Radioactive Isotopes of Palladium and Silver from Palladium

The bombardment of palladium with 6.3 Mev deuterons yields radioactive periods of 17 min. and 13 hr. (both negative) in palladium and periods of 26 min. (positive) and 180 hours (negative) in silver. The palladium activities are due to neutron capture and are probably attributable to ${\mathrm{Pd}}^{111}$, and ${\mathrm{Pd}}^{109}$, respectively. Fast neutron bombardment of silver shows that there are undoubtedly two distinct long-period negative activities of about 180 hours half-life in the silver due to ${\mathrm{Ag}}^{106}$ and ${\mathrm{Ag}}^{111}$. The positive 26 min. silver activity is also associated with ${\mathrm{Ag}}^{106}$, being an example of the existence of isomeric isotopes. The active ${\mathrm{Ag}}^{111}$ can be formed from ${\mathrm{Pd}}^{110}$ directly by proton capture and indirectly by a chain reaction through ${\mathrm{Pd}}^{111}$. The two 180-hour silver activities differ in that there is a strong gamma-radiation accompanying the beta-emission from ${\mathrm{Ag}}^{106}$ and little or no gamma-radiation from ${\mathrm{Ag}}^{111}$. The upper limits of energy for the beta-spectra of the 26-min. (${\mathrm{Ag}}^{106}$), 13-hr. (${\mathrm{Pd}}^{109}$), and 180-hr. (${\mathrm{Ag}}^{111}$) activities are 2.24 Mev, 1.08 Mev, and 0.80 Mev, respectively. The excitation functions for the 13-hr. (${\mathrm{Pd}}^{109}$) and 180-hr. (${\mathrm{Ag}}^{111}$) activities are determined by bombarding a stack of 25 palladium foils. These results are compared, since the processes involved correspond to the escape of a neutron or a proton from similar excited nuclei.