A. Kuhnert

Level spin and moments of inertia in superdeformed nuclei near A = 194

Abstract Experimental transition energies in the superdeformed (SD) bands near A = 190 are least-squares fit to rotational model formulae in order to extract level spin. The data set includes 16 SD bands, which show no evidence of either irregular behavior near the bottom of the bands or abrupt angular momentum alignment at low ħw . The 9 transitions lowest in energy in each band are well described by the formulae. The fitted spin of the final state in the γ-ray cascade is within ±0.1 ħ of an integer or half-odd integer for 13 of the bands. The weight of the evidence suggests that meaningful level spins corresponding to these transitions can be inferred. The moment of inertia at ω = 0 is correlated, with J = 88.3(5) ħ 2 / MeV and J = 93.4(5) ħ 2 / MeV for the strong and weak bands, respectively.

Levels, lifetimes and g-factors in 198Po and 200Po

Abstract 198,200 Po nuclei have been studied by in-beam gamma-ray spectroscopy with the 182,184 W( 20 Ne, 4n) reactions. In both nuclei 8 + , 11 − and 12 + isomers have been observed, and their lifetimes and g -factors were measured. The low-spin states show signs of a collective structure, while at higher spins very pure neutron and proton states occur with very little mutual interaction.

Oblate collectivity in sup 197 Pb

Evidence for collective behavior in the high-spin region of lead nuclei is provided by the observation of two collective structures in {sup 197}Pb. One of these bands is interpreted as an oblate collective structure built on oblate proton and possibly neutron states. A second more irregular band is suggested to be most likely a triaxial rotational band. Neutron and proton configurations for these bands are suggested from the results of quasiparticle Routhians and total Routhians surface calculations. A partial level scheme up to {ital I}{approx}69/2 and {ital E}{sub {ital x}}{approx}8 MeV is presented.

ONSET OF COLLECTIVITY IN NEUTRON-DEFICIENT PO-196,PO-198

We have studied via in-beam gamma-ray spectroscopy Po-196 and Po-198, which are the first neutron-deficient Po isotopes to exhibit a collective low-lying structure. The ratios of yrast state energi ...

Superdeformed bands in195Tl

Two superdeformed (SD) bands have been found and assigned to195Tl on the basis of excitation function and cross bombardment results. The two bands are almost identical in transition energies to those observed in193Tl. They are signature partners with a splitting, presumably due to the proton i13/2 (Ω=5/2) orbital, characteristic of all known SD bands in the thallium isotopes. Their alignments relative to the193Tl bands were found to be zero.

Nuclear structure study of the neutron deficient cadmium isotopes100, 101, 102Cd

The neutron-deficient nuclei100,101Cd were identified for the first time in — beam following the reactions58Ni +46,48Ti and58Ni +50Cr at 230 MeV and 245 MeV bombarding energy of the58Ni beams. Theγ-decay of the isotopes100,101,102Cd was studied inpγ, ppγ,nγ, nnγ, andnγγ prompt and delayed coincidence spectra. Isomers were found with spin and half life {ie1-01}=8+, T1/2=52(5) ns in100Cd, {ie1-02}=(19/2+), T1/2=4.6(4) ns in101Cd and {ie1-03}=8+, T1/2=56(4) ns in102Cd. In a PAD experiment theg-factor of the {ie1-04}=8+ isomer in100Cd was measured to be g=1.24(6). Using the reaction36Ar +70Ge at 135 MeV energy of the36Ar beam, theg-factor and the quadrupole moment of the {ie1-05}=8+ isomer in102Cd were measured to be g=1.29(3) and Q=87(10) fm2, respectively. The spectroscopic results are discussed within a shell model approach using a100Sn core, which accounts well for the electromagnetic properties of the proton aligned isomers. The structure of the spherical neutron states, dominated by the close lying vd5/2, g7/2 orbitals, and the gradually developing quadrupole collectivity are reproduced by the shell model calculations.

HIGH-K BANDS IN THE YB-166 REGION

High-[ital K] bands have been observed in the [sup 166,167,168]Yb isotopes following the [sup 124]Sn([sup 48]Ca,[ital xn][gamma]) reaction. The [nu][ital h][sub 11/2] band in [sup 167]Yb has been extended to higher spins. The high-[ital K] bands in the even-even isotopes were observed for the first time and show very high [ital B]([ital M]1)/[ital B]([ital E]2) ratios. Configuration assignments for the new bands are proposed. The results are interpreted within the Tilted Cranking model.

High-[ital K] bands in the [sup 166]Yb region

High-[ital K] bands have been observed in the [sup 166,167,168]Yb isotopes following the [sup 124]Sn([sup 48]Ca,[ital xn][gamma]) reaction. The [nu][ital h][sub 11/2] band in [sup 167]Yb has been extended to higher spins. The high-[ital K] bands in the even-even isotopes were observed for the first time and show very high [ital B]([ital M]1)/[ital B]([ital E]2) ratios. Configuration assignments for the new bands are proposed. The results are interpreted within the Tilted Cranking model.

SUPERDEFORMATION IN AU-191

A superdeformed band has been observed for the first time in an Au isotope. The reaction used was B-11 + W-186, demonstrating that very light ions can be used to populate superdeformed (SD) bands a ...

LIFETIMES OF SUPERDEFORMED STATES IN 194PB

Lifetimes of members of the superdeformed band in 194Pb were measured by the Doppler-shift attenuation method. Quadrupole moments around 20 eb that are constant over the whole frequency range were derived. The results rule out large centrifugal stretching effects.