The astrophysical S-factor of C-12(alpha, gamma)O-16 from the beta-delayed alpha-particle emission of N-16. Ph.D. Thesis
Thesis/Dissertation
·
OSTI ID:188482
Helium burning plays a key role in both the formation of heavy elements and the collapse of massive stars. The result of the helium burning - the C-12/O-16 ratio - determines the abundance of heavy elements and the dynamics of a massive star in its final stages before a supernova explosion. One of the two reactions in the helium burning process, the C-12(alpha, gamma)O-16 capture reaction, is poorly understood despite intense theoretical and experimental work during the last two decades. The previously extracted p-wave `S-factor` for the C-12(alpha, gamma)O-16 capture reaction at 300 keV (S(sub E1)(300)) ranges in value from 0 to 500 keV-barn. On the other hand, the beta-delayed alpha-particle emission spectrum at low energy provides a very sensitive means to determine the reduced alpha-particle width of the bound 1(-) state, hence the `S-factor`. The spectrum of low energy beta-delayed, alpha-particle emission N-16, was measured with high sensitivity; e.g., at E(sub alpha)(sup L) approximately equal to 1 MeV a sensitivity for a beta-decay branching ratio in the range of 10(exp -9) (to 10(exp -10)) was achieved. The branching ratio and spectrum of beta-decay of N-16 to the relevant broad 1(-) resonance were remeasured. The alpha-particle spectra were unfolded to remove effects of finite energy resolution (foil thickness). The authors used previous theoretical work of Ji, Filippone, Humblet, and Koonin to extract from these data the astrophysical E1 S-factor for the C-12(alpha, gamma)O-16 capture reaction and find S(sub E1)(300) = 95 +/- 6 (stat) +/- 28 (syst) keV-barn.
- Research Organization:
- Yale Univ., New Haven, CT (United States)
- OSTI ID:
- 188482
- Report Number(s):
- N--96-17335; NIPS--96-07383
- Country of Publication:
- United States
- Language:
- English
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