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Title: 30S Studied with the 32S( p,t) 30S Reaction and the 29P( p,{gamma}) 30S Reaction Rate

Abstract

The 29P(p,gamma)30S rate affects interpretation of nova Si abundances, which have been precisely measured in presolar grains. The rate is thought to be dominated by previously unobserved 3+ and 2+ resonances above the 30S proton threshold at 4400 keV. To better understand the 29P(p,gamma)30S rate, we have studied the 30S nucleus with the 32S(p,t)30S reaction. We have observed 13 30S levels - 9 of which are above the proton threshold including a level at 4704 keV that is a candidate to be the important 3+ resonance. From the observed triton angular distributions, we additionally constrain the spins of several levels. Using our updated information, we estimate the 29P(p,gamma)30S reaction rate is approximately six times larger at nova temperatures than previously thought.

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Holifield Radioactive Ion Beam Facility
Sponsoring Org.:
USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE Office of Science (SC)
OSTI Identifier:
932058
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review C; Journal Volume: 76; Journal Issue: 4
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ANGULAR DISTRIBUTION; PROTONS; REACTION KINETICS; RESONANCE; SULFUR ISOTOPES; PHOSPHORUS 29; nova; 30s; (p; t); silicon; sulfur

Citation Formats

Bardayan, Daniel W, Blackmon, Jeff C, Fitzgerald, Ryan, Hix, William Raphael, Grzywacz-Jones, Kate L, KOZUB, RAYMOND L, Liang, J Felix, Livesay, Jake, Ma, Zhanwen, Roberts, Luke F, Smith, Michael Scott, Thomas, Jeffrey S, and Visser, Dale William. 30S Studied with the 32S(p,t)30S Reaction and the 29P(p,{gamma})30S Reaction Rate. United States: N. p., 2007. Web. doi:10.1103/PhysRevC.76.045803.
Bardayan, Daniel W, Blackmon, Jeff C, Fitzgerald, Ryan, Hix, William Raphael, Grzywacz-Jones, Kate L, KOZUB, RAYMOND L, Liang, J Felix, Livesay, Jake, Ma, Zhanwen, Roberts, Luke F, Smith, Michael Scott, Thomas, Jeffrey S, & Visser, Dale William. 30S Studied with the 32S(p,t)30S Reaction and the 29P(p,{gamma})30S Reaction Rate. United States. doi:10.1103/PhysRevC.76.045803.
Bardayan, Daniel W, Blackmon, Jeff C, Fitzgerald, Ryan, Hix, William Raphael, Grzywacz-Jones, Kate L, KOZUB, RAYMOND L, Liang, J Felix, Livesay, Jake, Ma, Zhanwen, Roberts, Luke F, Smith, Michael Scott, Thomas, Jeffrey S, and Visser, Dale William. Mon . "30S Studied with the 32S(p,t)30S Reaction and the 29P(p,{gamma})30S Reaction Rate". United States. doi:10.1103/PhysRevC.76.045803.
@article{osti_932058,
title = {30S Studied with the 32S(p,t)30S Reaction and the 29P(p,{gamma})30S Reaction Rate},
author = {Bardayan, Daniel W and Blackmon, Jeff C and Fitzgerald, Ryan and Hix, William Raphael and Grzywacz-Jones, Kate L and KOZUB, RAYMOND L and Liang, J Felix and Livesay, Jake and Ma, Zhanwen and Roberts, Luke F and Smith, Michael Scott and Thomas, Jeffrey S and Visser, Dale William},
abstractNote = {The 29P(p,gamma)30S rate affects interpretation of nova Si abundances, which have been precisely measured in presolar grains. The rate is thought to be dominated by previously unobserved 3+ and 2+ resonances above the 30S proton threshold at 4400 keV. To better understand the 29P(p,gamma)30S rate, we have studied the 30S nucleus with the 32S(p,t)30S reaction. We have observed 13 30S levels - 9 of which are above the proton threshold including a level at 4704 keV that is a candidate to be the important 3+ resonance. From the observed triton angular distributions, we additionally constrain the spins of several levels. Using our updated information, we estimate the 29P(p,gamma)30S reaction rate is approximately six times larger at nova temperatures than previously thought.},
doi = {10.1103/PhysRevC.76.045803},
journal = {Physical Review C},
number = 4,
