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A new multiparameter experiment on ternary fission of 252Cf has recently been successfully performed by using the CODIS2 detector system and two GSI segmented Super Clover Ge γ-ray detectors. The experimental setup and the main subjects of interest are briefly described. [ABSTRACT FROM AUTHOR]

The 137I nucleus, populated in the spontaneous fission of 248Cm has been studied by means of prompt γ-ray spectroscopy using the EUROGAM2 array. Medium-spin yrast excitations in 137I were observed for the first time. The experimental level scheme is compared to the shell model calculation with modified Kuo-Herling interaction. The theoretical predictions differ significantly from the experimental results, indicating that the excitation pattern in 137I deviates significantly from the shell model scheme. [ABSTRACT FROM AUTHOR]

Neutron-rich, 88-94Kr nuclei, populated in spontaneous fission of 248Cm, have been studied with EUROGAM 2, by measuring prompt γ-rays. Many new excited states in even-even Kr isotopes have been identified. For the first time spins and parities were determined experimentally in these nuclei. Our results indicate that the quadrupole deformation of Kr isotopes will appear only above N = 58, as observed in Sr and Zr nuclei. The newly found 3- level at 1506.4 keV in 90Kr suggests the exsistence of a new region of increased octupole correlations, probably associated with the ν( d5/2 h11/2) pair of Δ l = Δ j = 3 orbitals. [ABSTRACT FROM AUTHOR]

Excited states in the neutron-rich, N=84 nuclei 134Sn, 136Te and 138Xe, populated in the spontaneous fission of 248Cm, were studied to medium spins using the EUROGAM2 array. OXBASH code calculations support the experimental identification of maximum aligned configurations in these isotopes. Empirical shell model calculations agree with the proposed excitation energy of the neutron h9/2 excitation in the 132Sn region. A discrepancy between the observed and calculated excitation energy of the Iπ= 12+ level in 136Te indicates possible admixtures of collective excitations in this nucleus. Clear signs of collective excitations are observed in 138Xe. [ABSTRACT FROM AUTHOR]

A γ-γ coincidence technique has been developed for g-factor measurements of short-lived nuclear states. The method involves γ-detection in 4 π geometry as well as transient magnetic fields and the recoil-distance technique. A first experiment was performed for the isotopeYb produced in the reactionNi(Mo, 4 n) at 430 MeV beam energy. The value g=− 0.23(31) of the 14 yrast state, which is compatible with zero, establishes the vi quasiparticle structure to be responsible for the first backbend. A mean g-factor for low spin states around the 4 state, g=+0.48(26) was also derived as well as lifetimes for yrast states up to I=8. [ABSTRACT FROM AUTHOR]

Excited levels in 141Xe, populated in spontaneous fission of 248Cm, were studied by means of prompt γ-ray spectroscopy, using the EUROGAMM2 array. Level scheme of 141Xe obtained in this work shows patterns characteristic of simplex symmetry with s = + i and s = −i bands present but low value of D 0 moment indicates that octupole correlations in Xe isotopes are systematically lower than in Ba nuclei. [ABSTRACT FROM AUTHOR]

Excited levels in 139Cs, populated in spontaneous fission of 248Cm, have been studied by means of prompt gamma spectroscopy, using the EUROGAMM 2 array. New level scheme of 139Cs, different from the one proposed recently, has been established. To confirm the new scheme, additional study of 139Cs has been performed, where γ-rays following β-decay of 139Xe to 139Cs have been measured at the mass separator OSIRIS. [ABSTRACT FROM AUTHOR]

Excited levels in 133Sn and 134Sb, populated in spontaneous fission of 248Cm, were studied by means of prompt-γ spectroscopy, using the EUROGAM 2 multidetector array. The neutron i13/2 single-particle energy has been determined for the first time in the 132Sn region. The energy of the h9/2 neutron level, proposed previously, has been confirmed. [ABSTRACT FROM AUTHOR]

Neutron-rich, N=84 nuclei from the 132Sn region, populated in spontaneous fission of 248Cm, have been studied with EUROGAM 2. Excited states and their spins and parities in the 136Te nucleus were established up to 17ħ. OXBASH code calculations support the experimental identification of maximum aligned configurations in 136Te. Empirical shell model calculations for the Iπ= 14+ level in 136Te indicate that the adopted mass of the 134Te nucleus should be lowered by 200(80) keV. [ABSTRACT FROM AUTHOR]

The very neutron-rich nucleus 138Te produced in the spontaneous fission of 248Cm has been investigated using the EUROGAM II γ-ray multidetector array. The excited states of 138Te observed for the first time indicate that the region of ground state deformation beyond the doubly magic nucleus 132Sn has yet not been reached. [ABSTRACT FROM AUTHOR]

Prompt γ-ray cascades in neutron-rich nuclei around doubly-magic Sn have been studied using a Cm fission source. Yrast states located in the N = 82 isotones Te and I are interpreted as valence proton and neutron particle-hole core excitations with the help of shell model calculations employing empirical nucleon-nucleon interactions from both Sn and Pb regions. [ABSTRACT FROM AUTHOR]

By analysis of fission product γ-ray data measured at Eurogam II using a 248Cm source, yrast levels up to about 2 MeV in the N=84 three-particle nucleus 135Sb have been identified. These levels are interpreted as π g7/2ν f7/2 2 and π g7/2ν f7/2h9/2 states with the help of shell model calculations using empirical nucleon-nucleon interactions. [ABSTRACT FROM AUTHOR]

Abstract: The ground-state structure of the near-drip-line nucleus 23O has been investigated in a one-neutron Coulomb breakup reaction. Differential cross sections for electromagnetic excitation of 23O projectiles (422 MeV/nucleon) incident on a lead target have been obtained from the measurement of the momenta of all breakup products including γ rays. The analysis of the deduced dipole-transition probability into the continuum infers a ground state configuration with a spectroscopic factor of 0.77(10) and thus a ground-state spin , resolving earlier conflicting experimental findings. Final-state interaction is of significant influence, an effective reduced scattering length for low-energy neutron scattering could be derived from the data. [Copyright &y& Elsevier]

Coulomb breakup of unstable neutron-rich carbon isotopes 15,17C has been studied at energies around ∼500–600 MeV/nucleon. Non-resonant low-lying dipole strength is observed in these isotopes which can be explained by a direct breakup mechanism. In addition to the decay neutron from excited projectile, γ-rays emitted from excited fragments after Coulomb breakup are measured in coincidence, giving access to quantitative spectroscopic information. The spectroscopic factor deduced for a valence neutron occupying the s1/2 level in the 15C ground state is consistent with that obtained earlier from (d,p) transfer reactions. The analysis for Coulomb breakup of 17C shows that most of the cross section yields the 16C core in excited states. The predominant ground-state configuration of 17C is found to be 16C(2+)⊗νs,d. [Copyright &y& Elsevier]

Coulomb break up of the neutron-rich 15,17C and 17–22O isotopes has been studied experimentally using secondary beams at energies of 500–600 MeV/u. A comparison between differential cross sections, dσ/dE*, with that obtained from a binary model shows that the main ground-state configuration of 15C is 14C(0+)⊗νS1/2 as expected. For 17C, our preliminary data analysis reveals that the predominant (∼64%) configuration of the ground state is 16C(2+)⊗νs,d. For 17–22O, the low-lying E1 strength amounts up to about 12% of the energy weighted sum rule strength depending on neutron number. The energy weighted E1 strength (integrated up to 15 MeV excitation energy) increases up to 20O then decreases for 21,22O. These data are compared to a shell model calculation. [Copyright &y& Elsevier]