Nuclear levels near thresholds

R-matrix analysis of theβdecays ofN12Hyldegaard1, Alcorta2, Bastin3 et al. 2010Phys. Rev. C627410View full textAdd to dashboardCite

“…The only feature of the spectra that is reproduced is the narrow Hoyle peak just above threshold. The small increase in the calculated spectrum just above the peak (the "ghost" of the Hoyle state [27]) is similar in shape to the measured spectrum in this energy region, which explains part of the structure. Looking at the value of χ 2 /df = 281 in Table I, it is much larger than unity, as expected.…”

“…Taking the 8 Be ground state as an example, the peak area can be calculated to 0.57π using the narrow state approximation, but this is not the full integral of ρ j b because the high-energy tail or "ghost" [27] of the state contributes at higher energy (see Fig. 3), giving a total integral of π .…”

The 1·67 MeV Level in 9Be

“…As shown by Barker and Treacy (1962) the energy dependence of the cross section for the 9Be(p, p')9Be* process leading to the 1·67 Me V level of 9Be may be written as (1) where C is a normalization constant; Pp(E) and Pn(E) are penetration factors for the outgoing proton and for the neutron in the subsequent decay of the 9Be* nucleus, of channel energy E above the 8Be+n threshold; and the constants Er and y2 are the resonance energy and the reduced width of the 1·67 Me V level, of spin and parity t+ (Lauritsen and Ajzenberg-Selove 1966).…”

“…Arguments are given below to justify the exclusion of more complicated possibilities. correspond to values of E r• )12 for fits by Barker and Fitzpatrick (1968) and Barker and Treacy (1962) respectively to other data as described in the text.…”

“…These properties have prompted suggestions, such as that of Spencer, Phillips, and Young (1960), that it is "not a state in the usual sense". Barker and Treacy (1962) showed that a straightforward description of this level is possible in terms of R·matrix theory (Lane and Thomas 1958). In their analyses they assumed a channel radius of 4·35 fm (as with all analyses to be discussed here) and a reduced width y2 of 1·01 MeV, as estimated by Barker (1961) from a weak· coupling shell model.…”