W.V. Prestwich

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.

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.

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.

Level scheme of 93Zr

Abstract In order to confirm a prediction made by Talmi 5 ), the gamma rays following the beta decay of the 10.25 h fission product 93 Y were measured using a Ge(Li) spectrometer. In addition, the two-dimensional Ge-NaI coincidence spectrum was observed and the level scheme of 93 Zr was derived. The level scheme of 93 Zr presented here generally agrees with the level scheme derived by Knight et al. 8 ), and with the levels obtained by Cohen and Chubinsky 9 ) except for a few minor changes and a more exact energy determination. A level at 1167.7 keV was tentatively established and it was suggested that this is the 9 2 + level predicted by Talmi 5 ).

The determination of non-linear parameters and their standard deviations from least-squares residuals

Abstract The mathematical relationship existing between the sum of the squares of weighted residuals, χ 2 and the parameters determined by least-squares fitting procedures is investigated. This relationship is shown to contain explicity the variance of the calculated parameters. Examples are given in which this formulation is used in the least-squares estimation of non-linear parameters and their standard deviations.

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.

The decay of Br82

Abstract A re-examination of the decay of 36 h Br 82 has revealed the presence of two new transitions at 220±10 and 1648±10 keV. The intensity of these gamma rays is 0.8% and together with a 777 keV transition they form a triple cascade. This branch leads to a level at 2426±15 keV. Transitions at 250, 350, 1800 and 2000 keV previously reported have not been found and appear to be attributable to summing and scattering effects.

A two parameter centroid shift method for measuring nuclear lifetimes

Abstract A delayed coincidence technique for measuring nuclear lifetimes in the range of 100 ps is described. The start-stop time interval is recorded along with the stop energy in a two parameter array S ( E , t ) and the shape of the centroid-energy function 〈 S ( E , t )〉 in the prompt region of the spectrum is determined and extrapolated to the delayed region in order to obtain the centroid shift. The lifetime of the 31.2 keV level in 28 Al −T 1 2 = 2.15±0.06 ns and of the 279 keV level in 203 Tl − T 1 2 = 282±15 ps have been measured using this method. As a more direct verification of the technique, a source was displaced through measured distances relative to a second fixed source and the observed centroid shifts compared to the values predicted using the speed of light.