Application of the Broad Energy Germanium detector: A technique for elucidating β -decay schemes which involve daughter nuclei with very low energy excited states

Abstract

A new technique of elucidating β-decay schemes of isotopes with large density of states at low excitation energies has been developed, in which a Broad Energy Germanium (BEGe) detector is used in conjunction with coaxial hyperpure germanium detectors. The power of this technique has been demonstrated on the example of 183 Hg decay. Mass-separated samples of 183 Hg were produced by a deposition of the low-energy radioactive-ion beam delivered by the ISOLDE facility at CERN. The excellent energy resolution of the BEGe detector allowed γ rays energies to be determined with a precision of a few tens of electronvolts, which was sufficient for the analysis of the Rydberg-Ritz combinations in the level scheme. The timestamped structure of the data was used for unambiguous separation of γ rays arising from the decay of 183 Hg from those due to the daughter decays.

New systematic features in the neutron-deficient Au isotopes

“…This has been handled variously with ultra-low energy singles conversion-electron spectroscopy [42,43] and with low-energy conversion-electron-γ-ray coincidence spectroscopy [8,13,14,44]. We attacked this problem in 183 Au [32] using the large number of deexcitation paths of the 1682.30 keV state, strongly populated in β decay (see above), combined with γ-ray spectroscopy employing, in part, the high-energy precision available using a BEGe detector operated at high gain (27 eV/ch). Such data, in combination with γ-γ coincidence spectroscopy, provide a 'map' of low-lying excited states with some use of the Rydberg-Ritz combination principle.…”

“…Such data, in combination with γ-γ coincidence spectroscopy, provide a 'map' of low-lying excited states with some use of the Rydberg-Ritz combination principle. This approach to elucidating complex decay schemes, with a high density of states at low energy is described in greater detail in [32].…”

“…Spectra corresponding to the early and late parts of the decay curves were produced, normalised and subtracted in such a way that events due to mother and daughter activity were separated. This technique is described in more detail in [32]. An example of such a deconvoluted conversion-electrum spectrum is shown in figure 2(b), where the peaks of daughter activities are subtracted.…”

“…Missing them usually leads to misinterpretation of the data. In this work we use a technique which we have developed in [32] in conjunction with the presently reported study to make an advance in addressing this issue by the use (to our knowledge the first-ever in decay spectroscopy) of a modern BEGe [29] detector with high energy resolution over a broad energy range, operated at high gain and in coincidence mode.…”

“…The time-gated and prompt coincidence spectra were reconstructed offline. Further details are given in [32].…”