Estimates of the 7H width and lower decay energy limit

The H-7 nucleus most likely possesses an unique decay dynamics: the four-neutron emission (or 5-body decay). We estimated theoretically the H-7 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 H-7. In an attempt to observe a long living quasi stable H-7 nucleus, produced in the reaction H-2(He-8,H-7)He-3, we set an upper limit of 3 nb/sr for the reaction cross section. We utilized a 20.5 MeV/amu He-8 beam bombarding a 5.6 cm thick liquid deuterium target, and searched for H-7 within 0degrees-50degrees CM angles. The obtained cross section limit corresponds to a H-7 lifetime less than 1 ns, which allows us to estimate a lower limit of 50-100 keV for the H-7 energy above the H-3 + 4n break-up threshold. (C) 2004 Published by Elsevier B.V.