volume = 76,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The {sup 29}P(p,{gamma}){sup 30}S reaction rate affects the interpretation of nova Si abundances, which have been precisely measured in presolar grains. The rate is thought to be dominated by previously unobserved 3{sup +} and 2{sup +} resonances above the {sup 30}S proton threshold at 4399 keV. To better understand the {sup 29}P(p,{gamma}){sup 30}S rate, we have studied the {sup 30}S nucleus with the {sup 32}S(p,t){sup 30}S reaction. We have observed 13 {sup 30}S levels, nine of which are above the proton threshold, including a level at 4704 keV that is a candidate to be the important 3{sup +} resonance. Wemore » also resolve a significant discrepancy between previously published excitation energies. From the observed triton angular distributions, we constrain the spins of several levels, ruling out several previous hypotheses and constraining some for the first time. Using our updated information, we estimate the {sup 29}P(p,{gamma}){sup 30}S reaction rate is approximately six times larger at nova temperatures than previously thought.« less
  • The structure of proton unbound {sup 30}S states is important for determining the {sup 29}P(p,{gamma}){sup 30}S reaction rate, which influences explosive hydrogen burning in classical novae and type I x-ray bursts. The reaction rate in this temperature regime had been previously predicted to be dominated by two low-lying, unobserved, J{sup {pi}=} 3{sup +} and 2{sup +} resonances above the proton threshold in {sup 30}S. To search for these levels, the structure of {sup 30}S was studied using the {sup 32}S(p,t){sup 30}S transfer reaction with a magnetic spectrograph. We have confirmed a previous detection of a state near 4700 keV, whichmore » had tentatively been assigned J{sup {pi}=}3{sup +}. We have also discovered a new state at 4814(3) keV, which is a strong candidate for the other important resonance (J{sup {pi}=}2{sup +}). The new {sup 29}P(p,{gamma}){sup 30}S reaction rate is up to 4-20 times larger than previously determined rates over the relevant temperature range. The uncertainty in the reaction rate due to uncertainties in the resonance energies has been significantly reduced.« less
  • The total neutron production cross sections for the /sup 23/Na(p,n)/sup 23/Mg, /sup 27/Al(p,n)/sup 27/Si, /sup 27/Al(..cap alpha..,n)/sup 30/P, /sup 29/Si(..cap alpha..,n)/sup 32/S, and /sup 30/Si(..cap alpha..,n)/sup 33/S reactions have been measured for bombarding energies from threshold to 6.3 MeV. The neutron detector was a 60-cm diameter sphere of polyethylene with eight /sup 10/BF/sub 3/ counters and was insensitive to the angle and energy of the emitted neutrons. Cross sections for inverse reactions have been obtained using the principle of detailed balance. The data have been used to determine parameters for statistical model calculations to facilitate extrapolation of cross sections tomore » higher bombarding energies. These reactions are relevant to problems of nucleosynthesis and stellar evolution and to studies of radiation damage. Nucleosynthesis reaction rates, N/sub A/(sigmav), were determined for the reactions studied and are tabulated for temperatures ranging from 0.4 x 10/sup 9/ to 10.0 x 10/sup 9/ K.« less
  • The {sup 30}P(p,{gamma}){sup 31}S reaction rate is expected to be the principal determinant for the endpoint of nucleosynthesis in classical novae. To date, the reaction rate has only been estimated through Hauser-Feschbach calculations and is unmeasured experimentally. This paper aims to remedy this situation. Excited states in {sup 31}S and {sup 31}P were populated in the {sup 12}C({sup 20}Ne,n) and {sup 12}C({sup 20}Ne,p) reactions, respectively, at a beam energy of 32 MeV, and their resulting {gamma}decay was detected with the Gammasphere array. Around half the relevant proton unbound states in {sup 31}S corresponding to the Gamow window for the {supmore » 30}P(p,{gamma}){sup 31}S reaction were identified. The properties of the unobserved states were inferred from mirror symmetry using our extended data on {sup 31}P. The implications of this new spectroscopic information for the {sup 30}P(p,{gamma}){sup 31}S reaction rate are considered and recommendations for future work with radioactive beams are discussed.« less