A Precise Measurement of the Energy Change in the Transmutation of Beryllium into Lithium by Proton Bombardment
1938; American Institute of Physics; Volume: 54; Issue: 3 Linguagem: Inglês
10.1103/physrev.54.171
ISSN1536-6065
AutoresSamuel K. Allison, Lester S. Skaggs, Nicholas M. Smith,
Tópico(s)Chemical Synthesis and Characterization
ResumoThe very high yield of alpha-particles from the reaction $_{4}\mathrm{Be}^{9}(p, \ensuremath{\alpha})_{3}\mathrm{Li}^{6}$ has made it possible to measure their energies by deviating a beam through 90\ifmmode^\circ\else\textdegree\fi{} in an electrostatic field. A steady source of high voltage, which could be measured to 0.1 percent up to 40,000 volts, was used to deflect the alpha-particles. Two experiments are reported in which the beryllium was bombarded by 320 kv and 383 kv protons, respectively. The energy distribution curves of the alphas show a sharp high energy limit, and this limit increases with bombarding energy of the protons. The experiment shows that the energy balance of the reaction is 2.152\ifmmode\pm\else\textpm\fi{}0.04 Mev, corresponding to 2.310\ifmmode\pm\else\textpm\fi{}0.04\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}3}$ atomic weight unit. This establishes the diffference in mass between ${\mathrm{Be}}^{9}$ and ${\mathrm{Li}}^{6}$ as 2.99804\ifmmode\pm\else\textpm\fi{}0.00009. If we assume that of the two, the mass of ${\mathrm{Li}}^{6}$ is more accurately known, and adopt Livingston and Bethe's value of 6.01686\ifmmode\pm\else\textpm\fi{}0.00020, the experiment shows that the mass of ${\mathrm{Be}}^{9}$ is 9.01491\ifmmode\pm\else\textpm\fi{}0.00025.
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