Radioactive silver, ${\mathrm{Ag}}^{112}$, has been produced by fast neutron bombardment of ${\mathrm{Cd}}^{112}$ and ${\mathrm{In}}^{115}$. A half-life period of 3.2 hours is observed with the upper limit of the electron beta-ray spectrum at 2.2 Mev. Gamma-rays are also emitted, the number per beta-ray is about four. The radioactive silver isomer, ${\mathrm{Ag}}^{106}$, produced by fast neutron bombardment of ${\mathrm{Ag}}^{107}$, has a positron beta-ray spectrum upper limit of 1.9 Mev and an electron beta-ray spectrum upper limit of 1.3 Mev. The half-life periods are respectively 24.5 min. and 8.2 days. The former emits no gamma-rays other than the annihilation radiation. The latter emits a complex gamma-ray spectrum. The number of gamma-rays per beta-ray is about 35. Nuclear $K$ electron capture is offered to explain this anomalously high gamma to beta ratio. A total of twenty nuclear reactions all leading to the production of radioactive silver have been observed.

• Received 17 November 1937

DOI:https://doi.org/10.1103/PhysRev.53.116