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Level lifetimes for the candidate chiral doublet bands of $^{80}$Br were extracted by means of the Doppler-shift attenuation method. The absolute transition probabilities derived from the lifetimes agree well with the M1 and E2 chiral electromagnetic selection rules, and are well reproduced by the triaxial particle rotor model calculations. Such good agreements among the experimental data, selection rules of chiral doublet bands and theoretical calculations are rare and outstanding in researches of nuclear chirality. Besides odd-odd Cs isotopes, odd-odd Br isotopes in the A≈ 80 mass region represent another territory that exhibits the ideal selection rules expected for chiral doublet bands.

The neutron-deficient nucleus 75Kr has been studied in two EUROBALL experiments. The analysis yielded a considerably extended level scheme including two newly observed excited high spin bands. The results are interpreted in the framework of the cranked Nilsson-Strutinsky approach. The calculations compare well to the experimentally established level scheme and predict the nucleus to be mainly prolate or triaxially deformed at high spin. Evidence for an oblate-prolate shape coexistence could not be found at high spin.

High-spin states in 73Kr were studied at the XTU tandem accelerator of the Laboratori Nazionali di Legnaro using the reaction 40Ca(40 Ca,2pn) at a beam energy of 185 MeV. Gamma rays were detected with the EUROBALL spectrometer. Particle detection enabled us to identify the reaction channel leading to 73Kr. The yrast bands of positive and negative parity were established up to probable spins of 61/2+ and 63/2- , respectively. The energies of the two identified bands agree well with the predictions of the configuration-dependent Cranked Nilsson-Strutinsky approximation and indicate that the nucleus remains collective up to the maximum spins of the respective high-spin configurations. The positive-parity band represents one of the rare cases where band non-termination at the highest spin of the configuration could be established experimentally.

High-spin states in 83Rb were populated in the reaction 11B + 76Ge at beam energies of 45 and 50 MeV. Gamma rays were detected with the spectrometer GASP. The level scheme of 83Rb was extended up to 13.9 MeV. Mean lifetimes of 23 levels were determined using the Doppler-shift-attenuation method. Among the bands newly established is a sequence including intense M1 transitions and cross-over E2 transitions. This sequence turns out to be irregular and thus shows that magnetic rotation observed in the neighboring odd-odd isotopes cannot be sustained in this odd-even nuclide. Excited states in 83Rb were interpreted in terms of the shell model using the model space pi (0f5/2, 1p3/2, 1p1/2, 0g9/2) nu (1p1/2, 0g9/2). The configuration predicted for the M1 sequence is analogous to the one predicted for the M1 band in the neighbor 84Rb and reproduces the transition strengths at high spin.

Dipole and quadrupole excitations in the semimagic N=50 Nucleus 88Sr were investigated at the superconducting Darmsatdt linear accelerator S-DALINAC with bremsstrahlung of an endpoint energy of 6.8 MeV. Many new dipole excitations could be identified, and their reduced transition probabilities were determined. The experimental findings are discussed in the context of quasiparticle-phonon-model and shell-model calculations. A breaking of the N=50 core is essential to describe the structure of the observed excitations. The two-phonon quadrupole-octupole Jpi=1- state exhibits unusual features which are presently not understood.

The nucleus 70Se was studied using the 40Ca(40Ca, 2α) reaction at a beam energy of 185 MeV. Gamma rays were measured with the EUROBALL III spectrometer. The known positive-parity bands have been extended and one new band of positive parity and two of negative parity have been identified. These bands are interpreted in terms of the cranked Nilsson-Strutinsky approach. Calculations suggest that the two negative-parity bands, which have the same signature, are both based on a configuration with two protons and three neutrons lifted from the fp shell to the g9/2 orbital, but at different nuclear shapes. This represents a shape coexistence at high spin.

High-spin states in 82Rb and 84Rb were populated in the reaction 11B + 76Ge at beam energies of 45 and 50 MeV. Gamma rays were detected with the spectrometer GASP. The level schemes of 82Rb and 84Rb were extended up to 6.0 and 7.4 MeV, respectively. Mean lifetimes of five levels in 82Rb and eleven levels in 84Rb were determined using the Doppler-shift-attenuation method. Regular magnetic dipole bands including strong M1 and weak E2 transitions observed in both nuclei show the characteristic features of magnetic rotation. These bands have been successfully described in the tilted-axis cranking model on the basis of the four-quasiparticle configuration pi(fp) pi(g_{9/2}^2) \nu(g_{9/2}). The calculations reproduce the band-like properties as well as absolute B(M1) and B(E2) transition strengths in both nuclei, which supports the concept of magnetic rotation. Excited states in 84Rb were also interpreted in terms of the shell model using the model space pi(0f_{5/2},1p_{3/2},1p_{1/2},0g_{9/2}) nu(1p_{1/2},0g_{9/2}). These calculations reproduce the low-spin states. Moreover, calculated states with the main configuration pi(0f_{5/2}^{-2}1p_{3/2}^{-1} 0g_{9/2}^2) nu(0g_{9/2}^{-3}) can be combined to M1 sequences that reproduce roughly the experimental transition strengths, but do not describe the features of magnetic rotation, as regular level spacings and B(M1) values decreasing with increasing rotational frequency.

