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One of the most exciting subjects in contemporary nuclear physics is the study of nuclei at the limits of stability with respect to particle emission. Recently, there has been an intensive experimental activity in measuring proton decay and a large variety of proton emitters were observed in the region of nuclei with 50 < Z < 82. Very recently, the proton radioactivity from 117La and 121Pr has been identified and the decay rate deviates significantly from calculations assuming spherical configurations, thus indicating the onset of large deformations in the drip line nuclei below Z = 69. Predictions by the microscopicmacroscopicmass model and by relativistic mean field calculations support these experimental results and suggest the position of the proton drip line. The lifetimes of the proton-decaying isomers are extremely sensitive to the orbital angular momentum ` of the emitted proton and can vary over several orders of magnitude when changing the angular momentum of the occupied orbital. The position of certain orbitals at the Fermi surface depends strongly on the beta2 deformation. It is therefore very important to determine the quadrupole deformation of the nuclei at and beyond the proton drip line, in order to locate the orbitals close to the Fermi surface and to estimate the lifetime of the isomers, which is essential when looking for new proton emitters. The deformation of the nuclei at the proton drip line in the A 130 mass region can be experimentally tested by comparing the lifetimes of proton emitters with theoretical predictions and by investigating the level structure of particle bound nuclei close to the drip line. For Z = 57 the proton drip line is predicted to correspond to the isotope 118La. The lightest La nucleus for which spectroscopic information has been published is 124La . This thesis bescribes an experiment realised to identify for the first time excited states of the doubly-odd nucleus 122 57 La65. Another aspect that make particularly interesting a study of these nuclei is a well-established phenomenon in two-quasiparticle rotational bands in odd-odd nuclei: the signature inversion. Despite the observation of signature inversion in many different nuclei, and numerous theoretical interpretations, a satisfactory explanation of the phenomenon has yet to be found. We want verify if the experimental level scheme of 122La is in agreement with the systematics of the other nuclei in this mass region. The common feature relating the studies of these neutron deficient nuclei is that they are populated with extremely low cross section and require special techniques to be identified. The standard efficient way to achieve this is the use of arrays of high-purity germanium detectors coupled to specific ancillary devices for their selection. Our experiment has been performed at the Legnaro National Laboratory (LNL) where heavy-ion fusion-evaporation reaction 40Ca(@ 200 MeV)+92Mo was performed to establish the scheme of 122La by using the GASP -ray spectrometer in conjunction with the ancillary charged-particle ISIS detector and the Neutron Ring. This experimental set-up led to numerous achievements in the A 130 mass region. Chapter 1 introduces to the physics of the nuclei close and beyond to the proton drip-line. In Chapter 2 we will briey see the various theoretical models created to describe several types of nuclear excitations and discuss in more detail the cranking model. Chapter 3 describes the experimental techniques of -ray spectroscopy and the setup used for the present measurement. In Chapter 4 the steps followed in the sorting of the raw data to produce particle-gated matrices are described, together with the techniques used to select the different reaction channels and to clean the spectra. Chapter 5 shows the systematic features of the rotational bands of the A 130 proton rich odd-odd nuclei. Chapter 6 will be devoted to the construction of the decay scheme and to the spins assignments, performed through the analysis of gated matrices, transition intensities, DCO, and the comparison with the systematics of the La isotopes. Finally, in Chapter 7, the results are discussed in the light of the deduced experimental quantities like single-particle spin alignment, dynamic moments of inertia, signature splitting, and B(M1)=B(E2) branching ratios to assign the Nilsson orbitals to the found bands.

The even-even nucleus 126Ce was studied via in-beam -ray spectroscopy using the 40Ca + 92Mo reaction at 190 MeV. Five bands were observed, one of them being identified for the first time. New connecting transitions were identified between the bands, which lead to new spin assignments. The bands are discussed in the framework of the IBM + broken pairs model.

