Thresholds Observed in the C12(α,n)O15, Si28(α,n)S31, S32(α,n)Ar35, S34(α,n)Ar37, and Cl35(p,n)Ar35 Reactions

J. W. Nelson, E. B. Carter, G. E. Mitchell, and R. H. Davis
Phys. Rev. 129, 1723 – Published 15 February 1963
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Abstract

The following thresholds have been measured in the (α,n) reaction: C12 11.341±0.015; Si28 9.30±0.05, 10.55±0.05, 11.83±0.05, 12.78±0.05; S32 9.846±0.020, 10.69±0.05, 11.97±0.08; S34 5.17±0.10, 5.96±0.05, 6.90±0.05, 8.04±0.05, 9.09±0.05, 10.09±0.05, 10.31±0.05 MeV. These results are in agreement with previously published results except for the S32(α,n)Ar35 ground threshold which is 140 keV higher than expected. To confirm the value of the mass of Ar35, the Cl35(p,n)Ar35 threshold energy was measured and is 6.942±0.020 MeV. Since this result agrees with the accepted value of the Ar35 mass, the 140-keV discrepancy was not resolved. In the C12(α,n)O15 excitation curve a prominent resonance of half-width 220±60 keV was found corresponding to a level in O16 of excitation 18.10±0.06 MeV. The cross section rises to about 22 mb at the peak of this resonance. Half-life determinations yielded the values: O15 122.6±1.0, S31 2.56±0.10, and Ar35 1.76±0.03 sec.

  • Received 8 October 1962

DOI:https://doi.org/10.1103/PhysRev.129.1723

©1963 American Physical Society

Authors & Affiliations

J. W. Nelson*, E. B. Carter, G. E. Mitchell, and R. H. Davis

  • Department of Physics, Florida State University, Tallahassee, Florida

  • *Present address: Kansas State University, Manhattan, Kansas.
  • Present address: Rice University, Houston, Texas.
  • Present address: Columbia University, New York City, New York.

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Vol. 129, Iss. 4 — February 1963

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