Transient-field G-factor Measurement of the 1st 2+ States In the N = 82 Nuclei Ce-140, Nd-142 and Sm-144

The g-factor of the first 2+ states in three stable N = 82 nuclei, Ce-140, Nd-142 and 144Sm, have been measured using the transient magnetic field technique. The levels under study were Coulomb excited with 110-116 MeV S-32 beams and spin precession after passing a thin polarized iron foil was measured. The field strength has been checked using the first 2+ state in Sm-148 as internal calibration. The obtained values were 0.97 (9), 0.84 (7), 0.76 (11) for Ce-140, Nd-142 and 144Sm, respectively. These remarkably lower values with respect to shell-model predictions in a proton subspace are explained in terms of neutron core excitation by quasiparticle random-phase-approximation calculations

Bands and Coulomb effects in 50Cr

An extensive spectroscopic study of 48V has been performed using fusion-evaporation reactions to deduce the decay scheme and to measure transition probabilities through the Doppler shift attenuation method. Experimental levels were grouped into five bands, labeled with Nilsson configurations. Bands become nearly spherical approaching band termination. Large-scale shell model calculations were performed, producing results in very good agreement with the experimental data

Investigations of 159-163Dy using Incomplete Fusion Reactions

The isotopes Dy159-163 have been investigated using the incomplete fusion reactions Li-7 --> Gd-158,Gd-160 at beam energies of 8 MeV/u. The gamma-rays were detected in the GASP spectrometer in coincidence with the fast charged particles detected in the ISIS silicon ball. The level schemes of all five isotopes could be amply extended. The most important result was the observation of both the ground state and Stockholm bands in Dy-162 up to high spin covering the band crossing region. The crossing in this nucleus is shifted to a higher frequency in comparison to the lighter Dy isotopes. The interaction strength between the two bands could be determined with high precision and with this result, a full oscillation of the interaction strength from one node to the next within an isotopic chain could be observed for the first time

Backbending Region Study in 160, 162Dy using Incomplete Fusion Reactions

The incomplete fusion reactions 7Li\u20d7158,160Gd at beam energies of 8 MeV/nucleon have been used to study the first band crossing region in the heavy stable Dy isotopes 160,162Dy. The \u3b3 rays were detected in the GASP spectrometer in coincidence with fast charged particles detected in the ISIS silicon ball. We succeeded to observe the first backbending in 162Dy at a crossing frequency of \u127\u3c9 48350\u2002keV, a value much higher than expected from other nuclei in this mass region. Moreover, for the first time in a nucleus with a very large interaction strength, the yrare band in 160Dy could be established up to rather high spin (I=20\u127) allowing for a precise determination of the interaction strength between the ground state and the Stockholm band, |Vg-S|=219(2)\u2002keV. Together with |Vg-S|=14(2)\u2002keV determined for the corresponding interaction in 162Dy, a full oscillation of the strengths from one node to the next could be observed within an isotopic chain. In addition to the ground state and Stockholm bands, many other known bands in the two nuclei were considerably extended to higher spin and the experimental results are compared to calculations within the projected shell model

Coincidence Recoil-Distance Doppler-Shift Lifetime Measurements in 128Ba

Mean lifetimes of 24 excited states in Ba-128 populated via the Cd-116(O-16,4n) reaction at E = 76 MeV were measured by means of the recoil-distance Doppler-shift method in coincidence mode. A new version of the differential decay-curve method which takes into account the velocity distribution of the recoils and the effect of the Doppler-shift attenuation in the stopper was applied for the lifetime determination. The B(E2) values in the ground-state band indicate a reduction of the transition strengths which may be partly explained by the O(6) limiting case of the interacting boson model or alternatively, by rotationally induced changes in the single-particle level structure at spins higher than I-pi = 4(+). The general collective (or Frankfurt) model is found to describe well the intraband transition strengths in the quasi-gamma band which also exhibit the features characteristic for a K = 2 (h) over bar rotational band. However, none of the collective models applied can describe in a consistent way all observed properties of the low-lying collective states. The newly measured B(E2,I-->I-2) and B(M1,I-->I-1) transition strengths reconfirm the configuration pi h(11/2)d(5/2) of the negative-parity semide-coupled bands. The lowest levels of the higher-lying "dipole'' band in Ba-128, which is built on the high-K four-quasiparticle prolate configuration (pi h(11/2)d(5/2)) x (nu h(11/2)g(7/2)), are studied

Lifetimes in the Middle of 1f7/2 Shell: Cross-conjugated nuclei 47V and 49Cr

DSAM lifetimes have been determined in the middle of View the MathML source shell for the cross-conjugated nuclei 47V and 49Cr, populated with the reaction 28Si on 28Si at 115 MeV using a Au backed target. B(E2) and B(M1) reduced rates agree very well with large scale shell model predictions. The interplay between spherical and collective structures is discussed

High-K Band of Unnatural Parity in 49Cr

The nucleus 49Cr has been studied using the reactions 28Si(28Si,\u3b12pn) at 115 MeV and 46Ti(\u3b1,n) at 12 MeV, respectively. A high-K band with K\u3c0=13/2+ has been identified, whose bandhead acts as an yrast trap for the low-lying levels with positive parity. This peculiar phenomenon is well reproduced by large-scale shell model calculations in the pf configuration space plus a proton hole in the 1d3/2 orbital. As an essential part of the work, lifetimes of some nonyrast states, as well as of a state in the K\u3c0=5+ band in 50Mn, have been determined using the Doppler shift attenuation method

Low-Lying Bands with Different Quadrupole Deformation in 133Nd

The mean lifetimes of ten states in 133Nd excited via the reaction 104Pd(32S,2pn) at E32S=135 MeV were measured by means of the recoil-distance Doppler-shift method. The spectra obtained by setting a gate on the shifted component of a transition directly feeding the level of interest were analyzed within the framework of the differential decay-curve method. The intraband transition strengths are compared to calculations within the particle plus rotor model which reveal differences in the quadrupole deformations \u3b5 and \u3b3 of the bands studied

48V: An experimental and theoretical paradigm in the middle of the 1f7/2 shell

An extensive spectroscopic study of 48V has been performed using fusion-evaporation reactions to deduce the decay scheme and to measure transition probabilities through the Doppler shift attenuation method. Experimental levels were grouped into five bands, labeled with Nilsson configurations. Bands become nearly spherical approaching band termination. Large-scale shell model calculations were performed, producing results in very good agreement with the experimental data