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The electromagnetic decay properties of high spin states in 52Mn have been studied through various experiments with the GASP and EUROBALL arrays plus the ISIS charged-particle detector, the Neutron-Wall and the Recoil Filter Detector. From 7-7-particles coincidence measurements, spins and parities of these states have been determined and using the Doppler-shift attenuation method the mean life of some of these states have been determined. These results are compared with large scale shell-model calculations in the full fp shell.

Two peat columns from Tunguska (Siberia) were analysed for pollen, spores, charcoal, trace elements and γ-emitters in order to identify the fingerprints of the impact of a still unidentified cosmic body (TCB), which occurred in the summer of 1908, and the level of environmental pollution in a background area of central Siberia. Peat layers were subject to non-destructive γ-ray spectrometry to derive radiochronology by the excess 210Pb method. The age-to-depth relationship was crosschecked by using both 1963 horizon of 137Cs associated to maximum global fallout deposition and palynological data profiles. Vertical distributions of trace elements in the peat columns were obtained by PIXE multielemental analysis allowing determination of the levels of environmental contamination in a background region of the Siberian taiga. The association of heavy metals such as Ni, Co and Cu in the profiles suggests the connection of the area with mining and metal smelting activity in the north of the region through atmospheric circulation. As concerns global scale contamination, the inventory of the artificial radionuclide 137Cs (4.6 kBq m− 2) shows a value typical of remote slightly contaminated areas resulting from global scale redistribution of radioactive fallout from Cold War nuclear weapon testing. The atmospheric inventory of the natural radionuclide 210Pb, for which a mean annual flux of 200 Bq m− 2 yr− 1 has been calculated, is typical of continental regions. The influence of Tunguska Cosmic Body in the peat is recognizable by a large discontinuity in the palynological profile of the peat monolith at a depth coinciding with the 1908 layer as determined by the 210Pb technique, showing a large peak of total pollen counting attributed to the impact of the shockwave on the area in which huge tree stands were destroyed. Following the event, tree pollen concentration decreases abruptly showing the temporary inception of a mire environment with an increase of Sphagnum spore concentrations. Results of elemental analysis so far available do not show anomalies in the concentration profiles at depths coinciding with the Tunguska event layer indicating the need for pre-concentration technique enabling the detection of element associations typical of extraterrestrial materials.

Analysis of thirteen medicinal plants of various biological activities commonly used in South-western Nigeria was carried out using PIXE technique. Nine of these plants are anti-cancer while four are antimicrobial. PIXE measurements were carried out using collimated proton beams delivered by the 2. 5 MV AN 2000 Van de Graaff accelerator at the Istituto Nazionale di Fisica Nucleare (INFN), (LNL) Legnaro, (Padova), Italy. The results showed the presence of twenty three different elements in the plants and none of them contains any toxic heavy metals. Only Chenopodium ambrosioides showed detectable levels of selenium which is considered important in cancer prevention.

PIXE technique was employed in the determination of the major, minor and trace elemental concentrations in finger-nails of 62 healthy young adults (30 females and 32 males), aged between 20 and 37 years. The elemental concentrations in the nails of the analyzed population provide good reference data set for further health studies. The PIXE measurements were carried out using 1.8 MeV collimated proton beam from the 2.5 MV AN-2000 Van de Graaff accelerator at INFN, LNL, Legnaro (Padova), Italy. The results show the presence of twenty elements. Their metabolic roles in humans are presented and discussed. The comparison of our results with those of other authors are also presented.

Excited states of the neutron deficient Ag-101 nucleus have been investigated via the Cr-50(Ni-58, 3rho1alpha) heavy-ion induced reaction at 261 meV by use of in-beam spectroscopic methods. On the basis of the measured gammagamma-cincidence relations and angular distribution ratios high-spin bands have been extended up to I-pi = 35/2(+), 45/2((-)) and (49/2(-)). The negative parity states at the highest energy have been interpreted as terminating non-collective oblate states in the framework of the Nilsson-Strutinsky cranking formalism.

The reactions 16O(7Li, 2n) and 16O(7Li, np) populating 21Na and 21Ne have been studied at E L=27 MeV using the GASP γ-detector array. The level schemes for 21Na and 21Ne have been extended to higher spin. The population of the bands with K=3/2 and 1/2, forming parity doublets, are compared. Preferential E1 decay between bands of opposite parity is observed in agreement with the octupole scenario. The structure of these bands can be interpreted as consisting of an instrinsic asymmetric (4He + 16O) structure with octupole deformation.

