The radioactivity induced in platinum by 5 MV deuterons is composite in character. Chemical separations of the active elements together with an analysis of the decay curves establish that at least two radioactive isotopes each of iridium and platinum are formed. The decay periods of the former are about 28 min. and 8.5 hrs. while the latter have periods in the neighborhood of 49 min. and 14.5 hrs. Inasmuch as the platinum activity emits both positrons and electrons it seems reasonable to ascribe the activities to the isotopes ${\mathrm{Pt}}^{193}$ and ${\mathrm{Pt}}^{197}$ resulting from neutron capture. The active iridium isotopes are probably formed in reactions involving deuteron capture and alpha-particle emission, and the likely radioactive isotopes are ${\mathrm{Ir}}^{194}$ and ${\mathrm{Ir}}^{196}$. The transmutation functions for the reactions leading to iridium isotopes exhibit maxima indicative of resonance penetration of the platinum nucleus by the deuteron; the nature of the transmutation functions for the reactions giving platinum isotopes is not made certain by these experiments, because of the relative weakness of the platinum activities.

• Received 7 April 1936

DOI:https://doi.org/10.1103/PhysRev.49.788