Low spin structure of128Xe

The low spin structure of¹²⁸Xe has been studied by means of the (α,n) reaction using beam energies near the Coulomb barrier. An extended level scheme with spins I≤10? and many new spin and parity assignments could be established. The results point to the completeness of the reaction at low spins and excitation energies below 2.5 MeV.     

Average spins of primary fission fragments

The average spins at which final fragments are formed after fission following fusion of ¹⁹F with ¹⁹⁷Au have been measured directly from spectroscopic studies of discrete γ-ray lines. The final fragment spins can be translated into average spins at which primary fragments are formed by adding changes due to statistical γ-ray emission and post-fission neutron emission. The average primary fragment spins show marked variations with fragment mass. Possible causes for the structure are discussed within the framework of the statistical scission model of heavy-ion induced fission.     

Evidence for wobbling excitation in 161Lu

High-spin states in ¹⁶¹Lu were investigated using the EUROBALL spectrometer. A previously known triaxial superdeformed band has been extended to higher spins and a new band with similar characteristics has been discovered. Comparison to systematically occurring wobbling bands in Lu isotopes strongly suggests that these two bands represent the n_w = 0 and 1 wobbling excitations in ¹⁶¹Lu.     

Nuclear level structure of99Tc

The gamma rays of⁹⁹Tc excited through negatron decay of⁹⁹Mo have been studied by internal conversion spectroscopy, using a high resolution double focusing beta-ray spectrometer. Conversion electrons were observed for all transitions reported before. In addition a new gamma ray of energy 989.37±1.02 keV could be identified and ascribed for the first time to the decay of⁹⁹Mo. Gamma-ray energies have been determined with high precision. Multipolarity data, obtained from the measurements of absolute or ratio of conversion coefficients of gamma rays, were utilized for assigning possible spins and parities to the levels of⁹⁹Tc. From our present data combined with other studies spins and parities; 7/2+, 1/2?, 5/2+, 3/2?, 3/2+ and 5/2? have been given to the 140, 142, 181, 514, 922 and 1131 keV levels respectively. The experimental level scheme is discussed in terms of theoretical predictions.     

Gamma-ray spectroscopy of62Cu

A spectroscopy study has been made of the⁶²Ni(p,nγ)⁶²Cu reaction, allowing levels in⁶²Cu to be investigated up toE _x=1.843 MeV. Ten new levels and eleven spins are given.     

Antiferromagnetic interactions between localized states in amorphous germanium

The temperature dependence of the magnetic susceptibility (300 → 1.6°K) and ESR (300 → 6°K) of amorphous germanium have been determined. There is a temperature dependent paramagnetic term to the magnetic susceptibility due to a density of localized unpaired spins (dangling bonds) of 10¹⁹ spins/cm³. There is an antiferromagnetic interaction between at least some of these localized unpaired spins with an exchange energy estimated by various models to be on the order of a degree Kelvin.     

New yrast excited states of the N = 84 nucleus 142Ce observed in deep inelastic reactions

Excited states of ¹⁴²Ce, populated in deep inelastic reactions of ⁸²Se projectiles bombarding ¹³⁹La target, have been studied up to medium spins using in-beam γ spectroscopy techniques. Three new levels have been identified at 2625, 2995, 3834 keV, and assigned as 8⁺, 9^(-) and 11^(-), respectively. These new yrast states follow closely the level systematics of the even mass N = 84 isotones. Their strctures have been discussed with the help of empirical shell model calculations. Received: 2 November 2001 / Accepted: 15 January 2002     

Exotic nuclei produced by heavy-ions induced fission

About thirty nuclei in theA≈100 mass region have been produced as fission fragments following the fusion-evaporation reactions^28,30Si+¹⁷⁶Yb at 145 MeV bombarding energy. These nuclei have been individually identified from their γ-ray cascades detected with the Eurogam2 array. The level schemes of several stable or neutron-rich nuclei have been extended to higher spins. From cross coincidences between transitions in complementary fragments, γ-rays de-exciting high-spin states of new isotopes can be identified and some aspects of the fission mechanism can be analyzed.     

High-spin levels in 147Tb

The high-spin states of ¹⁴⁷Tb have been studied with regard to their spins. The data were obtained by in-beam γ-ray spectroscopy using the reaction ¹²⁰Sn(³¹P,4n)¹⁴⁷Tb at 152 MeV performed at the Osiris spectrometer in Berlin. We obtained multipole mixing ratios for 60 transitions, and level spins up to 67/2ħ are introduced. Received: 30 March 1998     

High-spin spectroscopy of168Hf

The nucleus¹⁶⁸Hf was studied up to spin (38⁺) in the yrast band and to spins (41^?) and (38^?) in the lowest two negative-parity bands. The onset of a proton alignment (h_9/2 or i_13/2 quasiparticles) is observed in these three bands for the highest transitions. A new band with even spins and negative parity was found. The interaction strength between the ground-state band and theAB band is measured.     

