M. Aïche

M1 transitions between superdeformed states in 195Tl: the fingerprint of the i132 proton intruder orbital

Abstract Dipole transitions linking the superdeformed Yrast signature-partner bands in 195Tl have been observed using the EUROGAM 1 spectrometer. From the measurements of the photon decay branching ratios, taken together with the average quadrupole moment measured in neighbouring superdeformed nuclei, we find that the two signature partner superdeformed bands involve the excitation of the 81 st proton into the i 13 2 Ω= 5 2 intruder orbital

The yrast superdeformed band in 194Pb. Differences with 192Hg

The yrast superdeformed (SD) structure of 194Pb has been studied using the EUROGAM γ-ray spectrometer. New results have been obtained at low as well as at high spin values. At low frequency, the SD band has been extended to the lowest-spin SD state ever observed in the A ∼ 190 region. The energies of 194Pb and 192Hg SD bands are identical for ω < 0.25 MeV. However, they diverge for higher frequency, which rules out the idea that these two SD bands are identical. Moreover, the SD band of 194Pb is populated at lower spin values than that of 192Hg and de-excites towards normally-deformed (ND) states at a spin value lower than that of 192Hg. This suggests that the barrier separating the SD and ND minima in the potential energy surface is higher in 194Pb than in 192Hg.

High-spin spectroscopy of the reflection-asymmetric nucleus 221Ac

Abstract The high-spin state structure of the nucleus 221 Ac was investigated by means of the 209 Bi( 14 C, 2n) reaction at 63 and 65 MeV. Measurements consisted of in-beam γγ coincidences using the Château de Cristal multidetector array and of e − γ coincidences. Two alternating parity bands could be established in 221 Ac up to spin 35 2 h . Almost all of the states may be regrouped into parity doublets and the origin of these doublets is discussed.

New results on the superdeformed band in192Hg

AbstractNew results on the192Hg superdeformed band have been obtained with EUROGAM. The experiment has been performed with the160Gd(36S,4n) reaction at 159 MeV. Above 800 keV the γ-ray energies differ from the previously published ones. Thus the rise of the dynamical moment of inertia

Alternating parity bands in doubly odd 218Ac129 and octupole instability in the light actinide region

\mathfrak{F}^{(2)}

Fission Cross Sections and Fission‐Fragment Mass Yields via the Surrogate Reaction Method

above ħω=0.4 MeV is no longer observed. This is in better agreement with recent cranked Hartree-Fock-Bogoliubov calculations.

1ST OBSERVATION OF A SUPERDEFORMED NUCLEUS PRODUCED IN AN ALPHA-XN REACTION CHANNEL

Recent data from the EUROGAM array have revealed dipole transitions linking signature partner superdeformed bands in 194Tl and 195Tl nuclei. Measurements of the decay branching ratios, taken together with the average quadrupole moment of the neighboring superdeformed nuclei, enable the absolute M1 strengths to be determined. From these data and using the strong coupling model, we find that two SD bands in 195Tl are due to the 81st proton being in the [642]5/2+ orbital and four from the six SD bands in 194Tl correspond to a configuration where the intrinsic spins of the single proton and single neutron are aligned.

Hybridized bands and parity splitting in the odd-odd nucleus220Ac

Abstract High-spin states of doubly odd 218 Ac1 129 have been investigated using in-beam α, γ and conversion electron spectroscopy techniques through the 209 Bi( 12(13) C,3(4)n) fusion-evaporation reactions. The level scheme of 218 Ac shows three interconnected, alternating parity structures, each one linked by strong El transitions. Two of these bands are strikingly similar to the known scheme of the isotone 217 Ra and this analogy is shown to persist for the pair 220 Ac, 219 Ra. The relation between the structure of 218 Ac and its neighbors is thoroughly discussed showing that the first signals of octupole collectivity appear for N = 129.