T.J. Kennett

A study of the 55Mn(n, γ)56Mn reaction

Abstract The gamma radiation from the 55 Mn(n, γ) 56 Mn reaction has been studied using a Ge(Li) spectrometer and also a Ge(Li)-NaI coincidence spectrometer. A total of 130 gamma rays were observed and their intensity and energy determined. The neutron separation energy was found to be 7272±3 keV . The level structure for the first 4000 keV is in excellent agreement with the (d, p) results. The decay modes of several of the low-energy states have been deduced from coincidence and energy information. A calculation of the correlation between the gamma-ray reduced widths and the (d, p) strength yields a coefficient of +0.84.

Large volume lithium-drifted germanium gamma-ray detectors☆

Abstract A new electroplating method was used for the fabrication of large-volume Ge(Li)-detectors in “wrap-around” configuration. The properties and performance of a 6 cm3 and a 10 cm3 detector were investigated. Some applications are described.

Study of thermal neutron capture in strontium

Abstract The 86Sr(n,γ)87Sr and 87Sr(n,γ)88Sr reactions have been studied using Ge(Li) and Ge(Li)-NaI(T1) spectrometers. Energies and intensities were determined for a total of 168γ-rays. Computer programs were coded to aid in the construction of consistent decay schemes and to search for other levels which may be populated in this reaction. By a comparison of the modes of population and de-excitation of the levels populated in both the β-decay of 88Rb and in the 87Sr(n,γ)88Sr reaction it was possible to determine the spins and parities of some of the levels in 88Sr. The neutron separation energies for 87Sr and 88Sr were measured to be 8428.2 ± 1.0 and 11113.0 ± 0.6 keV respectively.

A study of the 127I(n, γ)128I and 133Cs(n, γ)134Cs reactions

Abstract The capture γ-ray spectra of the 127 I(n, γ) 128 I and 133 Cs(n, γ) 134 Cs reactions have been investigated using a Ge(Li) spectrometer. A total of 184 high- and low-energy γ-rays were observed for the 127 I(n, γ) 128 I reaction. A neutron separation energy of 6826±3 keV was deduced by means of coincidence experiments. For the 133 Cs(n, γ) 134 Cs reaction 86 γ-rays were observed. Both spectra show an enhancement of high energy intensity which appears to be related to a high level density at low excitation energy.

A study of the 59Co(n, γ)60Co reaction

The gamma radiation from the 56Co(n, γ)60Co reaction has been studied using a Ge(Li) spectrometer. A total of 122 transitions was observed and their intensity and energy determined. The neutron separation energy of 7495±5 keV was obtained. The level structure of 60Co was determined from the primary transitions and compared to those revealed in charged particle spectra. A decay scheme has been constructed for some of the lower-lying levels. An observed dependence of partial radiative widths on the final state structure is discussed.

A study of the 75As(n, γ)76As reaction

Abstract The 75As(n, γ)76As reaction has been studied using Ge(Li) and Ge(Li)NaI(T1) spectrometers. A total of 155 gamma rays above 4 MeV and 102 gamma rays below 1 MeV were observed and their energy and intensity determined. No gamma transition from the neutron capture state to the 76As ground state was observed. In order to determine a consistent neutron separation energy it was necessary to derive a detailed decay scheme for 76As. To facilitate this derivation a coincidence experiment was also conducted. The neutron separation energy was determined to be 7329±2 keV .

The level structure of 140La and 142Pr from the (n, γ) reaction

Abstract A study of the 139 La(n, γ ) 140 La and 141 Pr(n, γ ) 142 Pr reactions using a Ge(Li) spectrometer has given neutron separation energies of 5165±5 and 5842±5 keV, respectively. Both nuclei have reasonably simple spectra for doubly-odd species due to the 83 neutron configuration. About 40 high-energy transitions were found in each case, and for 140 La the reduced dipole width to f-wave neutron states appears wider than to p-wave states. The low-energy transitions for both nuclei were also examined.

ESTIMATION OF NUCLEAR STRENGTH FUNCTIONS

Abstract A method is presented for obtaining unbiased estimates of nuclear strength functions from experimental data. The model is based on the assumption that observed reduced neutron widths have a Porter-Thomas distribution and that the level spacing are distributed according to Wigners surmise. Detailed attention is paid to estimate accuracies and a simple technique for calculating 68% confidence limits is provided. Numerical results are given for the isotopes 69, 71 Ga, 75 As, 90, 92, 94, 96 Zr and 92, 94, 96 Mo.

Study of thermal neutron capture in sulphur

Abstract The 32 S(n, γ) 33 S reaction has been studied using a Ge(Li) and a Ge(Li)NaI(TI) spectrometer. The principal aim was to establish a set of accurate energies for high-energy gamma-ray standards. In order to employ energy loops for consistency checks, a coincidence experiment was also conducted. The neutron separation energy was determined to be 8646 ± 1 keV for 33 S and 6988 ± 2 keV for 35 S and the energies of virtually all the transitions observed are accurate to 2 keV. The two parameter coincidence experiment revealed the presence of a strong 4640-2348 keV cascade belonging to the 34 S(n, γ) 35 S reaction.

On the decay of 142La

Abstract Evidence is presented that the beta transition from the 142 La ground state to the 142 Ce ground state has a unique character. On the basis of the evidence a spin and parity assignment of 2 − is made for the 142 La ground state. Angular correlation studies leading to spin assignments for four excited states in 142 Ce are also discussed. The assigments are 1.54 MeV, 2 + , 2.41 MeV, 2, 2.55 MeV, 1 and 2.71 MeV, 3 or 4.