Spectroscopic study of the 54Fe(16O,pn)68As reaction

Low and high states of the doubly odd nucleus ⁶⁸As have been studied through in-beam γ spectroscopy via the ⁵⁴Fe(¹⁶O, np) reaction. A new level scheme for the ⁶⁸As nucleus was determined on the basis of the neutron-γ and neutron-γγ coincidences,excitation functions, angular distributions and linear polarisation. New spins, parities and γ-decay properties were established.     

High-spin structure of yrast-band in 78Kr

Lifetime of levels up to 22⁺, have been measured in ⁷⁸Kr and an oblate shape is assigned to the ground state using the CSM and the configuration dependent shell correction calculations. Calculations further show that ⁷⁸Kr is highly γ-soft nucleus. The experimental Q _t values coupled with theoretical calculations indicate an oblate shape for ⁷⁸Kr at low spins and triaxial shape at higher spins     

Level structure of 99Rh at high spins

High spins states in ⁹⁹Rh were populated via the ⁶⁶Zn(³⁷Cl, 2p2n)⁹⁹Rh reaction at an incident beam energy of 130 MeV. Seventeen new transitions have been observed in the present study and the level scheme has now been extended up to a spin of J∼ 25ħ and an excitation energy of about E _x∼ 10 MeV. The observation of a positive parity E2 cascade based on the 9/2⁺ isomeric level is suggestive of collective behaviour in this nucleus up to high spins. Spherical shell model (within restricted model space) and Cranked shell model calculations were performed to obtain an insight into the observed level structure. The new collective band observed up to a spin of J∼ 25ħ is suggested to be based on (πg _9/2 ³) ⊗ (νg _7/2 ²) quasi-particle excitations. Received: 12 July 1999 / Revised version: 14 September 1999     

Levels of 41Sc from the 40Ca(p,p)40Ca reaction

Excitation functions have been measured for ⁴⁰Ca(p, p)⁴⁰Ca, in the energy range from E_p = 2.35 to 4.85 MeV at four angles. The R-matrix formalism for multilevel cross sections was used to analyse the data; spins, parities, proton widths and reduced widths were extracted for thirty levels. Several new spin values have been deduced. A detailed comparison of the levels in the mirror system ⁴¹Ca?⁴¹Sc is given.     

New isomers and states of (πg 9/2 ⊗vg 9/2) parentage in84Rb

Excited states in the doubly-odd nucleus⁸⁴Rb have mainly been studied via the (α,n) reaction by means of in- beam γ-ray spectroscopy. Two new isomers have been found, a 5^? level at 467.1 keV and a 5⁽⁺⁾ level at 544.2 keV with half-lives of 9(2) ns. and 11(1) ns, respectively. On top of the 5⁽⁺⁾ isomer a level sequence with increasing spins up to 10 ? and probably positive parity has been identified. These states are ascribed to the configuration (πg_9/2?vg_9/2).     

Shape changes in189Au at high spins

The level scheme of¹⁸⁹Au has been extended to high spins. Decoupled, strongly coupled as well as vibrational bands have been found indicating shape coexistence in this nucleus.     

Gamma-ray spectroscopy of the nucleus 139Ce

Gamma-ray coincidence techniques are used to determine new level structures in the N = 81 nucleus ¹³⁹Ce, at low spins and excitation energies with the ¹³⁹La(p, nγ) reaction at 5.0 and 6.0MeV incident energy, and at high spins with the ¹³⁰Te(¹²C, 3nγ) reaction at 50.5MeV, respectively. Lifetime determinations are also made in the (p, nγ) reaction with the centroid DSA method. The observed level structures are discussed by comparison with existing calculations and with those in the neighbouring nucleus ¹⁴⁰Ce.     

Reduced transition probabilities for high-spin states in 232Th

The lifetimes and reduced transition probabilities for spins 6⁺ ? 18⁺ in the ground-state rotational band of ²³²Th have been measured by recoil-distance, Doppler-broadened lineshape, and multiple Coulomb excitation methods using ⁸⁴Kr and ¹³⁶Xe projectiles. Within the limits of experimental uncertainty, transition probabilities from all of the methods are consistent with those of a good rotor for spins 6⁺ ? 18⁺. The descrepancy with the prediction of simple β-band mixing and centrifugal stretching models is discussed.     

High-spin levels based on the 11/2- isomer in 135Ba

High-spin states in the ¹³⁵Ba nucleus have been studied with the reaction ¹³⁰Te(⁹Be, 4n) at a beam energy of 45 MeV. The level scheme based on the h _11/2 isomer has been expanded with spins up to 35/2 ℏ. At low spins, the yrast collective structure built on the ν h _11/2 ^-1 multiplet may show a transitional shape with γ > 30^° according to the systematical behavior observed in neighboring nuclei as well as the calculations of the triaxial rotor-plus-particle model. The configurations for several high-spin states have been discussed from a systematical comparison with neighboring isotones.