The reactions 16O(7Li, 2n) and 16O(7Li, np) populating 21Na and 21Ne have been studied at EL = 27 MeV using the GASP γ-detector array. The level scheme for 21Na and 21Ne has been extended to higher excitation energy. Spins and parities of the observed levels are assigned tentatively supporting the identification of opposite parity structures connected by strong dipole transitions. The structure of these bands is interpreted as based on a reflection asymmetric cluster structure.

In the framework of the European program to define a second generation Radioactive Ion Beam facility, LNL are proposing the construction in the next five–seven years of a specialized national facility for RIB originated by fission fragments produced by secondary neutrons. It consists on a two-accelerator ISOL-type facility to provide intense neutron-rich radioactive ion beams of highest quality, in the range of masses between 80 and 160. The conceptual design is based on a high intensity 50 MeV (100 kW) proton linac as driver and on the availability of the heavy-ion accelerator ALPI as post accelerator. The estimated neutron yield is 2×1014 n/s at 0°, high enough to satisfy the demand for an advanced RIB facility. An intense R&D program on different items is actually in progress in collaboration with other Laboratories and University groups and is moving in a European context.

Lifetimes have been determined using the Doppler Shift Attenu- ation Method in the N Z nuclei 46 V and 48 V nuclei, populated with the reaction 28 Si on 24 Mg at 115 MeV and 24 Mg on 28 Si at 100 MeV using Au and Pb backed targets. The coexistence of spherical and deformed states in the middle of the 1f7=2 shell is discussed. The B(E2) and B(M1) reduced rates agree very well with large scale shell model predictions.

DSAM lifetimes have been determined in the middle of 1f7/2 shell for the cross-conjugated nuclei 47 Va nd 49 Cr, populated with the reaction 28 Si on 28 Si at 115 MeV using a Au backed target. B(E2) and B(M1) reduced rates agree very well with large scale shell model predictions. The interplay between spherical and collective structures is discussed.  2001 Elsevier Science B.V. All rights reserved.

Gamma ray transitions de-exciting states in the N = Z nucleus 70Br have been identified for the first time using the GASP and EUROBALL arrays coupled with ancillary detectors. The level scheme of 70Br has been established by means of particle-gated γ-γ and γ-γ-γ coincidences. The Coulomb energy differences between isobaric analogue states in 70Br and 70Se show a deviation from the expected behaviour which could be related to dripline effects.

High-spin states in the nuclei Ga-63 and Ga-65 were studied following the reaction S-32 + Ca-40 at a reaction energy of 125 MeV and using the GASP gamma -ray spectrometer in combination with the ISIS charged-particle detector system. In addition to low-lying negative-parity states with single-particle character, rotational-like cascades built on the 9/2(+) and 19/2(-) states have been observed in both nuclei. Sidebands with negative parity in Ga-63 and positive parity in Ga-65 could be established. The experimental results are compared with Total Routhian Surface calculations which describe the nuclei as moderately deformed (beta (2) approximate to 0.25) and gamma soft at low rotational frequencies. The highest experimentally observed positive-parity state in Ga-65 (41/2(+)) is in good agreement with the calculated crossing of the collective band with a non-collective one terminating at this spin.

High-spin states of the neutron deficient (100)pd nucleus have been investigated via the Cr-50(Ni-58, 4p alpha) and Zn-70(S-36,6n) heavy-ion induced reactions. For the detection of evaporated particles and gamma rays the NORDBALL array equipped with ancillary detectors and the EUROGAM II detector system were utilized. By the use of in-beam spectroscopic methods 89 transitions belonging to (100)pd have been observed, 49 of which were identified for the first time. The level scheme has been extended up to E-X approximate to 16 MeV excitation energy and I approximate to 25h. The experimental results were compared with the predictions of cranked shell model calculations. Maximal spin alignments were found in the (pig(9/2))(12+)(-4) (vd(5/2),g(7/2)(3)h(11/2))(13-) and (pig(9/2)(-3)p(1/2))(11-)(vd(5/2)g(7/2)(3)h(11/2))(13-) configurations. Possible existence of octupole correlations is discussed on the basis of 6 (E 1)lB(E2) values deduced for the decays of high-spin levels in the yrast negative-parity band. (C) 2001 Elsevier Science B.V. All rights reserved.

