Search

High spin states in ${}^{104}\mathrm{Sn}$ were identified in the reaction ${}^{58}\mathrm{Ni}{(}^{50}\mathrm{Cr}$, $2p2n)$ at 200 and 205 MeV beam energies. The $\ensuremath{\gamma}$-ray energies, intensities, multipolarities, and lifetimes of high spin states were measured with the GASP spectrometer array in combination with a plunger apparatus by means of the recoil distance Doppler shift method. The deduced level scheme and transition probabilities are compared to the results of large-scale shell model calculations using three independent two-body interactions. The agreement of the level energies is satisfactory, except for a cascade of dipole transitions at high spins. The general good agreement found for $E2$ transition strengths implies a large effective neutron polarization charge. The shell-model calculations do not account for the measured enhanced $E3$ transitions for which a core excited octupole phonon admixture is indicated.

The lifetimes of three low-lying states in the superdeformed (SD) yrast band of {sup 194}Hg were measured applying the recoil-distance Doppler-shift method. As the deduced transition quadrupole moments Q{sub t} are equal within the experimental uncertainties to those extracted from a Doppler-shift attenuation method (DSAM) measurement for the high-lying states of the band, the assumption that the decay out of SD bands does not strongly affect the structure of the corresponding states is corroborated. By a simple mixing model, the decay can be described assuming a very small admixture of normal-deformed (ND) states to the decaying SD states. The deduced ND mixing amplitudes for the yrast SD bands in {sup 192,194}Hg and {sup 194}Pb are presented along with average transition quadrupole moments for the lower parts of the excited SD bands in {sup 194}Hg. {copyright} {ital 1997} {ital The American Physical Society}

Neutron particle-hole states in the doubly magic nucleus 208 Pb were investigated using a Euroball Cluster detector and five usual HPGe detectors at the Osiris cube spectrometer in Cologne. 126 γ-ray transitions with energies up to 7.2 MeV could be detected 14 for those for the first time. The states were excited with the 208 Pb( p , p ' γ ) 208 Pb reaction via isobaric analogue resonances in 209 Bi at E p = 16.5, 17, 17.45, 17.5 and 18.5 MeV and though the subcoulomb 207 Pb( d , pγ ) 208 Pb reaction at E d = 10 MeV. For most of the excited states assignments for the particle and/or the hole component of the configuration could be made, 22 of these are new.

An in-beam experiment with the subcoulomb reaction 209Bi(3He, d*γγ)210Po at 20.5 MeV was performed with two Euroball Cluster detectors in Cologne. It closed the gap between the low energy levels of the level-scheme and the high energy levels found in 209Bi(3He, d)210Po and 208Pb(4He, t)210Po particle experiments. New branchings have been found and the (3He, d*γγ) reaction below the coulomb-barrier has been used successfully.

The mean lifetimes of the ${25/2}^{+}$, ${21/2}^{+}$, and ${17/2}^{+}$ states in the highly deformed (HD) band of $^{133}\mathrm{Nd}$, excited via the reaction $^{104}\mathrm{Pd}$($^{32}\mathrm{S}$,2$\mathit{pn}$)$^{133}\mathrm{Nd}$, have been measured using a recoil distance Doppler-shift method. The decay out of the HD band occurs as a result of an admixture of normally deformed (ND) components into the HD states' wave function. The consistency in the mixing amplitude was assessed from the measured lifetimes, branching ratios, and quadrupole moments of the HD and the ND bands. This analysis unequivocally confirms the earlier approach to explain the decay-out mechanism.

For the investigation of the collectivity and the structure of the intruder bands with positive and negative parity in 114 Sn, coincidence lifetime measurements using the recoil distance Doppler shift (RDDS) and the Doppler-shift attenuation (DSA) methods were performed at the GASP spectrometer at the INFN-Laboratori in Legnaro. Excited nuclear states were populated with the reaction 100 Mo( 18 O,4n) 114 Sn. For analysis the differential decay curve method was used in the γγ -coincidence mode. In total 31 lifetimes could be obtained, belonging to 11 and 13 states in the positive- and negative-parity intruder bands, respectively, and to 7 spherical states. This work enhances our knowledge of low-lying collectivity among the Sn isotopes near the mid-shell region.