Mechanism of neutron production in supernova explosions.

Abstract

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Mechanism of neutron production in supernova explosions. Cameron, A. G. W. Abstract If the main energy source giving rise to the exponential tails in the light curves of Type I supernovae is the spontaneous fission of Cf254, then nuclei of medium atomic weight in these stars must have captured an average of 200 or more neutrons. It has been suggested that in the imploding envelopes of these stars hydrogen is exhausted by (p, ~) reactions, the resulting positron emitters decay in a few seconds, and (a, n) reactions produce neutrons from certain resulting nuclei. It has also been suggested that heavy nuclei keep capturing these neutrons until the neutron binding energy falls so low that (n, ~) and (~, n) reactions have equal rates, the nuclei then waiting until beta decay ocCurs. Recent computations by the writer show that typical nuclei at such "waiting points" have capture cross sections about 10-2 times the cross sections for (n, p) reactions on light proton capture products unstable to positron em~ss~on. Protons emitted by the latter reactions cannot be produced in appreciable quantity by this general scheme unless positron decay daughters are also almost always neutron producers and unless such neutron producers are regenerated many times. Until recently it appeared that a cycle of reactions involving C'2, N'3, and C'3 nuclei would meet this requirement, but a recent cross section measurement at Oak Ridge has eliminated this possibility, and no other possibility appears to be plausible. It is therefore concluded that the most likely neutron source is an envelope layer in which a small amount of hydrogen has mixed with C12 produced in the core and has been exhausted (producing C'3) before the explosion. The amount of Cf254 synthesized should be sensitive to the initial ratio of hydrogen to carbon abundances. Measurements of the fractional light output in the exponential tails of several Type I supernovae would, therefore, be very valuable. Atomic Energy of Canada Ltd. Ontario, Canada Publication: The Astronomical Journal Pub Date: February 1958 DOI: 10.1086/107682 Bibcode: 1958AJ.....63...48C full text sources ADS |