High-spin states in the neutron-deficient nuclide I-111 have been populated with the fusion reaction Ni-58 + Ni-58 at a beam energy of 210 MeV, in an experiment performed at the Tandem Accelerator of the Laboratori Nazionali di Legnaro. The gamma spectrometer GASP was used in time coincidence with the ISIS Si-ball and the CAMEL recoil mass spectrometer for the positive identification of the nuclide. Gamma transitions and structure details previously attributed to I-111 by Other authors are only partially confirmed. The obtained level scheme includes new rotational bands and a new low lying structure which suggests the presence of octupole correlations at predicted rotational frequency values.

The g factors of the 7 2 + 235 keV isomer in 175W and the 14+ 3746 keV isomer in 176W have been measured by observing the precession of the decay γ-ray angular distribution in an external magnetic field as g 7 2 + , 175 W =−0.187(6) and g(14 + , 176 W )=+0.475(15) . A pure wave function has been assigned to the Kπ=14+ isomer from comparison with predictions based on experimental g factors of deformed single-particle orbitals in this mass region. The value gR=0.27(2) has been deduced for the rotational g factor by using the measured g factor of the 14+ state and the branching ratios in the associated band.

The lifetime andthe γ-decay to the 0+ groundstate of the lowest 3− state in 148Gd has been determined. The reduced strength B(E3, 3− → 0+)=41 (6) W.u. agrees well with the theoretical value from empirical shell model calculations and can be directly compared with the 12+ → 9− two-octupole-phonon → one-octupole-phonon strength obtained in the same Recoil Distance Method lifetime measurement. The results of our search for a three octupole-phonon state built on the (νf 7/2) 6+ 2 state is also reported.

The g-factors of some members of the ground state band and of the 2+ state in the γ-vibrational band have been measured in 160,162,164Dy using the Coulomb Excitation Transient Field technique, induced by 58Ni projectiles at 230, 210 and 217 MeV, respectively. The g-factors in the ground state band are consistent with a constant value, while that of the 2+γ states is about 20% larger in average than those in the ground state band. Results are discussed in the frame of the systematics in this nuclear region.

Excited states of 65Ga and 67Ga nuclei were populated through the 12C(58Ni,αp) and 12C(58Ni,3p) reactions, respectively, and investigated by in-beam γ-ray spectroscopic methods. The NORDBALL array equipped with a charged particle ball and 11 neutron detectors was used to detect the evaporated particles and γ rays. The level schemes of 65,67Ga were constructed on the basis of γγ-coincidence relations up to 8.6 and 10 MeV excitation energy, and Iπ=27/2 and 33/2+ spin and parity, respectively. The structure of 65,67Ga nuclei was described in the interacting boson-fermion plus broken pair model, including quasiproton, quasiproton-two-quasineutron, and three-quasiproton fermion configurations in the boson-fermion basis states. Most of the states were assigned to quasiparticle + phonon and three quasiparticle configurations on the basis of their electromagnetic decay properties.

Excited states in ${}^{52}\mathrm{Fe}$ have been studied up to spin $10\ensuremath{\Elzxh}$ in the reaction ${}^{28}\mathrm{Si}{+}^{28}\mathrm{Si}$ at 115 MeV beam energy by using in-beam $\ensuremath{\gamma}$-ray spectroscopy methods at the GASP array. The excitation energy of the yrast ${10}^{+}$ state is 7.381 MeV, almost 0.5 MeV above the well known ${\ensuremath{\beta}}^{+}$-decaying yrast ${12}^{+}$ state. Experimental upper limits for the $B(E4)$ transition probabilities from the ${12}^{+}$ isomer to the ${8}_{1}^{+}$ and ${8}_{2}^{+}$ states have been determined. The mean lifetimes of five excited states have been measured by using the Doppler shift attenuation method. Complete diagonalizations in the $\mathrm{pf}$ major shell lead to very good agreement with the experimental level scheme and transition probabilities. The lifetime, $\mathrm{log}\mathrm{ft}$ value, branching ratios, and $B(E4)$ values are calculated for the ${12}^{+}$ isomer. The positive parity states are also interpreted in terms of a Nilsson projected method. The structure of the yrast levels of ${}^{52}\mathrm{Fe}$ is compared with those of its cross conjugate ${}^{44}\mathrm{Ti}.$

