Lifetime of the First Excited State of B11

F. R. Metzger, C. P. Swann, and V. K. Rasmussen
Phys. Rev. 110, 906 – Published 15 May 1958
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Abstract

Using the reaction B11(p, p)B11* as the source of Doppler-broadened 2.14-Mev gamma radiation, resonance fluorescence from the first excited state of B11 has been observed. For a bombarding energy of 3.0 Mev and a thick target of B4C, the shape of the cone containing gamma rays capable of exciting the 2.14-Mev level was determined. It agrees with the expectation based on the known excitation curve and the kinematics of the B11(p, p) reaction assuming an isotropic distribution of the B11* recoils. From the experimental resonance scattering cross section a mean life of 4.8×1015 second was calculated for the first excited state of B11, assuming the spin of this level to be ½. A self-absorption experiment yielded τγ=4.3×1015 second when a value of 1250° was used for the Debye temperature of B4C. A final value of (4.7±0.6)×1015 second was adopted for the mean life of the 2.14-Mev first excited state of B11. This value of the lifetime further strengthens the argument for spin ½, but it does not allow any conclusion about the M1 or E1 character of the gamma-ray transition and thus about the parity of the 2.14-Mev level.

  • Received 17 January 1958

DOI:https://doi.org/10.1103/PhysRev.110.906

©1958 American Physical Society

Authors & Affiliations

F. R. Metzger, C. P. Swann, and V. K. Rasmussen

  • Bartol Research Foundation of the Franklin Institute, Swarthmore, Pennsylvania

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Issue

Vol. 110, Iss. 4 — May 1958

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