer reaction 7 Li(d,α) 5 He and deduced the existence of 5 He from the measured α-particle spectrum [33].…”

“…The new facilities will allow the study of neutron-unbound states along the drip line beyond oxygen. In the near future, we should be able to determine the structure of isotopes like 33 Ne, 36 Na and 39 Mg. New instruments will be matched to the new rare isotope beams and provide highly efficient and even more complete measurements than available today.…”

Observation of Ground-state Two-neutron Decay

“…The neutron energy is determined based on its time-of-flight (TOF). The TOF spectra and the position of the neutron yield the neutron's momentum vector [1]. The LISA was built and benchmarkd in 2010 and installed in the N2 vault of the NSCL in the spring of 2011.…”

“…Exploration of nuclear systems with the largest neutron excess requires the study of neutron-unbound states and nuclei. The first neutron-unbound nucleus was already discovered in 1937 by Williams, Shepperd, and Haxby who used the transfer reaction 7 Li(d,α) 5 He to deduce the existence of 5 He from the measured α-particle spectrum [1]. It took almost 30 years until the next unbound resonance was unambiguously identified with the determination of the scattering length of the dineutron system in 1965 [2].…”