Activities observed in iridium after neutron bombardment. Remarks on a paper by H. H. Hennies and A. Flammersfeld
Recently Hennies and Flanunersfeld (Naturwissenschaften, 47: 11(1960)) reported ths observation of a new 47-sec activity produced by irradiating Ir powder with slowed-down neutrons. The activity was tentatively assigned to Ir/ sup 194//sup m/. Beta activities, previously ascribed to Ir/sup 192//sup m/, were reassigned to Ir/sup 194//sup m/. A repetition of the experiment on the bombardment of Ir/sup 193/ with slow neutrons (Phys. Rev. Lettens, 3: 4S(1959)) confirmed the previous conclusions and ruled out a 47-sec period in Ir/sup 192/ or Ir/sup 19 / 4>s. It was suggested that the Hennies and Flammersfeld results may be partly ascribed to a Rh impurity and partly to the effect of fast neutrons. (J.S.R.)
Kern-Isomerie bei77Ir192 und77Ir194
Theβ- andγ-radiation of Ir192 and Ir194, produced by slow neutron irradiation, has been studied with scintillation spectrometers. A new isomeric activity with a (47±2) second-half life is found to be Ir194m, decaying by a 130 kev-transition to Ir194 and byβ-emission to excited states of Pt194. Gamma rays of energy (130±4), (323±7) and (625±20) kev were found. An upper limit for the conversion coefficient of the isomeric transition is given, which shows in connection with energy-half life-relations, that the 130 kev gamma ray is anE 3 transition.
Short-Lived Isomers of As 75 and As 77
Sources of ${\mathrm{Se}}^{75}$ and ${\mathrm{Ge}}^{77}$ have been investigated by delayed-coincidence techniques for short-lived isomeric levels in the daughter nuclei ${\mathrm{As}}^{75}$ and ${\mathrm{As}}^{77}$, respectively. The 0.305-Mev level of ${\mathrm{As}}^{75}$ has a half-life of 17 milliseconds and is depopulated by a 0.025-Mev $M2$ transition (90%) in competition with a 0.305-Mev $E3$ transition (10%). The 0.475-Mev level of ${\mathrm{As}}^{77}$ has a half-life of 116 microseconds and is depopulated by a 0.210-Mev $M2$ transition. An upper limit of 2% of the isomeric decays was placed on the intensity of any possible 0.475-Mev ground-state transition. In the beta decay of ${\mathrm{Ge}}^{77}$ to ${\mathrm{As}}^{77}$, gamma rays of the following energies were found to feed the metastable state: 0.153, 0.709, 1.08, and 1.50 Mev and probably also 0.92 and 1.96 Mev. The data obtained have been incorporated in a recently proposed decay scheme of ${\mathrm{Ge}}^{77}$. The previously discovered isomeric transition in ${\mathrm{As}}^{73}$, as well as those in ${\mathrm{As}}^{75}$ and ${\mathrm{As}}^{77}$, are probably all $M2$ transitions between $\frac{9}{2}+$ and $\frac{5}{2}\ensuremath{-}$ levels, with transition probabilities of 0.9, 1, and 0.6%, respectively, of the shell-model single proton transition probability.