The Radiations ofTantalum182,Rhenium186,188, andGold199

A survey of the radiations of ${\mathrm{Ta}}^{182}$, ${\mathrm{Re}}^{186,188}$ and ${\mathrm{Au}}^{199}$ has been made down to energies of the order of 5 kev with a small 180 degree spectrometer. The disintegration scheme of ${\mathrm{Ta}}^{182}$ is complex. The twenty or more conversion lines found superimposed on the beta-ray spectrum and the numerous peaks found in the photoelectron spectrum are analysed into seventeen gammas in the energy region 80 to 330 kev. In addition, three gamma-rays of energies 1.13, 1.22, and 1.24 Mev are found. The continuous spectrum has an end point at 0.53 Mev. The radiations of ${\mathrm{Re}}^{186}$ consist of a single beta-ray group of maximum energy 1.07 Mev and two gamma-rays of energies 0.138 and 0.212 Mev. The 0.138 Mev gamma-ray is converted. Coincidence experiments strongly suggest that the mode of decay is one involving the emission of a single beta-ray group, followed by the cascade emission of the two gamma-rays. The disintegration of ${\mathrm{Re}}^{188}$ is more complicated. A single group of beta-rays is found with the end point at 2.10 Mev. Five gamma-rays with energies essentially the same as those reported by Miller and Curtiss are present. All the radiations of ${\mathrm{Au}}^{199}$ lie below 0.32 Mev. Superimposed on the beta-ray spectrum are eight conversion lines that may be attributed to 4 gamma-rays having energies of 0.024, 0.051, 0.156 and 0.207 Mev. The beta-rays have a maximum energy of 0.32 Mev. A possible decay scheme is suggested.