The high-energy part of the spectrum of internal bremsstrahlung (IB) photons accompanying the allowed electron-capture (EC) transition from ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ to the ground state of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ has been measured with a Ge(Li) $\gamma$-ray spectrometer supplied with a pileup rejector. The probability for emission of internal bremsstrahlung photons with energies higher than 523.7 keV per groundstate EC decay of ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ was determined to be (9.0 ± 0.6)×${10}^{-5\mathrm{}}$. Comparable theoretical results for radiative capture of $1s+2s$ orbital electrons are 8.61 × ${10}^{-5\mathrm{}}$, deduced from the theory of Martin and Glauber, and 8.60 × ${10}^{-5\mathrm{}}$, deduced from recent improved calculations of Intemann. The confirmation of the predicted rate of radiative to ordinary $1s+2s$ capture in ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ is in good agreement with our recent similar experiment on ${}_{}{}^{51}{}_{}{}^{}\mathrm{Cr}$, but is partly at variance with previous IB $\gamma$-coincidence experiments on ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$. The transition energy of ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ was determined to be 851 ± 12 keV, in agreement with accepted atomic mass differences.

[RADIOACTIVITY ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$; measured internal bremsstrahlung, $\gamma$; deduced $I_{\mathrm{IB}}$, $Q$. Ge(Li) detector, pileup rejection, extrapolation method.]

• Received 13 July 1973

DOI:https://doi.org/10.1103/PhysRevC.8.2089