Excited states of As-68 nucleus were populated through the C-12(Ni-58,pn) reaction and investigated by in-beam gamma-spectroscopic methods. The NORDBALL detector array equipped with charged particle and neutron detectors was used to detect the evaporated particles and gamma-rays. The level scheme of As-68 was constructed on the basis of gamma gamma-coincidence relations up to 6 MeV excitation energy and J(pi) = (15(+)). The structure of the nucleus is discussed in the framework of the interacting boson-fermion-fermion model. The states below 2.3 MeV are described as members of proton-neutron-phonon multiplets. (C) 1998 Elsevier Science B.V.

The g–factor of the 2+ 1 state in 180Pt has been measured by means of an implantation-decay technique in conjunction with the γ-ray detector array GASP, thereby extending the g(2+ 1) systematics for Pt isotopes across the upper part of the valence neutron shell, beginning below mid-shell. Despite the variation in the number of valence neutron holes from 6 to 22, the g-factors remain nearly constant and near 0.7Z/A.

In the neutron deficient isotopes 104,105In lifetimes of high spin states in the range from 0.5 ps to 600 ps have been measured in a coincidence recoil distance Doppler shift (RDDS) experiment. By combining the Doppler shift attenuation (DSA) and RDDS methods at few μm flight distances, the problem of delayed feeding has been avoided and very short lifetimes in the range 0.5–0.8 ps have been determined. Shell model calculations with strong restrictions for the neutron orbitals reveal good agreement with experimental level energies and still fair agreement for most measured B(M1) and B(E2) values.

High spin states in ${}^{104}\mathrm{Sn}$ were identified in the reaction ${}^{58}\mathrm{Ni}{(}^{50}\mathrm{Cr}$, $2p2n)$ at 200 and 205 MeV beam energies. The $\ensuremath{\gamma}$-ray energies, intensities, multipolarities, and lifetimes of high spin states were measured with the GASP spectrometer array in combination with a plunger apparatus by means of the recoil distance Doppler shift method. The deduced level scheme and transition probabilities are compared to the results of large-scale shell model calculations using three independent two-body interactions. The agreement of the level energies is satisfactory, except for a cascade of dipole transitions at high spins. The general good agreement found for $E2$ transition strengths implies a large effective neutron polarization charge. The shell-model calculations do not account for the measured enhanced $E3$ transitions for which a core excited octupole phonon admixture is indicated.

The mean lives of the lowest 9- and 12+ states of146Sm have been measured by means of the RDM. Their (preliminary) values are τm(9-) = 0.97 ± 0.05 ns and τm(12+) = 15 ± 2 ps, respectively. The strengths of the collectiveE3 transitions of the 12+ → 9- → 6+ cascade are compared with the corresponding ones in148Gd.

The high-spin structure of deformedN = Z nuclei inf7/2 shell is presented. The experimental data obtained with the 4π γ-ray spectrometer is compared with large-scale shell model calculations. In odd-odd self-conjugate nuclei, bothT = 0 andT = 1 band-like structures have been observed.

The g -factors and quadrupole moments of the 9 2 − isomeric states in 129,131 Ce have been determined by the TDPAD method. The results are g = −0.185(10) and | Q | = 1.32(13) eb for 129 Ce and g = −0.189(7) and | Q | = 0.92(10) eb for 131 Ce. Firm spin-parity assignments were made on the basis of measured moments. The experimental electromagnetic moments and the level energies in the positive- and negative-parity bands were analysed within the particle-plus-triaxial-rotor model and optimum shape parameters have been established.

Intermediate mass fragments (IMF) and light particles emitted from the Ni-58 + Ni-58 reaction at a beam energy of 375 MeV have been studied. The fragments and light particles were measured in coincidence with 4 pi gamma-ray spectrometer. The Z=6 (C) kinetic energy spectra and the distribution of the final nuclei in coincidence with the emitted C are well described by Hauser-Feshbach calculations extended to many channels. A detailed study of C-Psi and 3 alpha-gamma correlations indicate a strong selectivity of the IMF decay. Our results indicate that the IMF can populate nuclei that are not accessible via multiple light particle (Z

The quadrupole moments of highly deformed bands in ${}^{134,135}\mathrm{Nd}$ and ${}^{131}\mathrm{Ce}$ have been determined using the Doppler-shift attenuation method. The obtained ${Q}_{0}$ values show no clear dependence on the number of occupied $\ensuremath{\nu}{i}_{13/2}$ intruder orbitals. Cranked shell model calculations indicate that the charge-quadrupole moments of the highly deformed bands decrease with increasing spin. The expected increase in deformation induced by the $\ensuremath{\nu}{i}_{13/2}$ orbital in two bands of ${}^{134}\mathrm{Nd}$ is attenuated by a rotation-induced shrinking effect driving the nucleus towards smaller deformation.

