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The perspectives for photonuclear experiments at the new Extreme Light Infrastructure - Nuclear Physics (ELI-NP) facility are discussed in view of the need to accumulate novel and more precise nuclear data. The parameters of the ELI-NP gamma beam system are presented. The emerging experimental program, which will be realized at ELI-NP, is presented. Examples of day-one experiments with the nuclear resonance fluorescence technique, photonuclear reaction measurements, photofission experiments and studies of nuclear collective excitation modes and competition between various decay channels are discussed. The advantages which ELI-NP provides for all these experiments compared to the existing facilities are discussed.

Low-energy isomeric states of 86Y were populated in the reaction 73Ge + 16O at 57MeV and were investigated by means of delayed n $ \gamma$ and $ \gamma$ $ \gamma$ coincidences. A half-life of 70(7)ns was measured for the 5- state at 208keV, yielding an exceptionally small B(M1) value of 2.0(7)×10-5 W.u. and a B(E2) value of 0.34(+24 -13) W.u. For the other three known isomeric states at 218, 243, and 302keV, the half-lives extracted from the present experimental data are in very good agreement with previous measurements. Given the newly observed isomeric character of the 5- 208keV state, the re-analysis of earlier experimental data on the 302keV isomer led to a new spin-parity assignment, 6+, for this state. In addition, this re-evaluation provided two g -factors, -0.083(3) and +0.63(2) , for the 208 and 302keV states, respectively. The results are discussed in terms of spherical-shell model calculations performed with a truncated space of configurations built on the f 5/2 , p 3/2 , p 1/2 , and g 9/2 valence orbitals. Effective spin, orbital, and “tensor” g -factors were determined empirically for protons and neutrons in the considered configuration space.

The evolution of the structure of the gamma-vibrational band head 2+ γ in well-deformed rare-earth nuclei is studied within the framework of RPA calculations using a quasiboson approximation based on the Nilsson model. The obtained evolution of the quasiparticle structure of the gamma-vibrational band head is shown to correlate well with the evolution of the same nuclei within the IBA symmetry triangle when described in the extended consistent-Q formalism. An empirical relation is presented that links the IBA parameter χ with the quasiparticle structure of the gamma-vibrational band head.

Neutron-rich radioactive ion beams available from the HRIBF allow a variety of measurements around the 132Sn region, including Coulomb excitation and single-nucleon transfer. The B(E2;0+ → 2+) values for first 2+ excited states of even-even neutron-rich 132-136Te and 126-130Sn have been measured by Coulomb excitation in inverse kinematics. Neutron transfer onto a 134Te beam from 9Be and 13C targets, to populate single-particle states in 135Te, has also been studied. Gamma rays from the 13C(134Te, 12C) reaction were used to identify the νi13/2 state in 135Te, at an energy of 2109 keV. These and other results, and plans for future experiments with these neutron-rich beams, are presented.

Dynamical symmetries played a major role in interpreting collective nuclear spectra. Recent studies show that the nuclear system presents a phase transitional behavior in its evolution from spherical to deformed shape and new symmetries describe the structure at the critical point.

The low-spin excitations of the nucleus 146Sm which is just two neutrons and two protons away from the N = 82 shell and Z = 64 subshell closures have been investigated by means of the 143Nd (α, n) and 144Nd (α, 2n) fusion-evaporation reactions. We established 47 hitherto unknown energy levels up to 4.7MeV and 75 new transitions. In addition, 7 spin assignments were possible from the γ-γ angular correlation analysis. The structure of the possible candidates for a 2+ ⊗ 3− quadrupole-octupole multiplet are first discussed in terms of the harmonic vibrational model. A comparison of these states with the corresponding ones in the neighboring N = 84 isotones is also presented. Finally, the structure of the 146Sm nucleus is interpreted in terms of the IBA-spdf model. It is shown that the model is able to reproduce the experimental relative transition strengths of the 2+ ⊗ 3− quadrupole-octupole multiplet and also a series of collective properties such as the proposed double-octupole excitations.

The Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory has recently produced the world's first post-accelerated beams of heavy neutron-rich nuclei. The first experiments with these beam are described, and the results discussed. B(E2;0+ → 2+) values for neutron-rich 126,128Sn and 132,134,136Te isotopes have been measured by Coulomb excitation in inverse kinematics. The results for 132Te and 134Te (N = 80, 82) show excellent agreement with systematics of lighter Te isotopes, but the B(E2) value for 136Te (N = 84) is unexpectedly small. Single-neutron transfer reactions with a 134Te beam on natBe and 13C targets at energies just above the Coulomb barrier have also been studied.

The lifetimes of low-lying negative parity yrast levels have been measured in131La using the recoil distance Doppler shift method. The nuclear reaction employed was116Cd+19F at a beam energy of 80 MeV. The data were analysed using the differential decay curve method. The E2 transition strengths for negative parity yrast states and the energy spectra are well described by coupling a fermion to aγ-soft core in the frame of the interacting boson fermion approximation model.

The effects of the neutron-proton interaction on the low-lying levels of Mo and Cd isotopes have been considered in the frame of the IBA-1 model by taking into account an effective boson number (Neff). Both an empirical procedure based on previous IBA-2 mixing calculations and the Np AT, scheme provide comparable Neff values. Level spectra and electromagnetic transitions are investigated. The results support the idea that IBA-1 calculations with a suitable Neff can largely simulate IBA-2 mixing calculations, taking advantage of simplicity and a smaller number of parameters. PACS: 21.60.Ev

132Te has been studied through β- decay of 132Sb radioactive beam at HRIBF leading to a significantly revised level scheme. A number of newly identified, likely 2+ states allows for a test of recent quasiparticle random phase approximation calculations with a density-dependent pairing force. In addition, the removal of a previously proposed 3− state allows for a simple shell model interpretation of the low-lying negative-parity states.

A consistent-Q formalism extended to an IBA-1 Hamiltonian applicable also in theU(5) limit, is applied to Ru and Pd isotopes withN around 60. A good description of energy levels andE2 transitions in these nuclei is obtained. The model is able to reproduce the main features of this transitional region, characterized by both rigid triaxial deformation andγ-softness.

Two new absolute transition rates are reported for the nucleus144Sm following an (α, α′) Coulomb excitation study. They are B(E3; 3−→ 0+)=(38±3) W.u. and B(E1;3− → 2+)=(2.8±0.4)×10−3 W.u. This large E1 matrix element, along with the previously known B(E1; 1− →+) value support the interpretation of the 1− state in this nucleus as 2-phonon 2+ × 3− excitation. In the frame of the IBM-1 +f-boson model we show the need for a two-body term in the E1 transition operator. Estimates for the strengths of the one and two-body parts of the E1 transition operator are obtained from these experimental data.