A partial level scheme of Gd, established in this work, is displayed in
Fig. 1. For the odd-spin negative-parity band we confirm that
the E2 transitions vanish below the state. The intensity
transition is very weak and could not be
firmly established. In fact, this transition is part of a doublet (400-402 keV) in coincidences
with another doublet at 470 keV both present in the odd-spin band and the even spin band.
Therefore gating on the 470 keV line to extract the 402 keV intensity would bring
in any case residuel contamination from the 400 keV line.
Partial decay scheme of Gd showing the ground-state band,
odd- and and even-spin negative parity bands and the newly
established interconnecting transitions are shown.
The E1 transitions de-exciting the state and the E2 transition connecting the
(reported in previous experiments) from the even-spin band cannot be confirmed
by our results. However,
coincidences allowed us to clarify
a number of uncertainties caused by the presence of doublet- and even
triplet-lines in the spectrum of this nucleus. Moreover, we were able to examine
the transitions in the medium spin range and firmly establish new inter-band
transitions with of 538, 469 and 390 keV. Angular distributions will
be analysed in the near future to determine the character (stretched M1 or
non-stretched E2) of these transitions. Table 1 shows some
preliminary (E2)/(E1) ratios that we have found, compared to the results
of the previous studies of Refs. [4,5]. For the and
states of the odd-spin negative-parity band, the transition strength
ratios are of the same order of magnitude as previously reported, while for
higher spin states they could not be determined because of the cut-off in
angular momentum due to the use of the -beam.
Branching ratios (E2)/(E1) in units fm. (a) Established in the present work
- in comparison with: (b) Previous results from Refs. [4,5].
Only upper limits are
established for the lowest spins, however this information represents already
a progress since no earlier
publication quotes any estimates for the and transitions. For the even-spin negative-parity band the
B(E2)/B(E1) ratios decrease with decreasing spin and are up to two orders of
magnitude higher than those of the odd-spin negative-parity band.
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