Radiative electron capture in 7Be

The continuous spectrum of photons accompanying the electron-capture transition from ⁷Be to the first excited state in ⁷Li has been measured in coincidence with the nuclear γ rays from the deexcitation of this state. The end-point energy of the photon spectrum was determined to be 388 ± 8 keV, in good agreement with accepted mass differences. The probability of $1s+2s$ radiative capture giving a photon energy greater than 50 keV per nuclear γ ray was determined to be (10.3 ± 0.6) × 10⁻⁵. This result should be compared with the value 9.2 × 10⁻⁵ predicted by the theory of Martin and Glauber. At energies higher than 120 keV the shape of the spectrum agrees with the predictions of theory. At energies lower than 120 keV the intensity falls off faster than expected from the theory. Exchange and overlap corrections to the radiative-capture theory have been calculated and shown to be too small to account for the observed discrepancy.