Electron Capture and Nuclear Matrix Elements ofBe7

We calculate the ${\mathrm{Be}}^7$ electron capture rate from continuum orbits as a function of electron temperature and concentration and consider the effect on the decay rate, for some typical stellar conditions, of the statistical distribution of electrons, the electron-nucleus Coulomb interaction, relativistic and nuclear size corrections, the imperfect overlap between initial and final atomic states, and electron screening in bound decay. We also analyze the experimental information on ${\mathrm{Be}}^7$ and ${\mathrm{Li}}^7$ to obtain accurate experimental Gamow-Teller matrix elements for both the ground- and excited-state transitions and compare these matrix elements with the predictions of some simple nuclear models. This comparison supports the conclusion of other authors that near the beginning of the $1p$ nuclear shell $L-S$ coupling is better satisfied than $j-j$ coupling.