Excited states of the nucleus 79Br were investigated via the reaction 76Ge(7Li,4n) at 35 MeV. Coincidence data of emitted gamma rays were measured with an arrangement of six EUROBALL CLUSTER detectors. The E2 bands built on the 9/2+ and 3/2- states were extended up to J = 37/2 at E \approx 8.8 MeV. The M1 band starting with a 15/2- state at 2.6 MeV was extended to J = (29/2) at E = 6.4 MeV. Cross-over E2 transitions within this band were observed for the first time. Mean lifetimes of 17 levels were deduced using the Doppler-shift-attenuation method. The M1 band can be described within theTilted-Axis-Cranking model on the basis of the tilted three-quasiparticle configuration pi(g9/2) nu (g9/2) nu (fp) which has a triaxial shape. This band appears as a mixed case including contributions of both, magnetic and collective rotation.

Excited states have been populated in In-108 and In-110 in complementary backed- and thin-target experiments, using the Stony Brook and the 8 pi Ge-detector arrays. The level schemes for both isotopes have been extended and modified, including the first observation of DeltaI = 2 bands in In-110. Lifetimes of states in four DeltaI = 1 bands and one DeltaI = 2 band have been measured using the Doppler-shift attenuation method. Experimental total angular momenta and reduced transition strengths for the DeltaI = 1 bands have been compared with tilted axis cranking predictions for shears bands with configurations involving one proton g(9/2) hole and one or three valence quasineutrons from the h(11/2) and g(7/2)/d(5/2) orbitals. The DeltaI = 2 bands have been compared with principal axis cranking predictions for configurations with two g(9/2) proton holes and a g(7/2) or d(5/2) proton and one- or three-quasineutron configurations involving the h(11/2) and g(7/2)/d(5/2) orbitals. In general, there is good overall agreement for both the angular momenta and reduced transition strengths. The DeltaI = 1 and DeltaI = 2 bands have large J((2))/B (E2) ratios as expected for the shears mechanism. The B (M1) strengths deduced for the DeltaI = 1 bands show a decreasing trend as a function of spin, which is also a feature of the shears mechanism. Configuration assignments have been made for most observed bands based on comparisons with theory and systematics of neighboring nuclei.

Dipole excitations in the spherical nucleus 88Sr, observed in the energy region 4.5 MeV < E_x < 5.5 MeV, are proposed to be scissors-like excitations on top of the dynamically deformed quadrupole vibrational state.

A 4 PI silicon ball for detection and identification of light charged particles in large multidetector -arrays as EUROBALL is presented. The design is based on a N=42 ball with 12 pentagons and 30 hexagons as used in the GASP array. The absorptive material for -rays is minimized to the detector thickness of 300 or 500µm and a 0.63 mm ceramic backing. The geometrical coverage is designed for about 90% of 4. A pulse shape discrimination method with totally depleted detectors working in the reverse mount allows identifying protons and -particles above an energy threshold of about 2MeV. The performances of the ball were tested at the tandem - booster accelerator combination of the MPI Heidelberg in two experiments using the high-recoil reaction of 228MeV 58Ni+46Ti and the low-recoil reaction of 95MeV 16O+58Ni. The two-dimensional spectra of zero-crossing (ZC) versus energy confirmed an excellent discrimination of protons and -particles in all the detectors at different angles. The energy spectra of protons and -particles measured in the experiments are presented, too. The -spectra measured in coincidence with various combinations of emitted particles showed a high selectivity of the ball. The reduced total efficiency for protons of 59% and 55% and -particles of 44% and 32% measured in a nuclear spectroscopy application is analyzed in a Monte-Carlo simulation (GEANT). It is due to a combined influence of a thick target needed to stop the recoiling residual nuclei and thick absorbers needed to protect the Si-detectors from scattered beam. The results along with the GEANT extrapolation to optimum experimental conditions confirm that RoSiB is a highly efficient and selective device for identification of rare reaction channels with heavy ions.

High-spin states in 72Br were studied with the EUROBALL III spectrometer . The negative-parity band observed in this experiment displays a signature inversion around spin I = 16. The interpretation within cranked Nilsson-Strutinsky approach shows that this signature pattern is a signal of a substantial triaxial shape change with increasing spin where the nucleus evolves from a triaxial shape with rotation around the intermediate axis at low spin through an axially symmetric prolate one to a triaxial shape but with rotation around the shortest principal axis at high spin. This is the first case in which signature inversion was clearly related to varying gamma deformation.

