0000000000002598
AUTHOR
D. Curien
Identification of new transitions feeding the high-spin isomers in $^{139}$Nd and $^{140}$Nd nuclei
The population of the high-spin isomers in 139Nd and 140Nd was investigated using the 96Zr(48Ca,xn) reaction and the JUROGAM + RITU + GREAT setup employing the recoil decay tagging technique. Three transitions feeding the 23/2+ isomer in 139Nd and two transitions feeding the 20+ isomer in 140Nd were identified. The newly observed transitions allowed the excitation energy of the isomer to be established in 139Nd and to assign configurations to the states and bands deexcited by the observed transitions in both nuclei. peerReviewed
Structure of the As, Ge, Ga nuclei
Abstract The level structures of the N = 50 83As, 82Ge, and 81Ga isotones have been investigated by means of multi-nucleon transfer reactions. A first experiment was performed with the CLARA–PRISMA setup to identify these nuclei. A second experiment was carried out with the GASP array in order to deduce the γ-ray coincidence information. The results obtained on the high-spin states of such nuclei are used to test the stability of the N = 50 shell closure in the region of 78Ni ( Z = 28 ). The comparison of the experimental level schemes with the shell-model calculations yields an N = 50 energy gap value of 4.7(3) MeV at Z = 28 . This value, in a good agreement with the prediction of the fini…
High-spin spectroscopy of 140Nd
The population of the high-spin states in 140Nd was investigated using the reaction 96Zr(48Ca,4n). The results from two experiments, one with the EUROBALL array and one with the JUROGAM II + RITU + GREAT setup employing the recoil decay tagging technique, have been combined to develop a very detailed level scheme for 140Nd. Twelve bands of quadrupole transitions and eleven bands of dipole transitions were identified and their connections to low-lying states were established. Calculations using the cranked Nilsson-Strutinsky and the tilted axis cranking models were used to interpret the observed structures. The overall good agreement between the experimental results and the calculations assu…
Backbending in the pear-shaped 223(90)Th nucleus: Evidence of a high-spin octupole to quadrupole shape transition in the actinides
International audience; Relatively neutron-rich thorium isotopes lie at the heart of a nuclear region of nuclei exhibiting octupole correlation effects. The detailed level structure of Th223 has been investigated in measurements of γ radiation following the fusion-evaporation channel of the Pb208(O18,3n)Th223 reaction at 85 MeV beam energy. The level structure has been extended up to spin 49/2, and 33 new γ rays have been added using triple-γ coincidence data. The spins and parities of the newly observed states have been confirmed by angular distribution ratios. In addition to the two known yrast bands based on a K=5/2 configuration, a non-yrast band has been established up to spin 35/2. We…
First candidates for γ vibrational bands built on the [505]11/2⁻ neutron orbital in odd-A Dy isotopes
Rotational structures have been measured using the Jurogam II and GAMMASPHERE arrays at low spin following the 155Gd(α,2n)157Dy and 148Nd(12C,5n)155Dy reactions at 25 and 65 MeV, respectively. We report high-K bands, which are conjectured to be the first candidates of a Kπ=2+γ vibrational band, built on the [505]11/2− neutron orbital, in both odd-A155,157Dy isotopes. The coupling of the first excited K=0+ states or the so-called β vibrational bands at 661 and 676 keV in 154Dy and 156Dy to the [505]11/2− orbital, to produce a Kπ=11/2− band, was not observed in both 155Dy and 157Dy, respectively. The implication of these findings on the interpretation of the first excited 0+ states in the cor…
Octupole correlations in the structure of 0$_2^+$ bands in the N=88 nuclei 150Sm and 152Gd
Knowledge of the exact microscopic structure of the 01 + ground state and first excited 02 + state in 150Sm is required to understand the branching of double β decay to these states from 150Nd. The detailed spectroscopy of 150Sm and 152Gd has been studied using (α,xn) reactions and the γ -ray arrays AFRODITE and JUROGAM II. Consistently strong E1 transitions are observed between the excited Kπ = 02 + bands and the lowest negative parity bands in both nuclei. These results are discussed in terms of the possible permanent octupole deformation in the first excited Kπ = 02 + band and also in terms of the “tidal wave” model of Frauendorf. peerReviewed
Octupole correlations in the structure of02+bands in theN=88nuclei150Sm and152Gd
