sup 17 O( n ,. alpha. ) sup 14 C cross section from 25 meV to approximately 1 MeV

Journal Article · Sun Dec 01 04:00:00 EST 1991 · Physical Review, C (Nuclear Physics); (United States)

DOI:https://doi.org/10.1103/PhysRevC.44.2788· OSTI ID:5133879

Koehler, P E; Graff, S M ^[1]

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1. Physics Division, Group P-17, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

We have measured the {sup 17}O({ital n},{alpha}){sup 14}C cross section from thermal energy to approximately 1 MeV. A bump in the data near 3 keV could be fitted by a state whose properties are consistent with a known subthreshold {ital J} {sup {pi}}=1{sup {minus}} level at {ital E}{sub {ital x}}=8.039 MeV. The cause of the 1/{ital v} cross section near thermal energy could not be determined although the known 2{sup +} state at 8.213 MeV was found to be too narrow to contribute much to the thermal cross section. Our data are compared to measurements made via the inverse reaction. There are many differences between the two sets of data. The astrophysical reaction rate was calculated from the measured cross section. This reaction plays a role in the nucleosynthesis of heavy elements in nonstandard big-bang models. At big-bang temperatures, the experimental rate was found to be in fair agreement with the rate estimated from the previously known properties of states of {sup 18}O in this region. Furthermore, using the available information from experiments, it was estimated that the {sup 17}O({ital n},{alpha}){sup 14}C rate is approximately a factor of 10{sup 3}--10{sup 4} times larger than the {sup 17}O({ital n},{gamma}){sup 18}O rate at big-bang temperatures. As a result, there may be significant cycling between {sup 14}C and {sup 17}O resulting in a reduction of heavy-element nucleosynthesis.

• OSTI ID: 5133879
• Journal Information: Physical Review, C (Nuclear Physics); (United States), Journal Name: Physical Review, C (Nuclear Physics); (United States) Vol. 44:6; ISSN 0556-2813; ISSN PRVCA
• Country of Publication: United States
• Language: English

Related Subjects

663430* -- Nucleon-Induced Reactions & Scattering-- (1992-)
663520 -- Nuclear Mass Ranges-- A=6-19-- (1992-)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BARYON REACTIONS
COSMOLOGY
CROSS SECTIONS
DIRECT REACTIONS
ENERGY RANGE
EV RANGE
HADRON REACTIONS
KEV RANGE
MILLI EV RANGE
MULTI-NUCLEON TRANSFER REACTIONS
NEUTRON REACTIONS
NUCLEAR REACTIONS
NUCLEON REACTIONS
NUCLEOSYNTHESIS
OXYGEN 17 TARGET
SYNTHESIS
TARGETS
THREE-NUCLEON TRANSFER REACTIONS
TRANSFER REACTIONS