Neutron deficient nuclei close to 100Sn have been studied using the NORDBALL Ge-detector array together with ancillary particle detectors. Evaporation residues from the compound nucleus 108Te were identified with charged particle and neutron detectors. In this paper a considerable extension of the level scheme of the nucleus 102Cd is presented. The strongest cascade of the new level scheme reveals an irregular sequence of dipole transitions above Iπ = 10+ extending up to spin 17. A strongly populated rather regular side band consisting of four quadrupole transitions ranging from spin 9 to spin 17 was also discovered. This band was tentatively assigned negative parity. Shell model calculations were performed and a very good agreement with the experimental results was found. The excited states could successfully be interpreted as neutron particle and proton hole excitations with respect to the doubly closed core 50100Sn50.

The structure of Kr-72 has been investigated at GASP through the Ca-40(Ca-40,2 alpha) reaction at a beam energy of 160 MeV using the 4 pi ISIS Si-ball for reaction channel selection. The level scheme has been extended up to an excitation energy of approximate to 8.5 MeV. The spins and parities of the observed levels are assigned tentatively. The observed band shows the predicted change from oblate to prolate shape. The four quasi-particle g(9/2) alignment is found to be significantly delayed in rotational frequency with respect to the heavier Kr isotopes. Such a delay contradicts the predictions of standard mean-field calculations and may reflect either additional correlations in the T = 0 pairing channel or coupling to vibrational degrees of freedom or both. (C) 1997 Elsevier Science B.V. (Less)

High-spin states of the isotopes In-103,In-105,In-107,In-109 have been investigated using in-beam gamma-ray spectroscopic methods. Results from three different experiments are presented. Targets of Fe-54, Cr-50, and Mo-92 were bombarded by a 270 and 261 MeV Ni-58 beam and by a 95 MeV F-19 beam, respectively. Reaction channel separation was achieved with a charged-particle detector array and in the first two experiments also with a 1 pi neutron detector system. As a result of these experiments the level schemes of In-103,In-105,In-107,In-109 were significantly extended. Excited states of these odd-A indium isotopes are discussed within the framework of the nuclear shell model and the hole-core coupling scheme. The systematics of excited states of light odd-A indium isotopes is also discussed. (C) 1997 Elsevier Science B.V.

A 4π Si-ball detector system has been constructed as a trigger device for the γ-ray spectrometer GASP. The construction and operation of the detector is reported, together with a brief description of the electronics and of the data acquisition system used. Results are presented for the 32S + 40Ca reaction at 140 MeV of32S beam energy.

The reaction {sup 58}Ni({sup 28}Si,2n{gamma}) at 90 MeV incident energy has been used to populate the N=Z nucleus {sup 84}Mo. The GASP array was used together with the ISIS Silicon ball, which allowed a subtraction of the charged particle channels in the {gamma}-{gamma} coincidences. The only known transition 2{sub 1}{sup +}{r_arrow}0{sub 1}{sup +} of 443.8 keV in {sup 84}Mo has been found in coincidence with a {gamma} ray of 673.5{plus_minus}0.4 keV which was assigned as the second (4{sub 1}{sup +}{r_arrow}2{sub 1}{sup +}) yrast transition. The behavior of the resulting yrast line indicates that {sup 84}Mo is a transitional nucleus. The correlation between the excitation energies of the 2{sub 1}{sup +} and 4{sub 1}{sup +} levels of the N=Z nuclei reveals a systematic deviation from the average behavior defined by all collective even-even nuclei. {copyright} {ital 1997} {ital The American Physical Society}

The structure of theN=Z nuclei60Zn,62Ga,64Ge, and72Kr has been investigated at GASP. Total Routhian surface (TRS) calculations have been performed for theN=36, 38 and 40 Kr isotones. In the case of72Kr the four quasi-particleg9/2 alignment is observed to be significantly delayed in rotational frequency with respect to the heavier Kr isotopes. Such a delay contradicts the predictions of mean field calculations and may be viewed as the first sign of additional correlations in theT=0 pairing channel.