Knowledge of the exact microscopic structure of the 0${}_{1}$${}^{+}$ ground state and first excited 0${}_{2}$${}^{+}$ state in ${}^{150}$Sm is required to understand the branching of double \ensuremath{\beta} decay to these states from ${}^{150}$Nd. The detailed spectroscopy of ${}^{150}$Sm and ${}^{152}$Gd has been studied using (\ensuremath{\alpha},xn) reactions and the \ensuremath{\gamma}-ray arrays AFRODITE and JUROGAM II. Consistently strong $E$1 transitions are observed between the excited ${K}^{\ensuremath{\pi}}$ $=$ 0${}_{2}$${}^{+}$ bands and the lowest negative parity bands in both nuclei. These results are discussed in terms of the possible permanent octupole deformation in the …
First candidates for $\gamma$ vibrational bands built on the $[505]11/{2}^{-}$ neutron orbital in odd-$A$ Dy isotopes
Rotational structures have been measured using the Jurogam II and GAMMASPHERE arrays at low spin following the 155Gd({\alpha},2n)157Dy and 148Nd(12C, 5n)155Dy reactions at 25 and 65 MeV, respectively. We report high-K bands, which are conjectured to be the first candidates of a K{\pi}= 2+ {\gamma} vibrational band, built on the [505]11/2- neutron orbital, in both odd-A 155, 157Dy isotopes. The coupling of the first excited K=0+ states or the so-called \b{eta} vibrational bands at 661 and 676 keV in 154Dy and 156Dy to the [505]11/2- orbital, to produce a K{\pi}=11/2- band, was not observed in both 155Dy and 157Dy, respectively. The implication of these findings on the interpretation of the f…
Lifetime measurement of neutron-rich even-even molybdenum isotopes
D. Ralet et al. -- 11 pags., 10 figs., 3 tabs.
Spectroscopy of 253No and its daughters
Abstract New high-statistics data have been obtained on the decay properties of 253 No and its daughters using the reaction 207 Pb( 48 Ca, 2n) 253 No. This was made possible thanks to an improved transmission of fusion–evaporation residues through the VASSILISSA recoil separator and an increased efficiency of the GABRIELA detector setup. The decay schemes of 253 No and 249 Fm have been revisited. The known level scheme of 249 Fm has been confirmed, including a new level at 669 keV excitation energy. The observation of L X-rays in coincidence with the α decay of 249 Fm gives additional support to the ground-state configuration of 1 / 2 + [ 631 ] instead of 5 / 2 + [ 622 ] for 245 Cf. In both…
Stability of chiral geometry in the odd–odd Rh isotopes: spectroscopy of 106Rh
International audience; 136 P. Joshi et al. / Physics Letters B 595 (2004) 135–142AbstractThe nucleus 106Rh was populated using the reaction 96Zr(13C, p2n) at a beam energy of 51 MeV. γ -ray transitions wereidentified using the EUROBALL-IV γ -ray spectrometer and the DIAMANT charged particle array. The yrast band, which isbased upon a πg−19/2 ⊗ νh11/2 configuration, has been extended to I π = (22−). A new I = 1 band has been identified whichresides ∼ 300 keV above the yrast band. Core–quasiparticle coupling model calculations show reasonably good agreement withthe data. The properties of the two pairs of strongly coupled bands are consistent with a chiral interpretation for these states. 2…
Search for fingerprints of tetrahedral symmetry in 156gd
Theoretical predictions suggest the presence of tetrahedral symmetry as an explanation for the vanishing intra-band E2 transitions at the bottom of the odd-spin negative-parity band in 156Gd. The present study reports on experiment performed to address this phenomenon. It allowed to remove certain ambiguouities related to the intra-band E2 transitions in the negative-parity bands, to determine the new inter-band transitions and reduced probability ratios B(E2)/B(E1) and, for the first time, to determine the experimental uncertainties related to the latter observable. peerReviewed
Experimental evidence for chirality in the odd-A 105Rh
Abstract High-spin states in 105 Rh were populated by the 96 Zr( 13 C, p3n) reaction at beam energies of 51 and 58 MeV, and studied using the EUROBALL IV γ -ray spectrometer and the DIAMANT charged particle array. A pair of nearly degenerate Δ I = 1 three-quasiparticle bands with the same spins and parity have been observed. Comparison of the experimental results with tilted axis cranking calculations confirms the chiral character of the two bands, while arguments based on the excitation of particles within the π g 9 / 2 ν ( h 11 / 2 ) 2 configuration of the yrast band and comparison with the previously observed γ band exclude the other possible interpretations. This is the first experiment…
Low-lying electric dipole gamma-continuum for the unstable Fe-62,64 nuclei : Strength evolution with neutron number
6 pags., 4 figs.
AGATA-Advanced GAmma Tracking Array
WOS: 000300864200005