Beta-Spectra and Internal Conversion Coefficients for ${\mathrm{Co}}^{60}$, ${\mathrm{Nb}}^{95}$, ${\mathrm{Au}}^{198}$, and ${\mathrm{Hf}}^{181}$

Using a double-lens beta-ray spectrometer, the beta-spectra and the internal conversion coefficients for ${\mathrm{Co}}^{60}$, ${\mathrm{Nb}}^{95}$, ${\mathrm{Au}}^{198}$, and ${\mathrm{Hf}}^{181}$ were investigated. All the beta-spectra were found to be of allowed shape with end-point energies 0.306±0.005 Mev, 0.160±0.003 Mev, 0.97±0.01 Mev, and 0.408±0.008 Mev, respectively. The extra activity presented in ${\mathrm{Au}}^{198}$ was identified to be ${\mathrm{Au}}^{199}$, and the slow neutron absorption cross section of ${\mathrm{Au}}^{198}$ was estimated to be about ${10}^5$ barns.