Ionization (Shakeoff) AccompanyingK-Shell Internal Conversion

Magnetic $\beta$-ray spectrometer studies at 0.05% momentum resolution with isotope-separator-prepared samples have revealed structure below the $K$ conversion lines of the 122- and 136- keV (${\mathrm{Fe}}^{57}$) and the 661-keV (${\mathrm{Ba}}^{137}$) transitions. This structure consists of an abrupt rise below the $K$ conversion line (in atomic number $Z$) at an energy displacement approximately equal to the $L_3$ binding in the ($Z+1\mathrm{}$) neutral atom, and a continuum extending to lower energies. These continua are interpreted as the spectra complementary to the (unobserved; energy near zero) $L$ -shakeoff spectra; i.e., the sum of ejected $K$- and $L$-electron energies equals a constant. The double-vacancy binding energy for $K{L}_3$ is ${7905}_{-10\mathrm{}}^{+20\mathrm{}}$ eV for Fe and 43.01±0.03 keV for Ba. The sum of $\mathrm{KL}$ shakeoff from all three $L$ subshells compared with the $K$ line is $\Sigma \frac{\mathrm{KL}}{K}=9\mathrm{}\times {10}^{-3\mathrm{}}$ for Fe and 1×${10}^{-3\mathrm{}}$ for Ba (both with uncertainties estimated at ∼50%), in good agreement with self-consistent-field overlap integrals for shakeoff in ${\beta }^{-}$ decay if one takes the effective charge change for $L$ electrons during $K$ conversion as ∼0.85 times that for ${\beta }^{-}$ decay. The spectrum shape of the $\mathrm{KL}$ continua, in the main, confirms the predictions of the nonrelativistic calculations which have been made for $\beta$-decay processes, but some discrepancies are suggested. For the less probable $K$ shakeoff accompanying $K$ conversion, preliminary values for intensities of the continua with respect to the $K$ line are $\frac{\mathrm{KK}}{K}$ between (0.4-2)×${10}^{-4\mathrm{}}$ for Fe, and $\frac{\mathrm{KK}}{K}<2\mathrm{}\times {10}^{-4\mathrm{}}$ for Ba. No $M_1$ or $M_{2,3}$ shakeoff was obvious on the $K$ line of the 14-keV transition in ${\mathrm{Fe}}^{57}$.