The (n,α) reactions on11B,14N and16O with 14 MeV neutrons

Abstract

The angular distributions of the ~o and a I groups for the (n, ~) reactions on 11B, 14N, 160 have been measured at En=14.1 MeV. In the alB(n, %)SLi reaction the compound mechanism seems to be favoured as can be demonstrated with HauserFeshbach calculations. In the other reactions direct mechanisms dominate.

(n, ?) Reactions on light nuclei atE n =13.9 MeV

“…The angular distribution of the e o group from the reaction i 4N(n, e) iiB as presented in Figure 4a shows a strong forward peak and a slower rise at backward angles together with minima at about 60 ~ and 120 ~ and a small maximum at about 90 ~ Our measurement at E, = 13.9 MeV is in good agreement with the results at 14.1 MeV [5,7,9,10] and at 14.9 MeV [8]. The angular distribution of the a-particles leading to the first excited state of 11B (Fig.…”

“…In continuation of our previous studies of (n, c~) reactions on light nuclei, we have measured in the present experiment the reactions ~ ~N(n, e)l 1B and l~ c~)TLi at a neutron energy E, = 13.9 MeV. Up to now the reaction l*N(n, e)llB has been observed in some experiments at neutron energies near 14 MeV using cloud chambers [71, nuclear emulsions [8,9], scintillation counters [5], and counter telescopes [10,11], whereas the reaction t~ ~)TLi has been previously investigated only in one experiment at E, = 14.4 MeV [12].…”

“…There is evidence that in the reactions 9Be(n, ~)6He, lZC(n, ~)9Be, and 160(n, ~)13C the contribution from direct reaction mechanisms predominates [-2~4], whereas the reactions liB(n, c08Li and 19F(n, ~)16N proceed through compound nucleus formation [5,6]. In continuation of our previous studies of (n, c~) reactions on light nuclei, we have measured in the present experiment the reactions ~ ~N(n, e)l 1B and l~ c~)TLi at a neutron energy E, = 13.9 MeV.…”

AstrophysicalS(E) factor of8Li (?,n 0)11B and inhomogeneous Big Bang nucleosynthesis

“…6. The figure includes also the highenergy data from previous work [17][18][19] matching well with those from the present work. The energy dependence of the S(E) factor seen previously continues towards lower energies and culminates in a resonance peak at ER~0.58 MeV of width F(ER)~200keV, with S(ER) 8400 MeV b.…”

“…Previous measurements of ~aB(no, c08Li have been carried out at E.=12.5 to 20.0MeV ( [17,18] and references therein) leading to cross sections for the combined (no, C~o) and (no, el) reaction channels, which decrease smoothly from 40 to 20 mb with increasing E,. Correcting these data with the observed ratio [19] 0"34(~0)/0-34(0~1)= 1.9 (at E. = 14.1 MeV), the resulting cross sections for the liB(no, ~o)8Li reaction channel alone, 0"34(E34), were transformed into the corresponding cross sections for the 8Li(eo, no) ~'B reaction, o-12(E 12), using the principle of detailed balance, G 12 (E12) = 0.553(E34/E12) ~34 (E34).…”