T.E. Ward

Decay of 53V and 57Mn

Abstract The 1.287 MeV level (J π = 7 2 − ) in 53Cr was found to be populated in the β-decay of 1.60 min 53V. Beta-gamma coincidences revealed β-rays of 2.50 and 2.20 MeV in coincidence with the 1.003 and 1.287 MeV levels in 53Cr. Four new γ-rays were found in the decay of 1.54 min 57Mn. The energy level of 1.625 MeV in 57Fe was found to be populated. Beta decay of 57Mn (J π = 5 2 − ) to the 0.014 MeV level (J π = 3 2 − ) in 57Fe was measured to be 83.5%. The beta decay Q-value of 57Mn was determined to be 2.56±0.10 MeV.

Decay of 68Cu isomers

Abstract The decay of 68 Cu was studied by means of a Ge(Li) spectrometer and scintillation detectors. Several new β- and γ-rays were observed and coincidence relations were subsequently established. Five γ-rays attributed to the isomeric decay of 68m Cu (3.8) min result from the deexcitation of an isomeric state at 721.4 keV to levels of 610.2 and 84.3 keV. The isomeric state is interpreted as a J π = 6 − state with a possible neutron-proton configuration of ( g 9 2 + ) n , ( p 3 2 − ) p . Approximately 85 % of the decay is through isomeric transitions to the 31 sec 68 Cu ( J π = 1 + ) ground state. This equilibrium activity was used to study the level stucture of 68 Zn in addition to confirming previous assignments.

Decay of 76As

Abstract The decay of 76 As was studied using a Ge(Li) spectrometer and scintillation detectors. Sixty-three γ-rays were assigned to 76 As and several coincidence measurements were performed. A decay scheme incorporating 51 of the γ-rays is tentatively proposed. From singles β-spectra and βγ coincidence measurements a β − decay Q -value of 2.99 ± 0.08 MeV was determined. Levels in 76 Se were established at energies in keV of: 559.47, 1113.92, 1216.19, 1331.64, 1689.35, 1779.76, 1788.88, 2126.63, 2430.25, 2443.70, 2454.50, 2656.72, 2670.46. Spin-parity assignments were deduced for several levels. Evidence was found for the electron-capture decay of 76 As into 76 Ge.

Decay of 63Co and 64Co

Abstract A new 0·40 ± 0·05 sec activity which was observed to have a β end point energy of 7·0 ± 0·5 MeV was assigned to 64 Co. The assignment of a 26 ± 1 sec activity with a single γ-ray of 86·3 ± 0·7 keV and a coincident β-ray of 3·6 ± 0·2 MeV was made to 63 Co.

Decay of 54V

Abstract The decay of 54V was studied with the use of a Ge(Li) spectrometer and β- and γ-scintillation detectors. Eight new γ-rays and 3 new β-rays were observed and several coincidence measurements performed. A half-life of 43 ± 3 sec was measured and a β-decay Q-value of 7.0 ± 0.1 MeV was determined. A tentative decay scheme is presented and discussed in view of the more recent theoretical and experimental studies of 54Cr.

The decay of 73Ga

Abstract The decay of 73Ga was studied with the use of a Ge(Li) spectrometer and β- and γ-ray scintillation detectors. A new γ-ray of 328 keV was found in coincidence with the previously known 740 keV γ-ray. The β branching of 73Ga to the 0·53 sec isomeric state of 73Ge was measured to have a 1·50 ± 0·10 MeV β end point with an intensity of 9 ± 1 per cent. A tentative decay scheme is presented.

Distribution of low-mass fission yields in the 14·8 MeV neutron induced fission of 238U and 232Th

Abstract The fission yields of 238U and 232Th in the mass region A=73−81 were radiochemically determined for 5 mass chains. The absolute activities for these nuclides were determined by gross beta counting and the cumulative fission yields were measured relative to 99Mo. These data were utilized to define the slope of the left wing in the light peak of the mass yield curves for 238U and 232Th. A comparison of these fission yields was made with corresponding mirror points, assuming 3·5 and 4·5 secondary neutrons emitted per fission of 238U and 232Th respectively.

Decay of152Pm isomers

Abstract Isomers of 152 Pm were observed when enriched 152 Sm was bombarded with fast neutrons. Production of the isomers was through the 152 Sm ( n, p ) 152 Pm reaction using 14·8 MeV neutrons. The β- and γ-ray decay of the isomers were studied using an 8-cm 3 Ge(Li) spectrometer and scintillation detectors. Half-lives of the ground and isomeric states were determined to be 3·8±0·5 and 7·55±0·70 min, respectively. The 3·8 min isomer was observed to decay to the ground state, first excited 2 + state, and to the β- and γ-vibrational states of 152 Sm. The 7·55 min isomeric state strongly populated a level at 1804·0 keV in 152 Sm. A spin-parity of 5 + or 6 + was deduced for the 1804·0 keV level. Tentative decay schemes for the 152 Pm isomers are proposed.

Decay of 78As

Abstract The decay of 91 min 78 As was studied using a Ge(Li) spectrometer and scintillation detectors. Fifty-four γ-rays were assigned to 78 As and several coincidence measurements were performed. A decay scheme incorporating 44 of the γ-rays is tentatively proposed. From singles β-spectra and βγ coincidence measurements, a γ-decay Q -value of 4.35±0.10 MeV was determined. Levels in 78 Se were established at energies (in keV) of: 613.7, 1308.5, 1499.2, 1502.0, 1693.4, 1721.7, 1854.0, 1997.1, 2327.6, 2508.0, 2681.2, 2798.0, 2839.2, 3144.8, 3227.1, 3232.5 and 3984.0. Spin and parity assignments were deduced for several levels.

Radioactive nucleides 79Ge and 82As

Abstract The irradiation of enriched 82 Se with 14.7 MeV neutrons was found to produce two new activities with half-lifes: 13.7±0.8 sec and 42±2 sec which were assigned to 82 As and 79 Ge, respectively. The decay characteristics of the two new nucleides were studied using a Ge(Li) spectrometer as well as with β- and γ-scintillation detectors.