Search forH7inH2+

Abstract

An experimental search for the low-lying 7 H resonance was performed with the 2 H( 8 He, 3 He) 7 H reaction studied at forward center-of-mass angles (6 • -14 • ) with a 42 A MeV 8 He beam. No well-pronounced peak of 7 H was observed; however, the obtained spectrum was found to have a peculiarity at ∼2 MeV above the t + 4n threshold. The data allow us to set a c.m.s. cross section level of ∼30 µb/sr for the low-energy part of the 7 H spectrum. The test reaction 2 H( 12 Be, 3 He) 11 Li, involving the same one-proton (d, 3 He) transfer, was studied simultaneously on a 71 A MeV satellite beam where a cross section of 1 mb/sr was measured for the population of the 11 Li ground state.

Two-neutron radioactivity and four-nucleon emission from exotic nuclei

“…2(c [24]. This limit is based, however, on the production cross-section estimate, which we can find too optimistic nowadays [23]. Thus, an extreme long-lived g.s.…”

Observation of the $^7$H excited state

“…[1] for the specific task of searching for extreme low-lying (and therefore long- * Electronic address: chudoba@jinr.ru living) 7 H g.s. Together with theoretical estimates for the lifetimes in the five-body decays, this allowed to establish the lower decay-energy limit E T > 50 − 100 keV for 7 H. The decay energy E T and missing mass (MM) mean the same value having zero value at the 3 H+4n decay threshold. The observation of a quite low-lying 7 H resonance state with E T ∼ 0.57 MeV produced in the 12 C( 8 He, 7 H) 13 N reaction was declared in Ref.…”

“…decays via unique five-body 3 H+4n decay channel. This form of nuclear dynamics has not yet been studied at all, and it was discussed that in 7 H this decay mechnism may lead to such an exclusive phenomenon as 4n radioactivity [1,2]. Unfortunately, there is no definite reliable information about such an interesting system.…”

“…The search for 7 H has a long, but not fortunate history. It was searched but not found among the nuclear-stable products of ternary fission of 252 Cf [3] and in pion double charge-exchange 7 Li(π − ,π + ) reaction [4].…”

“…The search for 7 H has a long, but not fortunate history. It was searched but not found among the nuclear-stable products of ternary fission of 252 Cf [3] and in pion double charge-exchange 7 Li(π − ,π + ) reaction [4]. Since the emergence of the radioactive ion beams (RIB), the evident way to search for 7 H is proton removal from 8 He.…”