The12C+12C reaction at subcoulomb energies (I)

Abstract

The reaction 12C~-12C has been studied in the energy range Ecru=2.45-6.15 MeV by 7ray spectroscopy. Gamma-ray transitions from a large number of excited states in 2~ 23Na and 23Mg were observed, which show strong and rapid yield variations. When the influence of the Coulomb barrier is removed, these structures appear superimposed on a flat reaction yield, which does not show a strong increase at low energies, in contrast to previous work. These results obviate the need for the hypothesis of absorption under the barrier at least down to E~m=2.45 MeV. The nuclear and astrophysical aspects of the data are discussed. E Nuclear Reactions: ~2C+12C, MeV, measured as(E), Iv(O ). Deduced astrophysical S-factor. Solid state targets with low hydrogen contamination. Ge(Li) detector.

First Direct Measurement ofC12(C12Bucher1, Tang2, Fang3 et al. 2015Phys. Rev. Lett.313550View full textAdd to dashboardCite

“…With a large positive Q-value (8.99 MeV) and the relatively high natural abundance of 13 C in the target (1.1%), neutrons from 13 C( 12 C,n) 24 Mg dominate the total yield at 23 Mg S*-factor results from the present measurement (black squares) compared with previous data sets from Dayras 1977 [10] (purple circles) and Bucher 2013 [15,21] (magenta triangles). Also shown is the neutron branching ratio calculated by Dayras applied to the total 12 C+ 12 C fusion S*-factor recommended by CF88 [13] (red solid line) and the new extrapolation from this work (blue circles).…”

“…The main sources of beam-induced neutron background were from the reactions 13 C( 12 C,n) 24 Mg and, to a lesser extent, 2 H( 12 C, 13 N)n [15]. With a large positive Q-value (8.99 MeV) and the relatively high natural abundance of 13 C in the target (1.1%), neutrons from 13 C( 12 C,n) 24 Mg dominate the total yield at 23 Mg S*-factor results from the present measurement (black squares) compared with previous data sets from Dayras 1977 [10] (purple circles) and Bucher 2013 [15,21] (magenta triangles).…”

“…To estimate its contribution, the 13 C( 12 C,n) 24 Mg reaction was studied with the same setup using a 13 C beam with energies ranging between 9.5 and 5.4 MeV. Since the cross section for this reaction is much higher, relatively low beam intensities ( 50 pnA) with shorter run times were sufficient.…”

“…Since the cross section for this reaction is much higher, relatively low beam intensities ( 50 pnA) with shorter run times were sufficient. The normalized 12 C( 13 C,n) 24 Mg yield was then subtracted from the measured total neutron yield recorded with the 12 C beam [21].…”

The12C(12C,α)20Ne and12C(12C,p)23Na reactions at the Gamow peak via the Trojan Horse Method

“…Below a center of mass energy E cm of 2.5 MeV there is not enough energy to feed 23 Mg even in its ground state and α and p channel are the only relevant ones at low energies. Considerable efforts have been devoted to measure the 12 C + 12 C cross section at astrophysical energies, involving both, charged particle [11][12][13] and gamma ray spectroscopy [14][15][16][17][18][19]. Nevertheless, it has only been previously measured down to E cm = 2.5 MeV, still at the beginning of the region of astrophysical interest.…”