S. Monaro

Aspects of the decay of 27Mg and of 89Zr

The relative intensities of the 1.015 and 0.834 MeV gamma rays from 27Mg were determined to be (42 ± 2) : 100. The intensity of the positons from 79 hour 89Zr relative to the 0.915 MeV gamma ray, (44.5 ± 1.5 : 100), shows that ϵβ+ = 3.54 ± ± 0.14, in accord with the theoretical value. A new gamma ray of 1.75 ± 0.02 MeV was observed.

A new technetium activity: 4.5 hour 94Tcm

Abstract A 4.5 ± 0.2 hour technetium activity has been produced by bombarding molybdenum, enriched in mass 94, with 16 MeV deuterons. It decays by a 1000 ± 50 keV position branch to a level at 2440 keV in 94Mo, which then emits a cascade of 860, 710 and 870 keV gamma rays. Comparison with the decay of 52 minute 94Tc, which takes place by position emission (2.41 MeV), accompanied by gamma rays of 870, 1530, 1870, 2410, 2730 and 3200 keV, makes the assignment of the 4.5 hour activity to mass 94 unambiguous.

On the level structure of 96Mo

Abstract The level structure of 96Mo was studied through the decay of 4.3± 0.1day 96Tc and of 23.5± 0.5 hour 96Nb. Only the 770 keV transition from the first excited state and the 840 keV stop-over gamma ray from the second excited state seem to be common to these two decays. Three additional higher excited states are populated from 96Tc and four different ones from 96Nb. The various experimental results are cumulated in a tentative decay scheme, the main features being in good aggreement with those proposed in earlier studies.

Gamma radiation from the decay of the95Tc ground state and from the93Tc isomeric pair

SummaryThe γ-ray spectra, following the decay of the 20 h95Tc ground state and of the 2.7 h93Tc ground state and its 43 min isomeric state, were studied by means of scintillation techniques. The sources were produced from enriched molybdenum targets. The energies (and relative intensities in per cent per decay) of the γ-rays from (20±1) h95Tc are: (205±5) (1.0%), (680±20) (2.0%), (765±5) (82±10%), (840±10) (10.5%), (930±10) (1.7%) and (1060±10) keV (4.0%) of which the first, second and fourth have not been reported before. The decay of the (43±2) min93Tc isomer only shows γ-rays of (390±5) (I.T., 82% per decay) and (2660±40) keV (18% per decay), that of the (2.7±0.1) h ground state shows 2 new transitions of (860±20) (2.6% per decay) and (2440±30) keV (0.3% per decay) in addition to the already known ones of (1350±10) (60%), (1490±10) (30%) and (2030±30) (0.35%) keV. A slightly revised decay scheme is proposed for93Tc.RiassuntoSi è studiato, con tecniche a scintillazione lo spettro γ associato al decadimento dello stato fondamentale del95Tc (20 h) e del93Tc (stato fondamentale 2.7 h e stato isomerico 43 min). Le sorgenti radioattive sono state prodotte bombardando con deutoni molibdeno arricchito. Il decadimento del95Tc (20±1 h) è accompagnato dalle seguenti transizioni γ (intensità relativa in % di disintegrazioni): (205±5) (1.0%), (680±20) (2.0%), (765±5) (82±10%), (840±10) (10.5%), (930±10) (1.7%) e (1060±10) keV (4.0%). Soltanto la transizione isomerica di (390±5) keV (82%) e una transizione γ di (2660±40) keV (18%) seguono il decadimento dell’isomero del93Tc (43±2 min), mentre 2 nuove transizioni di (860±20) keV (2.6%) e (2440±30) keV (0.35%) sono state trovate nel decadimento del93Tc (2.7±0.1 h). Vengono proposti degli schemi di decadimento.

Levels in 150Sm from the decay of 150Eu

The decay of 14.0±0.5h150Eu to both 150Sm and 150Gd has been studied with scintillation techniques. Only one weak gamma ray of 620 keV seems to be associated with the negaton branch, but two strong gamma rays of 334 and 405 keV follow the positon and capture branch, as well as weaker gamma ray transitions of 715, 830, 920, 960, 1070, 1180, 1240, 1400, 1610 and 1920 keV. Gamma-gamma coincidences and angular correlation measurements establish the existence of a 2+ level at 334 and of a 0+ level at 739 keV. Further levels in 150Sm are at 1050, 1170, 1250, 1920 and possibly 1980 keV. The spin of the 150Eu ground state is probably 1; some speculations are made on possible proton and neutron orbital assignments.

On the decay of 105Ru

Abstract The decay of 4.4 h 105Ru was studied by means of scintillation techniques and with a double focusing spectrometer. Eight gamma rays were observed in addition to the isomeric transition from the 30 sec 105Rh daughter. This last one was shown to be of E3 character. A decay scheme is proposed which shows similarities to those of neighbouring nucleides. The strong 725 keV gamma ray does not populate the isomeric state at 129 keV, but leads directly to the 35-h ground state.