M. Eschenauer

Multiple quadrupole “phonon” excitations in 130Ba

Abstract The low spin structure of 130Ba was investigated via the emitted γ-radiation following the β-decay of 130La. New “K = 0”- and “K = 4”- bands were identified. A comparison with the O(6) symmetry of the IBM is shown. A discussion of the low lying levels of the O(6) symmetry in terms of multiple quadrupole “phonon” excitations built on the ground state is given.

Low spin states in 130Ba

Abstract The low spin structure of 130 Ba has been investigated following the β + -decay of ground and medium spin isomeric states of 130 La. The lanthanum nuclei were produced at the Cologne FN-tandem accelerator using the reaction 120 Sn( 14 N,4n) 130 La. γγ-coincidence data was taken by means of the OSIRIS 6-cube spectrometer. Many new low lying levels were established. Of special interest are new “ K = 0”- and “K = 4”- bands . We give the level and transition energies, spins and parities, multipole mixing ratios and B (E2)-ratios obtained from this measurement. The low lying states of positive parity are discussed in the framework of the IBA-1 model and compared with results for the F-spin partner 126 Xe. The description is given in terms of a consistent-Q formalism near the dynamical O(6)-symmetry. A new scheme which gives analytical expressions for the O(6)-wave functions is presented. The scheme is still valid approximately in vicinity of O(6).

Resolution enhancement of gamma-spectroscopy data from neutron-damaged coaxial n-type HPGe-detectors

Abstract A new method has been developed to correct gamma-spectroscopy data for effects of charge carrier trapping in neutron-damaged coaxial n-type HPGe-detectors. In addition to the pulse height, the risetime of each signal is measured with standard nuclear spectroscopy electronics and both data are recorded on tape. From this data the amount of the pulse height deficit, which is due to the neutron damage, can be calculated for each event. The correction of the pulse height is done by software during the normal analysis of the listmode data. For the determination of the correction coefficients a calibration of the detector with a standard gamma-calibration source is performed. With this new technique the energy resolution of neutron-damaged coaxial n-type HPGe-detectors can be improved significantly.

High spin structure in127Xe and125Xe

Excited states of the nuclei127Xe and125Xe have been investigated in the inverse kinematic reactions48Ca(82Se,(3.5)n) at 275 MeV beam energy with the OSIRIS multidetector system at the VICKSI-accelerator of the HMI Berlin. The level scheme of127Xe was extended up to a level of tentative spin (51/2−). Two excited bands of 3QP-character were observed. For125Xe these structures were extended towards higher spins. Experimental Routhians of selected bands are presented.

Excited States in the Transitional N=45 Nucleus 85Zr

Excited states in the transitional nucleus85Zr were studied via the fusion evaporation reaction56Fe(35Cl,αpn)85Zr at 120 MeV. A level scheme reaching up to probable spins of (33/2+) at 6.2 MeV and (27/2−) at 4.9 MeV was established and compared to neighbouring nuclei.

High spin states in147Tb

The level scheme of147Tb has been extended to 116 levels and 198 transitions in two experiments with the OSIRIS Compton suppressed detector array at the HMI Berlin with the reactions122Sn(31P, 6n)147Tb at 160 MeV and120Sn(31P, 4n)147Tb at 152 MeV. Evidence for a new high spin isomer atE=7664.1 keV with a life-time of the order of 2 ns has been found.

Crossing of the high-spin members of the and multiplets in

The nucleus was studied through two experiments, at MeV and at MeV. From measured angular distributions of the scattered deuterons and from a DCO analysis of the observed -rays, spin-parity assignments and information about the structure of the states were obtained. We discuss only the results for the high-spin members of the and multiplets and show that a crossing of the and states from the two multiplets appears due to the interaction of the quadrupole moments of the and core states with the quadrupole moment of the hole.

Analogous negative parity spectra of125Xe and127Xe

The low spin states of the nucleus127Xe have been investigated with the (α, 2n) reaction by means of in-beam-γ-spectroscopy, using theosiris-cube-spectrometer at the FNTandem accelerator facility of the University of Cologne. In the negative parity system, four excited states for each of the spins 11/2−.15/2− and two 5/2−.9/2− — states could be established at excitation energies up to ≈ 1MeV above the Yrast line. With this new data, we are able to compare the non-Yrast states and their decay properties to the corresponding states of125Xe, which had been studied with similar methods in Cologne. The almost one-to-one correspondence between the states of these neighboring neutron-odd nuclei is a clear indication that their excitations at low spin remain collective well above the Yrast line.

High spin states in148Tb

The level scheme of148Tb has been extended to an excitation energyEx=14.0 MeV and a spinI≈ 38ħ in two experiments with the OSIRIS Comptom suppressed detector array at the HMI Berlin using the reactions122Sn(31P,5n)148Tb at 160 MeV and120Sn(31P,3n)148Tb at 152 MeV.

High spin states in145Gd

The data from two experiments with heavy ion induced reactions at the OSIRIS Compton suppressed Ge detector array has been analyzed to study high spin states in145Gd. The level scheme of145Gd has been extended up to an excitation energy of 12 MeV and an estimated spin of 25 ħ. No evidence for high spin isomers was found.