No abstract

13N͑p , ␥͒ 14 O is one of the key reactions which trigger the onset of the hot CNO cycle. This transition occurs when the proton capture rate on 13 N is faster, due to increasing stellar temperature ͑ജ10 8 K͒, than the 13 N ␤-decay rate. The rate of this reaction is dominated by the resonant capture through the first excited state of 14 O ͑E r = 0.528 MeV͒. However, through constructive interference, direct capture below the resonance makes a non-negligible contribution to the reaction rate. We have determined this direct contribution by measuring the asymptotic normalization coefficient for 14 O → 13 N+ p. In our experiment, an 11.8 MeV/ nucleon 13 N radioactive beam was used to study the 14 N͑ 13 N, 14 O͒ 13 C peripheral transfer reaction, and the asymptotic normalization coefficient, ͑C p 1/2 14 O ͒ 2 = 29.0± 4.3 fm −1 , was extracted from the measured cross section. The radiative capture cross section was estimated using an R-matrix approach with the measured asymptotic normalization coefficient and the latest resonance parameters. We find the S factor for 13 N͑p , ␥͒ 14 O to be larger than previous estimates. Consequently, the transition from the cold to hot CNO cycle for novae would be controlled by the slowest proton capture reaction 14 N͑p , ␥͒ 15 O.

Asymptotic forms of the scattered wave for a system of three arbitrary charged particles valid in all domains relevant to breakup are derived. The derivations are based on the relationship between the total wave function of a breakup process in a three-body system with Coulomb interactions and the wave function of the process of scattering of all three particles of the system in the continuum. The results are free from amplitude-phase ambiguity problems associated with previously known forms. A similar technique is used to obtain asymptotic forms of the three-body Coulomb Green's function.