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Title: Low-energy proton capture reactions

Abstract

An overview of experimental problems in measuring the cross sections for (p,γ) and (p,n) reactions at low energies is given with a specific emphasis on electron screening in metallic targets. Thick target γ-ray and neutron yields are compared for Ni and NiO targets, V and VO{sub 2} targets and Mn and MnO targets. The {sup 1}H({sup 7}Li,α){sup 4}He reaction was studied in inverse kinematics with hydrogen loaded into Pd and PdAg alloy foils from gas phase. Based on these results, a new approach to electron screening in nuclear reactions is suggested.

Authors:
; ; ; ;  [1];  [2]
  1. Jozef Stefan Institute, Jamova ulica 39, Ljubljana (Slovenia)
  2. Jozef Stefan Institute, Jamova ulica 39, Ljubljana, Slovenia and Cosylab d.d., Teslova ulica 30, Ljubljana (Slovenia)
Publication Date:
OSTI Identifier:
22280377
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1595; Journal Issue: 1; Conference: 7. European summer school on experimental nuclear astrophysics, Santa Tecla, Sicily (Italy), 15-17 Sep 2013; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; CAPTURE; COMPARATIVE EVALUATIONS; CROSS SECTIONS; ELECTRONS; HELIUM 4; HYDROGEN; LITHIUM 7 TARGET; MANGANESE OXIDES; NEUTRONS; NICKEL OXIDES; NUCLEAR REACTION YIELD; PROTON REACTIONS; PROTONS; VANADIUM OXIDES

Citation Formats

Lipoglavsek, M., Cvetinovic, A., Gajevic, J., Likar, A., Vavpetic, P., and Petrovic, T. Low-energy proton capture reactions. United States: N. p., 2014. Web. doi:10.1063/1.4875299.
Lipoglavsek, M., Cvetinovic, A., Gajevic, J., Likar, A., Vavpetic, P., & Petrovic, T. Low-energy proton capture reactions. United States. doi:10.1063/1.4875299.
Lipoglavsek, M., Cvetinovic, A., Gajevic, J., Likar, A., Vavpetic, P., and Petrovic, T. Fri . "Low-energy proton capture reactions". United States. doi:10.1063/1.4875299.
@article{osti_22280377,
title = {Low-energy proton capture reactions},
author = {Lipoglavsek, M. and Cvetinovic, A. and Gajevic, J. and Likar, A. and Vavpetic, P. and Petrovic, T.},
abstractNote = {An overview of experimental problems in measuring the cross sections for (p,γ) and (p,n) reactions at low energies is given with a specific emphasis on electron screening in metallic targets. Thick target γ-ray and neutron yields are compared for Ni and NiO targets, V and VO{sub 2} targets and Mn and MnO targets. The {sup 1}H({sup 7}Li,α){sup 4}He reaction was studied in inverse kinematics with hydrogen loaded into Pd and PdAg alloy foils from gas phase. Based on these results, a new approach to electron screening in nuclear reactions is suggested.},
doi = {10.1063/1.4875299},
journal = {AIP Conference Proceedings},
number = 1,
volume = 1595,
place = {United States},
year = {Fri May 09 00:00:00 EDT 2014},
month = {Fri May 09 00:00:00 EDT 2014}
}
  • A previous study of the ground-state transition of the {sup 7}Li({ital p}{searrow},{gamma}){sup 8}Be reaction at energies of {ital E}{sub {ital p}}(lab)=80{endash}0 keV indicated the possibility of a large {ital p}-wave capture amplitude in this reaction. A similar {ital p}-wave component in the {sup 7}Be({ital p},{gamma}){sup 8}B reaction could seriously affect the extrapolation used to obtain the astrophysical {ital S} factor. The present work examines this possibility by observing the closely related {sup 7}Li({ital p}{searrow},{gamma}{sub 16.6}){sup 8}Be{asterisk} (2{sup +}, {ital T}=0+1) reaction with polarized protons at and below 80 keV. Experimental data for {sigma}({theta})/{ital A}{sub 0} and {ital A}{sub {ital y}}({theta})more » for capture to the third (16.6 MeV) excited state of {sup 8}Be are presented, and the implications discussed. {copyright} {ital 1996 The American Physical Society.}« less
  • The /sup 31/P(p, gamma )/sup 32/S reaction was studied in the proton energy range E/sub p/= 1.8 to 2.7 MeV. The decay schemes of 10 resonance levels were determined. Experimental values were obtained for the matrix elements of the dipole transitions. The levels at 10.826 MeV (E/sub p/ = 2023 keV and 10.918 MeV (E/sub p = 2118 keV were interpreted as T-mixed doublets. (2 figures, 2 tables) (tr-auth)
  • High-energy Coulomb dissociation (CD) can be used to investigate the time-reversed process, radiative capture, for unstable nuclei where the direct capture reaction is difficult or impossible to perform. At GSI, we have run a series of CD measurements involving the proton-halo nucleus {sup 8}B which plays a major role in solar-neutrino physics. We could show that for this case CD and direct proton capture yield the same result. Theoretical guidance is necessary, however, to make sure that contributions of different electro-magnetic multipolarities and nuclear dissociation processes are well under control. Recently, we have complemented the LAND/ALADIN experimental apparatus at GSImore » with new Si microstrip detectors and proton-drift-chambers to continue similar studies with radioactive beams from the fragment separator FRS at GSI. The first case of astrophysical interest to be studied will be the CD of {sup 27}P. Another case will be the 2-proton breakup of {sup 17}Ne to investigate radiative two-proton capture on {sup 15}O, a process which could modify the reaction flow of the rp-process.« less
  • We have measured the thick-target yield and analyzing power for the {sup 6}Li({ital p}{searrow},{gamma}) reaction to the ground and first excited state of {sup 7}Be below {ital E}{sub {ital p}}=80 keV. High-purity-germanium detectors were used to acquire data at five angles from {theta}=0{degree} to 124{degree}. For both states the yield, integrated from the beam energy of 80 keV down to 0 keV, is nearly isotropic and the integrated analyzing power shows only small deviations from zero. This is taken as an indication that, unlike the case of the {sup 7}Li({ital p}{searrow},{gamma}{sub 0}){sup 8}Be reaction, the {ital p}-wave-capture process is unimportantmore » compared to the {ital s}-wave process. Transition-matrix-element analyses of the ground-state data yield {ital p}-wave contributions of a few percent. Under the assumption of a constant astrophysical {ital S} factor, consistent with direct {ital s}-wave capture, a value of {ital S}=(2.69{plus_minus}0.54){times}10{sup {minus}5} MeV b has been deduced. {copyright} {ital 1996 The American Physical Society.}« less
  • A search was made for proton capture resonances in the chlorine isotopes, making use of natural and enriched targets. Eighteen resonances were observed in the proton energy region from 300 to 900 kev, and their isotopic assignment was established from a comparison of the yield curves. Single gamma- ray spectra were recorded at all resonances. The characteristic lines observed in the spectra confirmed the isotopic assignment, made from the yield curves. Gamma-ray yields are given in absolute measure. Branching ratios were measured for transitions to known Ar/sup 36/ and Ar/sup 38/ levels. (auth)