The odd-even nucleus Ce-125 was studied via in-beam gamma-ray spectroscopy using the Ca-40 + Mo-92 reaction at 190 MeV. Four rotational bands were observed, two of them being identified for the first time.New connecting transitionswere identified between the bands, which leads tp new spin assignments for one of the previopusly known bands.We propose J=7/2(-) for the ground state of Ce-125.The bands are discussed

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.

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 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 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.

High spin states up toJ=14 and excitation energy up toE *=3076 keV have been observed in the odd-odd nucleus100Tc with the reaction96Zr(7Li, 3n), at bombarding energies between 21 and 31 MeV, by in-beam γ spectroscopy and conversion-electron measurements. A ΔJ=1 negative parity band similar to that observed in theN=57 isotone102Rh, and based on the 8−, 708 keV state has been identified. The observed band can be interpreted in terms of collective core excitations based on a two-quasiparticle state of(πg9/2 ⊗ νh11/2) configuration. Comparison with IBFM-2 calculations have been performed.

The evolution of the octupole excitation is investigated along the Th isotope chain. The isotope 226Th results to be close to the critical point (square-well potential in the octupole amplitude $\beta_3$ ).

We present a detailed analysis of nuclear structure properties concerning99,101Ru and101,103Rh, within the framework of the Interacting Boson-Fermion Model (IBFM) version 2, where both neutron and proton degrees of freedom are taken into account. Calculated energy spectra, electromagnetic moments, transition probabilities and spectroscopic factors for one-nucleon transfer reactions are compared with the corresponding experimental data.

Conversion electrons,γ and X rays from102Rhm (6+,T 1/2=1057 d) have been studied. An electromagnetic branch (2.3±0.3) ·10−3 feeding the102Rh first excited state has been observed in the 6+ isomeric decay. The excitation energy of the 6+ isomer turns out to be 140.7 keV above the 2− ground state.

Theg-factor of the 7+ state in100Rh withT1/2=140(5) ns and of the 6− state in104Rh withT1/2=47(3)ns has been measured by the time-differential perturbedγ-ray angular distribution method (TDPAD). The obtained values are +0.67(2) and +0.33(1) respectively. The two nuclei were populated with reactions induced by7Li on96,100Mo at a bombarding energy of 30 MeV. Shell model calculations using effective single particle moments show that the 7+ state in100Rh has mostly a πg9/2 ⊗ vd5/2 configuration, while the main component of the 6− state in104Rh is the πg9/2 ⊗ vh11/2.

The mean life of the 12+ level at 4195 keV in146Sm has been measured with the Recoil Distance method. The reduced strength of the E3 decay 12+→9−, about 60 W.u., confirms the collectivedouble-octupole character of the 12+ level.

The structure of 105Sn has been investigated through the 50Cr(58Ni,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 experimental results are in agreement with the prediction of Tilted Axis Cranking calculations, which satisfactorily explain the properties of the band.

Theg-factor of the 8+ isomer of142Eu with mean lifeτ=9 ns, has been measured by the time-differential perturbedγ ray angular distribution (TDPAD) method. The 8+ isomer was populated with the reaction114Cd(32S,p3n)142Eu at 155 MeV. The obtained valueg(8+)=0.51(3) agrees with shell model calculations using effective single-particle moments taken from neighbouring nuclei. A main configurationπh11/2⊗(vh11/2)−1 has been confirmed for the 8+ isomer.

High spin states of 146 Dy above the 10+ isomer have been identified by means ofγ- recoil andγ }-γ coincidences through the reaction90 Zr(58 Ni, 2pat a bombarding energy of 250 Me V. The level scheme is discussed in terms of the coupling of 2h11/2 protons to the N=80 core vibrations.

Two new isomers with half- lives of 0.67(6) μs and 2.8(3) μs have been identified in the odd-odd nucleus144Tb. A partial decay scheme is presented. An interpretation in the framework of the shell model is discussed for the low lying energy states.

