K.S. Krane

Neutron Capture by 94,96Zr and the Decays of 97Zr and 97Nb

Cross sections for radiative neutron capture have been determined for (94)Zr and (96)Zr using the activation technique with samples of naturally occurring Zr metal. The sensitivity to the correction for epithermal neutrons in the determination of small thermal cross sections is discussed, particularly in view of the variation in the resonance integral at different sites in the reactor. Gamma-ray spectroscopic studies of the decays of (97)Zr and its daughter (97)Nb have been performed, leading to improved values of the energies and intensities of the emitted γ rays, and correspondingly improved values for the energy levels and β feedings of excited states populated in (97)Nb and (97)Mo.

The decays of 70,72Ga to levels of 70,72Ge and the neutron capture cross sections of 69,71Ga

The decays of 21-min (70)Ga and 14-h (72)Ga have been studied from neutron-irradiated Ga. Several discrepancies in previous studies are resolved and inconsistencies in the previous (72)Ge data set are addressed. New values are proposed for the energies and β-decay branchings of the (72)Ge levels. Energies and intensities of the (70)Ga γ rays are also discussed. A new measurement and critical discussion of the (72)Ga half-life is offered. Measurements of the (69)Ga and (71)Ga thermal neutron capture cross sections and resonance integrals are also reported.

Gamma-ray spectroscopy in the decay of 83Se to levels of 83Br

High-resolution γ ray spectroscopy experiments have been done to study the emissions from the radioactive decay of 22-min (83g)Se produced from neutron capture using samples of enriched (82)Se. Energy and intensity values have been obtained to roughly an order of magnitude greater precision than in previous studies. Based on energy sums, 2 new levels are proposed in the daughter (83)Br and one previously proposed level is shown to be doubtful. Some 25 new transitions appear to decay with the (83)Se halflife, about half of which can be accommodated among the previous or newly proposed levels. Several previous γ ray placements are shown to be inconsistent with the new determinations of the (83)Br energy levels, but cannot be accommodated anywhere else among the known levels. As a result of the missing γ ray placements, some of the β branchings in the decay to levels of (83)Br appear to be negative. Gamma rays from the 2.4-h decay of the daughter (83)Br to levels of (83)Kr have also been observed, along with decays of (81g)(,m)Se present as a small impurity in the enriched samples and also as a strong component in irradiated samples of natural Se.

The decay of 194Au to levels in 194Pt

High-resolution gamma-ray spectroscopy measurements of the energies and intensities of the γ rays emitted in the decay of (194)Au (produced following the decay of 447-y (194)Hg) have been made with increased precision relative to previous studies, leading to correspondingly improved values for β-decay branching intensities and energy levels in the daughter (194)Pt. Numerous newly observed transitions are reported, and two possible new levels in (194)Pt are suggested.

Neutron capture cross sections of 70Zn and the decay of 71mZn

Radiative neutron capture was studied in the 70Zn(n,γ)71m,gZn reaction in order to determine the thermal neutron capture cross sections for the reactions. The resonance integrals were also measured to facilitate corrections for the epithermal neutron component. In addition, cross sections for the 64Zn(n,γ)65Zn and 68Zn(n,γ)69mZn reactions were determined. Through high-resolution γ-ray spectrometry in the 71mZn decay, a new set of γ-ray energies and intensities was obtained of roughly an order of magnitude greater precision than the previous set, and several transitions new to the decay scheme are proposed. The implications for the properties of the levels of 71Ga are discussed. More precise values of the decay half-lives for 69mZn, 71gZn, and 71mZn have been determined.

Neutron capture cross sections of 194Hg and the decays of 195Hg

The thermal cross section and resonance integral have been determined for radiative neutron capture by radioactive (194)Hg by observing the γ rays emitted in the decay of (195)Hg. Captures leading to the low-spin isomer of (195)Hg give σ=877 b and I=10,270 b, while captures leading to the high-spin isomer give σ=49 b and I=608 b. Energies and intensities of the γ rays emitted in the decays of (195)Hg produced by neutron capture have been obtained with increased precision relative to previous studies with sources produced by other reactions, leading to correspondingly improved values for β-decay branching intensities and energy levels in (195)Au. New values for the half-lives of (195g)Hg and (195m)Hg are also reported.

The decays of 109,111Pd and 111Ag following neutron capture by Pd

Improved precisions of the energies and intensities of the γ rays emitted in the decays of (109)Pd and (111g,m)Pd have been obtained based on a high-resolution spectroscopic study of these γ emissions from radioactive samples produced by neutron capture by natural Pd. Correspondingly improved values of the energies and β feedings of the levels in the (109,)(111)Ag daughters have been deduced. More precise energies and intensities have also been determined for the γ rays emitted in the decays of the (111)Pd daughter activities (111g,m)Ag to (111)Cd.

The decays of 117Cd following neutron activation of enriched 116Cd

A new set of spectrometric data on γ ray energies and intensities in the decays of the 117g.mCd isomers (2.5h and 3.4h) has been accumulated. Uncertainties in the energies and intensities have been reduced by about an order of magnitude relative to previous studies. Through observation of their time dependence, several transitions are shown as incorrectly assigned in previous studies, and many new transitions were assigned to the respective decays. The placements of other transitions are shown to be doubtful based on poor energy fits. Energies and β-decay intensities have been deduced for the excited states in the 117In daughter. Some additional γ rays from the decay of daughter 117gIn to 117Sn have also been observed.

Gamma-ray spectrometry in the decay of (194)Ir to (194)Pt.

As a complement to a resent high-resolution spectrometric investigation of the decay of (194)Au to levels of (194)Pt, a similar study has been undertaken of the decay of 19-h (194)Ir to (194)Pt. The two decays populate a similar set of levels in (194)Pt, and so the complementary investigations with similar resolution and efficiency permit a direct comparison of the two data sets. Overall there is excellent agreement between the energies of the common γ-ray transitions and also between the deduced energies of the excited states in (194)Pt. The (194)Ir half-life has been remeasured to be 19.20(2)h.

Gamma-ray energies in the decay of 38Cl.

In order to resolve a long-standing discrepancy of some 30 standard deviations between the two most precise previously reported values of the γ-ray energies in the (38)Cl decays, we have undertaken a new precision measurement of the decay energies using a variety of different sources for energy calibration. The deduced energies from the present work are 1642.668 ± 0.010 and 2167.395 ± 0.010 keV. These results agree very well with one of the previous reports and disagree with the other.