Estimates of the 7H width and lower decay energy limit.

The 7H nucleus most likely possesses an unique decay dynamics: the four-neutron emission (or 5-body decay). We estimated theoretically the 7H width as a function of its decay energy. Uncertainty inherent to the estimated decay energy leaves a room for a possible very small width of 7H. In an attempt to observe a long living quasi stable 7H nucleus, produced in the reaction 2H(8He,7H)3He, we set an upper limit of 3nb/sr for the reaction cross section. We utilized a 20.5MeV/amu 8He beam bombarding a 5.6cm thick liquid deuterium target, and searched for 7H within 0°–50° CM angles. The obtained cross section limit corresponds to a 7H lifetime less than 1ns, which allows us to estimate a lower limit of 50–100keV for the 7H energy above the 3H+4n breakup threshold. [Copyright &y& Elsevier]