Effect of Electron-Shell Rearrangement Due toKCapture on the Intermediate-State Reorientation of Oriented Nuclei

The effect of electron-shell deexcitation following electron-capture decay on the intermediate-state reorientation of oriented nuclei is studied by considering various final electron-shell configurations of the daughter atom. It is known that these configurations are reached in a time interval much shorter than the lifetime of the intermediate state. The reorientation, affected mainly by the hyperfine interaction of the nucleus with the atomic electrons in the new configurations, is calculated using a technique previously described by Daniels and Misra. The numerical results indicate that this model is capable of explaining the observed reorientations following $K$-capture decay of ${\mathrm{Sm}}^{145}$ and ${\mathrm{Co}}^{57}$ in a double-nitrate lattice, and of ${\mathrm{Sm}}^{145}$ in a neodymium ethyl sulfate lattice.