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What constitutes an element? The ancient Greeks believed in four elements: earth, wind, fire and water. By the l920s, however, physicists were defining elements according to the number of protons within the atomic nucleus. Meanwhile, pioneering work by Frederick Soddy and Kasimir Fajans demonstrated the existence of different isotopes – atoms that have similar chemical properties but different masses. This work culminated in 1932 with James Chadwick's discovery of the neutron, the uncharged particle that effectively damps out the Coulomb repulsion between the charged protons.

In experiments at GANIL and GSI, we explored the proton drip line to search for new isotopes and to study the decay modes of nuclei close to the drip line. The study of -delayed proton emission of revealed a very nice agreement between theory and experiment. Studies at GSI enabled us to observe the new isotopes , , and , the latter one being the neighbouring isotope of the doubly-magic nucleus . Finally, at GANIL, the fragmentation of showed clear evidence for the new isotopes , , and . In addition, we performed half-life measurements on and nuclei in this mass region.

An in-medium effective NN interaction has been determined using the relativistic Hartree approximation in which coupling constants have been made density-dependent. For this calculation a saturation curve of nuclear matter has been built in such a manner that the saturation point can be reproduced and the compressibility is able to change, ranging from the Walecka model value to the Dirac - Brueckner one. Using this density-dependent NN interaction, we have studied the influence of the compressibility of nuclear matter on some physical observables like the Schrodinger-equivalent nucleon - nucleus optical potential or the Coulomb sum.

Principles of a new EAS detector are discussed. It is based on the so-called TTC (time-track complementarity) method, which implies the simultaneous measurement of incidence angles and arrival times of EAS muons. By means of only these measurements and using a single muon detector, the `muon eye', it is possible in principle to locate the EAS axis. The method of such a location, necessary formulae and accuracy estimates are presented. The latter have been obtained by simulations. The duty cycle and the acceptance of just a single detector have been shown to be rather large. The possible advantage of using more `muon eyes' is discussed.

Doubly differential cross sections for the double excitation of helium by high velocity protons are measured and compared with the predictions of the first-order Born approximation. Preliminary experimental data for the shapes and intensities of the resonances 2s2 1S, 2p2 1D and 2s2p 1P have been obtained from high resolution electron spectra at 20', 90' and 150' for a proton energy of 3 MeV. Both experiment and theory show that the excitation of the 1P resonance largely exceeds the 1D and 1S ones at this collision velocity. The shape and emission yield of the 1P line is well described by theory over the whole angular range. The agreement for the other two resonances is not always satisfactory.

The time evolution of single proton quasi-stationary states emitted from axially deformed nuclei is studied by solving numerically the two-dimensional time dependent Schrodinger equation. Angular distributions of emission with respect to the nuclear axis of symmetry are obtained. It is shown that the main escape paths are determined by the quantum numbers of the metastable state, rather than by the deformation of the potential. Combinations of such numerical studies of multidimensional quantum tunneling and angular distribution measurements from oriented deformed nuclei could provide invaluable nuclear structure information and imaging of Nilsson orbitals.

The characteristics of EAS with very small energies 104-105 GeV are calculated for the observation level 550 g cm-2. A three-dimensional Monte Carlo procedure is used, based on the well tested phenomenological model SM1 including nuclei fragmentation. It is shown that the calculated shower characteristics make it possible to realize a specific EAS experiment for the calibration of direct and indirect (EAS) methods used for mass composition investigation of primary cosmic radiation. A special selection of EAS is proposed which guarantees unbiased estimation of the relative contributions of the main primary nuclei groups at energies 104-105 GeV.

The presence of a M1 radiation in quasi-continuum spectra following (HI, xn) reactions is analysed within the wobbling model of Bohr and Mottelson. It is found that a M1 component is always present centered at about half the energy of the well known E2 bump. The M1 strength appears to be sensitive to the deformation parameters as well as the g-factors. Reasonable agreement with recent experimental data is found.