Nature of yrast excitations near N=40: Level structure of Ni-67

Excited states in Ni-67 were populated in deep-inelastic reactions of a Ni-64 beam at 430 MeV on a thick U-238 target. A level scheme built on the previously known 13 micro-s isomer has been delineated up to an excitation energy of ~5.3 MeV and a tentative spin and parity of (21/2-). Shell model calculations have been carried out using two effective interactions in the f5/2pg9/2 model space with a Ni-56 core. Satisfactory agreement between experiment and theory is achieved for the measured transition energies and branching ratios. The calculations indicate that the yrast states are associated with rather complex configurations, herewith demonstrating the relative weakness of the N=40 subshell gap and the importance of multi particle-hole excitations involving the g9/2 neutron orbital.Comment: Accepted by Physical Review

Variation with mass of \boldmath{B(E3; 0_1^+ \to 3_1^-)} transition rates in A=124−134A=124-134 even-mass xenon nuclei

$B(E3; 0_1^+ \to 3_1^-)$ transition matrix elements have been measured for even-mass $^{124-134}$Xe nuclei using sub-barrier Coulomb excitation in inverse kinematics. The trends in energy $E(3^-)$ and $B(E3; 0_1^+ \to 3_1^-)$ excitation strengths are well reproduced using phenomenological models based on a strong coupling picture with a soft quadrupole mode and an increasing occupation of the intruder $h_{11/2}$ orbital.Comment: 5 pages, 4 figures, PRC in pres

Investigating the role of Cu-oxo species in Cu-nitrate formation over Cu-CHA catalysts

The speciation of framework-interacting Cu(II) sites in Cu-chabazite zeolite catalysts active in the selective catalytic reduction of NO(x) with NH(3) is studied, to investigate the influence of the Al content on the copper structure and their reactivity towards a NO/O(2) mixture. To this aim, three samples with similar Cu densities and different Si/Al ratios (5, 15 and 29) were studied using in situ X-ray absorption spectroscopy (XAS), FTIR and diffuse reflectance UV-Vis during pretreatment in O(2) followed by the reaction. XAS and UV-Vis data clearly show the main presence of Z(2)Cu(II) sites (with Z representing a framework negative charge) at a low Si/Al ratio, as predicted. EXAFS wavelet transform analysis showed a non-negligible fraction of proximal Z(2)Cu(II) monomers, possibly stabilized into two 6-membered rings within the same cage. These sites are not able to form Cu-nitrates by interaction with NO/O(2). By contrast, framework-anchored Z[Cu(II)(NO(3))] complexes with a chelating bidentate structure are formed in samples with a higher Si/Al ratio, by reaction of NO/O(2) with Z[Cu(II)(OH)] sites or structurally similar mono- or multi-copper Z(x)[Cu(II)(x)O(y)] sites. Linear combination fit (LCF) analysis of the XAS data showed good agreement between the fraction of Z[Cu(II)(OH)]/Z(x)[Cu(II)(x)O(y)] sites formed during activation in O(2) and that of Z[Cu(II)(NO(3))] complexes formed by reaction with NO/O(2), further confirming the chemical inertia of Z(2)Cu(II) towards these reactants in the absence of solvating NH(3) molecules

In-beam spectroscopy of medium- and high-spin states in 133^{133}Ce

Medium and high-spin states in $^{133}$Ce were investigated using the $^{116}$Cd($^{22}$Ne, $5n$) reaction and the Gammasphere array. The level scheme was extended up to an excitation energy of $\sim22.8$ MeV and spin 93/2 . Eleven bands of quadrupole transitions and two new dipole bands are identified. The connections to low-lying states of the previously known, high-spin triaxial bands were firmly established, thus fixing the excitation energy and, in many cases, the spin parity of the levels. Based on comparisons with cranked Nilsson-Strutinsky calculations and tilted axis cranking covariant density functional theory, it is shown that all observed bands are characterized by pronounced triaxiality. Competing multiquasiparticle configurations are found to contribute to a rich variety of collective phenomena in this nucleus.Comment: 20 pages, 11 figure