Levels in154Eu populated by thermal neutron capture

Abstract

The level scheme of 1S~Eu has been investigated by means of thermal neutron capture yrays and conversion electrons. The high energy y-ray spectrum from thermal neutron capture in enriched 153Eu has been studied in the energy range of 5700 to 6500 keV. Low energy y radiation has been observed with Ge(Li) and Si(Li) detectors from 5 to 300 keV and conversion electrons have been measured from 15 to 300keV. Low energy (n, yy) coincidences and half lives of transitions have been measured. The data, combined with three very recent studies of the 8-isomer decay in iS~Eu has led to the construction of a level scheme with 12 excited levels.Nuclear Reaction 153Eu(n ' 7), E, = thermal, measured E.;, I~, Ece, Ice , yy-coincidence, halflives, 154Eu deduced levels.

Low-lying excitations in the odd-odd nucleus154Eu

“…Almost all low-energy gamma rays connected with those isomers in previous papers [3,4] have been identified in the present study. Thus the results of these experiments largely confirm the earlier data, but many other, new gamma rays were also included in our level schemes as well.…”

“…St6ffl et al [3] have reported 7-rays at energies of 80.8 and 100.1 keV with the multipolarity assignments of E 1. If the latter is the same transition we have detected, then there is disagreement both in its multipolarity and its position in the level scheme.…”

“…3 also include numerous peaks with energies underlined. They are all new in respect to [3][4][5], but we will' give a reliable location for most of them based on their energies, observed intensities and mutual prompt coincidence relationships. A spectrum gated with the 75 keV transition provides tentative information on which of them might belong together and fortunately the prompt 101 keV gate itself yielded more insight to the classification, as the added spectrum in Fig.…”

“…In the neighbouring nucleus 154Eu ' the decay of the 47 min long-lived, 8-isomer at 145 keV has been investigated in [2]. This together with the results of a previous 77-coincidence measurement in an (n, 7) study [3] has provided a firm basis for later investigations. A more recent series of measurements with the (n, 7)-and (d, p)-reactions summarized in [4,5] yielded a lot of additional information on individual lowenergy excitations in l S4Eu.…”

“…For example, the prompt coincidence data undoubtedly indicate the existence of a very regular ground band populated up to the spin value of (10-). Placings of the first-time observed transitions as well as the spin assignments tentatively suggested are entirely based on the established levels [3][4][5]. …”