High-spin states of the ital N=49,50 nuclei sup 85,86Kr have been investigated via the reactions sup 82Se(sup 7Li,ital p3ital n) or sup 82Se(sup 7Li,ital p2ital n), respectively, using 32 MeV sup 7Li ...ions. In order to suppress gamma rays arising from pure neutron evaporation the measurements of angular distributions and relative excitation functions of the gamma rays as well as gammagamma coincidences have been performed in particle-gamma coincidence modes. Additional information on excited states in sup 85Kr has been obtained in connection with the sup 82Se(alpha,ital n) reaction at beam energies between 13 and 21 MeV. The level scheme of sup 85Kr has been extended by a new sequence of high-spin states with excitation energies up to 4.8 MeV and tentative spins up to (23/2) that is built on top of the 17/2sup + mus isomer at 1991.8 keV. For sup 86Kr a new level scheme of high-spin states with excitation energies up to 7.9 MeV and tentative spins up to (12) has been observed for the first time. The level sequences observed in sup 85,86Kr are interpreted on the basis of shell-model calculations in the configuration space 1ital psub 3/2, 0ital fsub 5/2, 1ital psub 1/2, and 0ital gsub 9/2 for the protons and 0ital gsub 9/2 or 0ital gsub 9/2, 1ital dsub 5/2 for the neutrons in sup 85Kr or sup 86Kr, respectively. The inclusion of neutron-core excitations in the calculations for sup 86Kr results in a remarkably improved agreement between experimental and calculated level energies. In this way considerable contributions of neutron-core excitations are strongly suggested for the positive-parity yrast states with spins 7h bar, 9h bar, and 10h bar.
Phys.Rev.Lett. 83 (1999) 1303-1306 The nucleus 94Mo was investigated using a powerful combination of
gamma-singles photon scattering experiments and gamma-gamma-coincidence studies
following the ...beta-decay of 94mTc. The data survey short-lived J^pi=1+,2+
states and include branching ratios, E2/M1 mixing ratios, lifetimes, and
transition strengths. The mixed-symmetry (MS) 1+ scissors mode and the 2+ MS
state are identified from M1 strengths. A gamma transition between MS states
was observed and its rate was measured. Nine M1 and E2 strengths involving MS
states agree with the O(6) limit of the interacting boson model-2 using the
proton boson E2 charge as the only free parameter.
Measurements of the linear polarization of resonantly scattered photons have been used for model independent parity assignments in nuclear resonance fluorescence experiments (NRF). Previous NRF ...investigations of the even-even Nd isotopes were completed by polarization measurements on the transitional nucleus sup 146Nd. With these new parity assignments the systematics of low lying ital M1 strengths can be studied along the transition from spherical to deformed nuclear shapes. The total ital M1 strength in the excitation energy range of 2--4 MeV in the investigated even-even Nd isotopes increases proportionally to the square of the deformation parameter. These findings represent a reliable confirmation of the results recently reported for the Sm isotopes by the Darmstadt group. This deformation dependence can be explained by various recent theoretical approaches.
Phys.Rev. C62 (2000) 014309 The odd-mass $^{117}$Sn nucleus was investigated in nuclear resonance
fluorescence experiments up to an endpoint energy of the incident photon
spectrum of 4.1 MeV at the ...bremsstrahlung facility of the Stuttgart University.
More than 50 mainly hitherto unknown levels were found. From the measurement of
the scattering cross sections model independent absolute electric dipole
excitation strengths were extracted. The measured angular distributions
suggested the spins of 11 excited levels. Quasi-particle phonon model
calculations including a complete configuration space were performed for the
first time for a heavy odd-mass spherical nucleus. These calculations give a
clear insight in the fragmentation and distribution of the $E1$, $M1$, and $E2$
excitation strength in the low energy region. It is proven that the $1^{-}$
component of the two-phonon $2^{+}_{1} \otimes 3^{-}_{1}$ quintuplet built on
top of the $1/2^{+}$ ground state is strongly fragmented. The theoretical
calculations are consistent with the experimental data.
An angular momentum dependence of the parity splitting in the alternating parity bands of nuclei with strong octupole correlations is considered basing on the model of the octupole motion in a ...one-dimensional potential well conserving axial symmetry. A sign reversal of the parity splitting at higher values of the angular momentum is interpreted as a result of the Coriolis coupling to K=1 octupole mode. New experimental data on the spectra of the alternating parity octupole bands are used.
