$Q_{\mathrm{EC}}$ value and internal bremsstrahlung spectra of ${}^{179}\mathrm{Ta}$

The total and $2p$ internal bremsstrahlung spectra accompanying the electron capture decay of ${}^{179}\mathrm{Ta}$ have been measured in singles and in coincidence with L x rays, respectively. The intensity of the total spectrum was found to be $(1.131\mathrm{}\pm 0.027)$ times that predicted by the calculations of Surić et al.; the intensity of the $2p$ spectrum was found to be $(1.097\mathrm{}\pm 0.028)$ times those calculations. The disagreement with theory is thus much smaller than the factor of 1.5–2 previously reported for ${}^{193}\mathrm{Pt}.$ The $Q_{\mathrm{EC}}$ value determined from the internal bremsstrahlung end point energy was found to be $105.61\pm 0.41$ keV. An independent value for $Q_{\mathrm{EC}}$ of $109.3\pm 3.1$ keV was determined by measuring the L to K capture ratio.