M. Ionescu-Bujor

Lifetimes of a shears band in 139Sm

Abstract Lifetimes have been measured in 139Sm with the DSAM method, using the reaction 62Ni(81Br,p3n)139Sm at 350 MeV. In the negative-parity regular dipole band based on the 25 2 − state at 3325 keV values of 0.60(21), 0.40(14) and 0.25(8) ps were found for the 337, 409 and 473 keV transitions, respectively. The deduced B(M1) and B(E2) are in agreement with the predictions of the tilted axis cranking model, allowing a triaxial equilibrium shape for the assumed νh 11 2 ⊗ πh 11 2 2 configuration.

STRUCTURE OF NEUTRON–RICH NUCLEI FROM DEEP–INELASTIC REACTIONS

Neutron rich nuclei have been populated using the 82Se+192Os deep-inelastic reaction. New experimental results on 188W, 188,190Os target-like nuclei, as well as 74,76,78Ge beam-like nuclei are presented.

Evolution from spherical to various deformed shapes in the odd-odd 59136Pr77 nucleus

Abstract The level scheme of the doubly odd 136Pr nucleus has been investigated via the 136Ce(p,n), 122Sn(19F,5n) and 110Pd(30Si,p3n) reactions at beam energies of 14, 84 and 125 MeV, respectively. A complex decay scheme has been established for the 90 ns isomeric level with Ex = 594.7 keV and Jπ = 6+. The two previously reported bands, one based on the πh 11 2 ⊗ νh 11 2 configuration and one with suggested negative parity consisting of only dipole transitions, have been extended at higher spins and connected firmly to the 6+ isomer. Six new bands have been also identified: two consist of strong dipole and crossover quadrupole transitions, whereas the other four, very weakly populated, consist of only quadrupole transitions. The observed level structures are compared to theoretical calculations performed within the interacting boson model for odd-odd nuclei (IBFFM) and the cranked shell model. The experimental B (M1) B (E2) ratios of the yrast band are well reproduced by the IBFFM calculations, while those of the other semi-decoupled structures are in good agreement with the values obtained from the semiclassical model of Donau.

g-factors in the ground state and γ-bands in 164,166,168Er

Abstract The g -factors of the ground state band members up to the 10 + level and of the 2 + state in the γ-vibrational band have been measured in 164,166,168 Er using the Coulomb excitation transient field technique. In the g-band the g -factor values were found to be nearly constant as a function of spin. For the 2 + states of the γ-band, values about 20% larger than those in the g-band have been determined. This latter fact is consistent with the known decay properties of the γ-band.

Superdeformed band g-factor in 133Nd

Abstract A g-factor measurement in the superdeformed band of 133Nd has been performed by applying the transient field method in coincidence mode with the multidetector array GASP. The 133Nd nuclei were populated by the 104Pd(32S,2pn) reaction at a bombarding energy of 135 MeV. Polarized Gd has been used as ferromagnetic host. A mean g-factor of g = 0.31(8) has been determined at the I π = 41 2 + superdeformed state. The experimental value is compared with theoretical predictions and supports the assignment of the superdeformed band to the ν[660] 1 2 + Nilsson intruder orbital.

g-factors of the lowest 2+ and 4+ states in198, 200, 202Hg

Theg-factors of the 21+ and 41+ states in198,200,202Hg were simultaneously measured by means of the transient-field perturbed angular correlation method in Coulomb excitation using multi-isotopic targets and thin polarized Gd foils as ferromagnetic host. Theg(21+) andg(41+) were found identical within errors in198, 200Hg, while in200Hg lowerg-factor values have been determined. The experimentalg-factors were compared with the predictions of the pairing-plus-quadrupole, dynamical deformation and interacting boson models.

Decay properties and magnetic moment of the 548 keV level in 136Pr

The decay properties and the magnetic moment of the 548 keV isomeric state in 136Pr populated in the 122Sn (19F, 5n) reaction were investigated by pulsed beam γ-ray spectroscopy and TDPAD measurements using as host metallic Pt at room temperature. The determined characteristics of the isomeric state, T12 = 90(2) ns, Jπ = 4+ and g = + 0.570(19), are explained by assigning to it a dominant configuration π(1h112)⊗ν(1h112) and an extremely small contribution of configurations involving proton and neutron positive-parity orbits. Firm spin assignment for the upper energy collective structures can be deduced.

Gryomagnetic ratios of low-lying states in 192,194,196Pt

Abstract Gyromagnetic ratios of the 2 1 + and 4 1 + states in 192,194,196 Pt and of the 2 2 + states in 192,194 Pt were simultaneously measured by the transient-field perturbed angular correlation method in Coulomb excitation using a multi-isotopic Pt target and thin polarized Fe and Gd foils as ferromagnetic hosts. The experimental g -factors were found identical within errors. These and previous existing data indicate the independence of the low-lying state g -factors in even stable Pt nuclei with respect to the spin and neutron number.

Yrast states in 188, 190Os nuclei

Yrast states in neutron rich nuclei 188Os and 190Os have been populated using the deep-inelastic reaction 82Se + 192Os at 460 MeV beam bombarding energy. A thick 192Os target (>50 mg/cm2) with 0.2 mm Ta backing was used to stop all of the recoils in the target, minimising the broadening of the lines due to Doppler shift. High fold γ-γ coincidences were aquired with the 4π spectrometer GASP detector array. Three and two dimensional gamma-ray matrices were used to construct level schemes of the nuclei of interest up to an yrast state of 22.

Quadrupole moment of the Kπ=14+ isomer in 176W

The spectroscopic quadrupole moment of the I π = K π = 14 + , T1/2 = 41 ns isomer in 176 W has been measured by observing the time-dependent quadrupole interaction pattern of the decay radiation from the isomer implanted in the polycrystalline metallic Tl host. The result |Qs |= 5.99( +0.66 −0.82 )e b corresponds to an intrinsic quadrupole moment Q0 = 7.37( +0.81 −1.01 )e b, similar to the ground-state band quadrupole moment. The value gR = 0.269(34) has been deduced for the rotational g factor of the 14 + isomer on the basis of the measured static moments and branching ratios in the associated band.  2002 Elsevier Science