Excited states of Cd-103 were studied in the reaction Ni-58(Cr-50,4pn)Cd-103. The NORDBALL array with neutron and charged particle detectors was employed for the detection of gamma rays and light evaporated particles. The level scheme of Cd-103 was significantly extended. A strong cascade of E2 transitions connecting negative parity states was found, Shell model calculations were performed and positive parity excited states were interpreted in terms of neutron-particle and proton-hole excitations with respect to the doubly magic N = Z = 50 core. The negative parity band was well reproduced by the total routhian surface calculations. (C) 1997 Elsevier Science B.V.

The stopping power of Nd ions in Pb, in the range from 7 to 35 MeV, has been determined using the γ-ray lineshape analysis of the 696.6 keV transition de-exciting the first 2+ level in 144Nd, populated by Coulomb excitation using a 90 MeV 28Si beam. The data are compared with the most commonly used parameterizations.

The recently discovered regular bands of enhanced $M1$ $\ensuremath{\gamma}$-ray transitions in nearly spherical Pb nuclei have been explained in terms of magnetic rotation. However, the special angular momentum coupling of the nucleons that form magnetic-rotational states has never been tested experimentally. In this paper, we report on the measurement of the $g$ factor of the 2583-keV head of such a band in ${}^{193}\mathrm{Pb}$. The result, $g\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.68(3)$, is the first direct proof of the almost perpendicular coupling of the proton-particle and neutron-hole angular momentum vectors. This coupling results in a large component of the magnetic moment perpendicular to the total nuclear angular momentum, which is required for the occurrence of magnetic rotation.

High-spin states in ${}^{50}$Cr have been investigated with the reaction ${}^{24}\mathrm{Mg}{(}^{32}\mathrm{S},\ensuremath{\alpha}2p)$ at 130 MeV bombarding energy, using the 4$\ensuremath{\pi}$ GASP $\ensuremath{\gamma}$-ray array plus the 4$\ensuremath{\pi}$ charged-particle detector ISIS. The level scheme has been extended up to the 18${}^{+}$ state at 17.954 MeV excitation energy. Several high-spin states which deexcite by emitting high energy $\ensuremath{\gamma}$-rays have been identified. A second backbending is observed at $I=18\ensuremath{\Elzxh}$, well above the 14${}^{+}$ state which exhausts the total spin available in a pure ${(f}_{7/2}{)}^{10}$ configuration.

The ridge structure at {Delta}E{sub {gamma}}={plus_minus}30 keV, observed previously in the reaction 187 MeV {sup 37}Cl + {sup 120}Sn and attributed to an hyperdeformed nuclear shape, has been studied in a high statistics proton-{gamma} coincidence experiment. The presence of the ridge is confirmed but it is correlated to a set of {gamma}-ray energies different from those proposed in earlier works. Some discrete transitions associated with this structure, which accounts for only {approximately}3{times}10{sup {minus}5} of the fusion evaporation cross section, are proposed. {copyright} {ital 1997} {ital The American Physical Society}

Using the (18O,5n) 163Er reaction a multitude of rotational bands have been established with firm spin and parity assignments in 163Er. In 17 out of 24 band crossings E2 cross-band transitions have been observed. The interaction strength varies between ∼ 1 and ∼ 50 keV with many of the values in the range 10–15 keV. These interactions sample a variety of the lowest (multi) -quasiparticle configurations. For some bands, in particular those with high K-values, the configurations can be established rather well. Quite complicated changes in the wavefunctions must occur at these crossings, and to explain the observed interaction strengths coupling to various vibrational degrees of freedom, in addition to possible residual neutron-proton interactions, may be needed.

The present status of experimental approach to 100Sn in the spectroscopy of excited states is landmarked by the Tz=3/2 nuclei between 95Pd and 101In and the Tz=1 nuclei 94Pd and 98Cd. The detection limits with Pre-EUROBALL γ-arrays and ancillary detectors are below the 10−5 level of the total fusion- evaporation residue cross section. A large scale shell model analysis of the existing data reveals the shell structure at 100Sn, which shows a remarkable similarity to 56Ni. Evidence for an increasing proton-neutron interaction in approaching the N=Z line is deduced from high spin isomers and spherical yrast lines. The effective E2 operator for protons and neutrons and implications for a low lying particle-hole (ph) E2 excitation in 100Sn are discussed.

