I. Deloncle

High-spin states with seniorityv=4, 5, and 6 in119–126Sn

The 119-126Sn nuclei have been produced as fission fragments in two reactions induced by heavy ions: 12C+238U at 90 MeV bombarding energy, 18O+208Pb at 85 MeV. Their level schemes have been built from gamma rays detected using the Euroball array. High-spin states located above the long-lived isomeric states of the even- and odd-A 120-126Sn nuclei have been identified. Moreover isomeric states lying around 4.5 MeV have been established in 120,122,124,126Sn from the delayed coincidences between the fission fragment detector SAPhIR and the Euroball array. The states located above 3-MeV excitation energy are ascribed to several broken pairs of neutrons occupying the nu h11/2 orbit. The maximum value of angular momentum available in such a high-j shell, i.e. for mid-occupation and the breaking of the three neutron pairs, has been identified. This process is observed for the first time in spherical nuclei.

Measurements of nuclear

{gamma}-ray production cross sections have been measured in proton irradiations of N, Ne, and Si and {alpha}-particle irradiations of N and Ne. In the same experiment we extracted also line shapes for strong {gamma}-ray lines of {sup 16}O produced in proton and {alpha}-particle irradiations of O. For the measurements gas targets were used for N, O, and Ne and a thick foil for Si. All targets were of natural isotopic composition. Beams in the energy range up to 26 MeV for protons and 39 MeV for {alpha} particles were delivered by the Institut de Physique Nucleaire-Orsay tandem accelerator. The {gamma} rays were detected with four high-purity Ge detectors in the angular range 30 deg. to 135 deg. We extracted 36 cross-section excitation functions for proton reactions and 14 for {alpha}-particle reactions. For the majority of the excitation functions no other data exist to our knowledge. Where comparison with existing data was possible, usually a very good agreement was found. It is shown that these data are very interesting for constraining nuclear reaction models. In particular, the agreement of cross section calculations in the nuclear reaction code talys with the measured data could be improved by adjusting the coupling schemes ofmorexa0» collective levels in the target nuclei {sup 14}N, {sup 20,22}Ne, and {sup 28}Si. The importance of these results for the modeling of nuclear {gamma}-ray line emission in astrophysical sites is discussed.«xa0less

\gamma

Five N=82 isotones have been produced in two fusion-fission reactions and their gamma-rays studied with the Euroball array. The high-spin states of 139La have been identified for the first time, while the high-spin yrast and near-to-yrast structures of the four others have been greatly extended. From angular correlation analysis,spin values have been assigned to some states of 136Xe and 137Cs. Several cascades involving gamma-rays of 139La have been found to be delayed, they deexcite an isomeric state with T1/2= 315(35) ns located at 1800-keV excitation energy. The excited states of these five N=82 isotones are expected to be due to various proton excitations involving the three high-j subshells located above the Z=50 shell closure. This is confirmed by the results of shell-model calculations performed in this work. In addition, high-spin states corresponding to the excitation of the neutron core have been unambiguously identified in 136Xe, 137Cs, and 138Ba.

-ray line emission in interactions of protons and

In order to perform half-life measurements at Alto, we developed a fast-timing setup using fast scintillators : LaBr3. The main components of our setup and their characteristics (timing properties) are presented. The resulting time resolution, obtained after optimization, and measured off-line with radioactive sources is discussed. This set-up was tested on-line by measuring using the slope method half-lives of 137–139Cs levels fed by the β− decay of 137–139Xe. The neutron-rich Xe nuclei were produced by 238U photofission using, at low intensity, the electron beam and the line of the future facility ALTO. Our results show the ability of such a fast-timing system to measure half-lives lower than the total time resolution. Off-line and on-line results are discussed.

\alpha

The high-spin states of the two neutron-rich nuclei

particles with N, O, Ne and Si.

{}^{88}

High-spin structures of five N = 82 isotopes: 54 136 Xe, 55 137 Cs, 56 138 Ba, 57 139 La, and 58 140 Ce

Kr

Fast timing: Lifetime measurements with LaBr3 scintillators

{}_{52}

High-spin structures of3688Kr52and3789Rb52: Evolution from collective to single-particle behavior

and

High-spin structures of55136Cs81

{}^{89}