In nuclei in the mass region of $A \approx 70 - 90$ a variety of phenomena is observed which are based on single-particle and collective motion of the nucleons. We discuss the properties of Br and Rb isotopes with neutron numbers of 38 - 48. In light Br isotopes ($N$ = 37, 38) rotational bands have been observed up to spins of 65/2 and rotational frequencies of 1.8 MeV. Both features can be described in terms of the cranked Nilsson-Strutinsky formalism. In Rb nuclei with $N$ = 45, 47 we found regular magnetic dipole bands evolving at high spin whereas the low-spin structure of those less deformed nuclei is irregular. These magnetic dipole bands represent magnetic rotation, a new rotational mode predicted by the tilted-axis cranking model. In nuclei at $N$ = 48 we found small collectivity in low-spin states and multiplets based on multi-particle excitations at high spin. These properties are interpreted in terms of the shell-model.

High-spin states in 72Br and 73Br were studied with the EUROBALL III spectrometer. The negative-parity band observed in 72Br displays a signature inversion around spin I = 16. Fully consistent cranked Nilsson-Strutinsky calculations show that this signature inversion can only be understood if the nuclear shape evolves from a triaxial shape with rotation around the intermediate axis at low spin through a collective prolate shape to a triaxial shape with rotation around the shortest principal axis at high spin. Rotational bands in 73Br were observed up to spins of I = 65/2 at excitation energies of 26 MeV. Cranked Nilsson-Strutinsky calculations indicate that one of the negative-parity bands terminates at spin 63/2. Since this spin coincides with the maximum spin observed in the corresponding experimental band, we conclude that we observed this band up to its termination.

We report on a nuclear resonance fluorescence experiment on the semi-magic odd-mass fp-shell nucleus 51V. The detected dipole strength distribution is discussed on the basis of modern shell-model calculations employing a model space allowing for excitations of protons and neutrons from the 1f7/2 to the (2p1/2,2p3/2,1f5/2) shells. The calculations indicate that the main body of transitions is of magnetic dipole type, and they are capable of reproducing the observed distribution well. Possible electric dipole and quadrupole contributions are also discussed.

Results of a 208 Pb (gamma,gamma') experiment are presented aiming at an identification of the 2 + member of the long-sought two-octupole phonon multiplet. Four E2 excitations have been observed below 6.5 MeV excitation energy, two of them for the first time. However, in contrast to new results of calculations within the quasiparticle-phonon nuclear model (QPM), no obvious candidate for the two-octupole phonon vibration could be found in the present study. We discuss the J pi=2+ states detected in this as well as previous experiments with respect to their possible two-octupole phonon structure.

High-spin states of the nucleus $^{88}$Sr have been studied via the reaction $^{80}$Se($^{11}$B,$p$2$n$) at a beam energy of 45 MeV. Gamma-rays were detected with the six-detector array OSIRIS CUBE. The level scheme of $^{88}$Sr has been extended up to $E \approx$ 11 MeV and $J = 17$. Mean lifetimes of three levels have been determined using the Doppler-shift-attenuation method. The level structures in $^{88}$Sr have been interpreted in terms of the shell model. The calculations were performed in the configuration space $(0f_{5/2}, 1p_{3/2}, 1p_{1/2}, 0g_{9/2})$ for the protons and $(1p_{1/2}, 0g_{9/2}, 1d_{5/2})$ for the neutrons. These calculations describe the high-spin level sequences linked by $M1$ transitions with strengths of $B(M1) \leq 1.4$ W.u. as multiplets of seniority $\upsilon$ = 4 and 6 states including proton configurations and neutron-core excitations.

High spin states have been populated in 117 53I via the 90Zr(31P,2p2n) reaction at 150 MeV, using the EUROGAM II γ-ray spectrometer to record high-fold γ-ray coincidences. A quadruples γ-ray analysis (γ4) has been used to extend the known level scheme. In addition to several aligned noncollective states, a new high-spin band showing characteristics of smooth termination has been established at and linked into the low-spin level scheme. Its structure has been inferred through comparison with cranked Nilsson-Strutinsky calculations.

Excited states in the N=Z nucleus 70Br have been investigated using the reaction 58Ni(16O,1p3n). Gamma rays were detected with one EUROBALL CLUSTER detector and three single HPGe detectors. Charged particles and neutrons were registered with the Rossendorf silicon ball and six modules of the EUROBALL neutron wall, respectively. The identification of gamma transitions in 70Br is based on the analysis of gamma-gamma-proton-neutron coincidences. A level scheme of 70Br has been established for the first time. It shows a multiplet-like structure of probably isospin T = 0 while T = 1 isobaric analogue states are not observed.