The structure of Sn-105 has been investigated through the Cr-50(Ni-58,2pn) reaction at a beam energy of 210 MeV. In addition to an extension of the spherical level scheme a regular sequence of dipole transitions has been found. The states of the dipole band are suggested to be built on a neutron hf(11/2)(2) excitation coupled to proton particle-hole states, which polarize the core to a slightly prolate shape. The experimental results are in agreement with the prediction of tilted axis cranking calculations, which satisfactorily explain the properties of the band.

Excited states of Cd-101 were studied in the reaction Ni-58(Cr-50,2p alpha n)Cd-101. The NORDBALL array with a Neutron Wall and a Silicon Ball was employed for the detection of gamma-rays and evaporated particles, The level scheme of Cd-101 was significantly extended, Shell-model calculations were performed and the excited states were interpreted in terms of neutron particle and proton hole excitations with respect to the doubly magic N = Z = 50 core.

The high-spin structure of 104Cd has been studied through the 50Cr(58Ni,4p) reaction at a beam energy of 220 MeV. The level scheme has been extended up to an excitation energy of 11.9 MeV. Four collective structures have been identified based on two-quasineutron configurations. The low-lying states of both parities, as well as the main ΔI=2 regular structures observed at high spin, are described in the framework of the interacting boson-fermion model with broken pairs.

The g -factors of the ground state band members up to the 10 + level and of the 2 + state in the γ-vibrational band have been measured in 164,166,168 Er using the Coulomb excitation transient field technique. In the g-band the g -factor values were found to be nearly constant as a function of spin. For the 2 + states of the γ-band, values about 20% larger than those in the g-band have been determined. This latter fact is consistent with the known decay properties of the γ-band.

Excited states of neutron deficient nuclei close to Sn-100 were investigated in an in-beam spectroscopic experiment using the NORDBALL detector array. Excited states in Cd-99 were identified for the first time. The measured half-life of an isomeric state in Cd-99 indicates that the stability with respect to quadrupole shape changes is as large in Sn-100 as for other heavy doubly magic nuclei.

Six superdeformed (SD) bands have been observed in the nucleus {sup 148}Gd using the {gamma}-spectrometer GASP. The structure of the observed SD bands is discussed within the concept of cranked-Strutinsky-type calculations including pairing interaction. For the configuration assignments two different parametrizations of the Woods-Saxon potential are compared. Five of the observed SD bands are described in terms of quasiparticle configurations, whereas one is suggested to have vibrational-like structure. From this data a {Delta}{ital I}=2 staggering in the rotational spectrum of the yrast SD band also has been observed. {copyright} {ital 1996 The American Physical Society.}

The neutron deficient 141Tb nucleus has been studied with the 92Mo (54Fe, alphap) reaction at 240-MeV incident energy and the multidetector array GASP. For the yrast pih11/2 decoupled band, excited states up to 6.7 MeV and spin up to 47/2- have been observed. This band presents an upbend at rotational frequency of omega = 0.38 MeV due to the alignment of h11/2 protons. The results are discussed in terms of the Cranking model.

Experimental data collected so far demonstrate that the population of superdeformed (SD) structures in nuclei with mass A∼150 is influenced by the asymmetry in the entrance channel of the reaction. Furthermore, evidences for the population of hyperdeformed (HD) structures in the same mass region have been obtained only when charged particles are emitted in the evaporation chain. Dynamical model calculations show that in the reactions used to populate SD bands the equilibration times of the compound nuclei are not very sensitive on the mass asymmetry of the entrance channel. A qualitative understanding of both phenomena (SD and HD) is obtained assuming a link between the population of evaporation residues at very high spin and the dynamical hindrance of fission. Recent experimental results obtained in this field at the GASP spectrometer are presented for the case of the152Dy nucleus populated in the37Cl+120Sn reaction. Proton and alpha particle spectra in coincidence with SD structures have been obtained. A sizeable difference is evidenced between alpha particle spectra in coincidence with SD and normally deformed structures.