Question

Question #1 2- Why the resonance in the reaction 1"C(p.n)"N higher than the corresponding resonance in the 1N (n,p) 1"C

Answer 1

Answer:

The ¹⁴N(n,p)¹⁴C reaction plays an important role in the s process of nucleosynthesis: 14N is very abundant since it is a dominant product of hydrogen-burning in the CNO cycle, the stage prior to the s process. So with its relatively high cross-section, this reaction can act as a strong neutron poison in the reaction chain to heavier elements.

The present result confirms that the 14N(n, p)14C reaction is a strong neutron poison in the s process of stellar nucleosynthesis.

Data obtained as a result of investigations of the (n,p) and (p, n) reactions may be very important for a better understanding of many scenarios of nucleosynthesis. The recent experimental results presented below, apply to the processes of explosive nucleosynthesis and the s-process. So, depending on the 14N(n,p)14C reaction cross-section, 14N may act as a strong neutron "poison" during the chain of reactions involving the 14C(p,n)14N neutron source in the s-process.

N:B:

33. 14N(n, p)14C Qm = 0.6259 The po angular distribution has been measured at En = 14 MeV: see (1981 AJ01). At En = 60 MeV the stongest transitions are to 14C*(7.0 + 8.3, 11.3, 15.4) and to the giant resonanace peak, centered at 20.4 MeV, and angular distributions have been studied to these groups: see (1986AJ01). For cross sections of astrophysical interest see 15N. A study of P-odd and left-right asymmetries with polarized thermal neutrons is reported by (1988AN19). See also (1986BOIK, 1988ELIC; applied).

39. 14C(@Li, “He)14N Qm = -3.350 Angular distributions have been studied at E(Li) = 34 and 62 MeV (see (1986AJ01)], at 93 MeV (1986BR33, 1987DE02, 1988DE47, 1989DE34; to 14N*(0, 3.95)) and at 84, 150 and 210 MeV (1987W109, 1986AN29, 1988AN06; to 14N*(0, 2.31, 3.95)). 14N*(3.95) dominates the spectra: see e.g. (1987W109). 14N*(5.11, 5.83, 6.20, 7.03, 8.49) are also populated (1980WH03, 1987W109). For studies of the GT strength see (1980WH03, 1987W109). See also (1987AU04, 1988AUIE, 1988GAIN, 1989AU1B) and (1986AJ01).