ar X iv : n uc l - th / 9 80 20 51 v 1 1 7 Fe b 19 98 Non - resonant direct p - and d - wave neutron capture by 12 C
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چکیده
Non-resonant direct p-and d-wave neutron capture by 12 C Abstract Discrete γ-rays from the neutron capture state of 13 C to its low-lying bound states have been measured using pulsed neutrons at E n = 550 keV. The partial capture cross sections have been determined to be 1.7±0.5, 24.2±1.0, 2.0±0.4 and 1.0±0.4 µb for the ground (J π = 1/2 −), first (J π = 1/2 +), second (J π = 3/2 −) and third (J π = 5/2 +) excited states, respectively. From a comparison with theoretical predictions based on the non-resonant direct radiative capture mechanism, we could determine the spectroscopic factor for the J π = 1/2 + state to be 0.80 ± 0.04, free from neutron-nucleus interaction ambiguities in the continuum. In addition we have detected the contribution of the non-resonant d-wave capture component in the partial cross sections 1 for transitions leading to the J π = 1/2 − and J π = 3/2 − states. While the s-wave capture dominates at E n ≤ 100 keV, the d-wave component turns out to be very important at higher energies. From the present investigation the 12 C(n, γ) 13 C reaction rate is obtained for temperatures in the range 10 7 −
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