Isobaric-Spin Mixing inBe8States

New determination of proton spectroscopic factors and reduced widths forBe8states in the 16.5–18.0 MeV excitation energy region via the study of theLi7(Belhout1, Ouichaoui2, Beaumevieille3 et al. 2017Phys. Rev. C4000View full textAdd to dashboardCite

“…In all the measured deuteron energy spectra, the peaks associated with the two 2 + (16.626) and 2 + (16.922) states of main concern here were quite well separated due to the high energy resolution of the detection system used, with the peak for the former state being considerably more intense than the one for the latter state (see also Then, their respective wave functions can be written as (see [10])…”

“…Considering that these two 2 + states are simultaneously populated by direct and compound nucleus reaction mechanisms, we have developed formula (28) from reference [10], thus obtaining the following expression for the corresponding center of mass differential cross section. entering in it were fitted using the CERN computer program PAW [39] to reproduce the experimental deuteron energy spectra.…”

“…This information is also of great interest to nuclear astrophysics where nuclear levels of particular structure often play a prominent role in big bang and/or in stellar nucleosyntheses (BBN, SN) [6][7][8]. This is the case, for example, of the J π = 2 + , T = 1 ground states of 8 Li and 8 B nuclei and the two 2 + , T = 0 + 1 isospin-mixed states in the two α−cluster 8 Be nucleus at E x = 16.626 MeV and 16.922 MeV below the p + 7 Li threshold (E x = 17.255 MeV) [9][10][11][12][13][14][15]. In particular, the latter two loosely bound states are involved in the resonant 7 Li(p,α) 4 He hydrogen burning reaction implied both in BBN and in SN, whose cross section at stellar energies is small (σ = (4.3 ± 0.9) × 10 −5 mb at E p = 28.1 keV) and difficult to measure directly due mainly to the inhibitory effect of the p + 7 Li Coulomb barrier (B c = 2.473 MeV).…”

“…Thus, the spectroscopic information on 8 Be states in the excitation energy region, E x ∼ (16.5 − 18) MeV, is yet lacking in the literature and some nuclear reactions involving the 2 + isospin-mixed doublet have not been sufficiently explored. Especially, only few measurements have been carried out previously [10,[29][30][31] on the 7 Li( 3 He,d) 8 Be transfer reaction with cross section experimental data being reported only in reference [30]. Indeed, Marion et al [10] have measured a unique deuteron energy spectrum at a laboratory angle, θ lab = 40 • , for 3 He ion bombarding energy, E lab = 10.972 MeV, in order to determine the total widths of the 2 + (16.626) and 2 + (16.922) states of 8 Be.…”

“…[29] was limited to recording only two deuteron energy spectra at two laboratory angles, θ lab = 10 • and 25 • , for a 3 He ion bombarding energy, E lab = 15 MeV, which were used to determine level parameters for the above two 2 + states of 8 Be with pointing out their interference contributions and to search for 1p−1h states. Besides, Basak et al [30] have measured the 7 Li( − − → [9][10][11][12][28][29][30][31] and references therein), not only the corresponding spectroscopic information remains incomplete but the structures of these two special states steadily seem to be complex and not well elucidated. On the other hand concerning the reaction mechanism prevailing at thermonuclear temperatures in the 7 Li(p,α) 4 He proton capture reaction, a previous DWBA analysis [32] of precise cross section experimental data available for E p = (13 −10 3 ) keV proton energies [32,33] have led the authors to an apparently good agreement between theory and experiment, thus suggesting to interpret the data in terms of a dominant three-nucleon direct reaction transfer.…”