High-spin states up to I=22ħ have been observed for the first time in the odd-odd nucleus142Eu above the 8− β+ -decaying isomer. A new isomer of mean life τm=9.0± 0.6 ns and Jπ=8+ has been identified. The low energy part of the level scheme is interpreted in terms of single-particle excitations in the 2d5/2 and h11/2 orbitals and of the N=80 core excitations.

Low-lying levels of100Rh have been investigated with the reaction100Ru(p, nγ)100Rh in the proton energy range 4.4 MeV≦Ep≦6 MeV.

An isomeric level has been found in102Rh, lying 41.9 keV above the τm = 297 d,Jπ = 2- state. The lifetime of the new isomer comes out to be τm = = (27.3±0.6) ns. TheK-conversion coefficient of the 41.9 keV transition by which it decays has been measured to be αK = 4.40±0.45.

The mean life of the lowest 21/2(+ level of89Zr has been measured with a pulsed7Li beam and the85Rb(7Li, 3n)89Zr reaction.

The previously known level scheme of45Sc has been extended with the addition of four more high-spin states. The decay of the new level at 3294 keV identifies it as the 15+/2 member of theK = 3/2 « quasi-rotational band ». The new levels at 3570, 3693 and 5419 keV decay through the negative-parity cascade 15-/2 → 11-/2 → 7-/2. A negative parity has been attributed to them, and the spin values 17/2, 19/2 (21/2 or 23/2) have been deduced from angular correlations. This set of high-spin states has been discussed in connection with the spherical shell model and the rotational model.

The level scheme of102Rh has been investigated by the102Ru(p, nγ) reaction in the proton energy range 3.1 MeV≦Ep≦6 MeV. Excitation functions,γ-γ coincidences and pulsed beam measurements have been performed and a level scheme including 33 excited states up toEx≈650 keV has been constructed. Theγ-branchings of several levels have also been measured. The lifetimes of 5 excited states have been determined with the centroid-shift method:τm(105.2 keV)=(1.3±0.3) ns,τm(123.7 keV)=(0.6±0.3) ns,τm(178.6 keV)=(1.5±0.3) ns,τm(208.7 keV)=(0.5±0.3) ns,τm(359.6 keV)=(0.8±0.4) ns. Upper limits have been placed for the lifetimes of 20 other levels.

The level structure of96Tc has been investigated by means of the93Nb(α, n)96Tc reaction. Excitation functions have been measured for some γ-transitions in the energy intervalEα=(11÷14) MeV. Gammagamma coincidence measurements have been made with two germanium detectors atEα=10.8 and 14.0 MeV. A new low-lying level at 49.1 keV withJ=6 and a mean life

A new version of the “recoil distance method”, making use of a gas target, has been used to determine the lifetime of the 871 keV level in17O and of the 495 keV level in17F. The measured values of the lifetimes are (2.32±0.08) · 10−10 sec and (3.96±0.10) · 10−10 sec for17O and17F, respectively.

The mean life of the33Cl 1985 keV (5/2+) second excited level τ=(94−20+14) fs and a lower limit τ≥250 fs for the 810 keV (1/2+) first excited level have been measured with the Doppler-shift attenuation method by means of the reaction32S(p, γ)33Cl. The strengths of the 5/2+→3/2+ g.s. transitions have been compared in mirror nuclei33Cl and33S. The relative importance of the isoscalar and of the two isovector terms in theM1 transition amplitudes has been obtained from β andM1 strengths in «analogous» transitions.

The mean lives of a number of excited states of30P have been measured with a D.S.A. technique. The reaction29Si(p, γ)30P has been used at the resonancesEp =731, 1506, 1686, 1748 and 1772 keV. The decay of each resonance has been checked. For some levels, discrepancies have been found with other results. The method for analysis and evaluation with an improved, simple fit of the energy loss formula is described in detail.