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At the projectile-fragment separator FRS of GSI, relativistic secondary beams of about 520 MeV/nucleon were produced by fragmentation of a primary beam of58Ni at 650 MeV/nucleon in a beryllium target. By means of a?E—B?—TOF measurement, the fragments have been identified and their charge-changing probabilities in targets of CH2, C, Al, and Pb have been determined. We describe the results for the total charge-changing cross sections in this first paper, whereas a second article deals with the partial charge-changing cross sections. At the drip line, the measured charge-changing cross sections exhaust close to 100% of the total interaction cross sections as calculated with semiempirical models. The measurements at the proton drip line with low-Z targets indicate that only a very small increase of the cross sections may be observed, whereas the measurements with a lead target show that no significant increase of the total charge-changing cross sections is present which would be a hint for low-lying dipole strength. Our experimental data are compared to Glauber-type calculations.

Total interaction cross sections have been measured for8Li on C and Pb targets, for9Li on C, Al, Cu, Sn and Pb targets as well as for11Li on C, Sn and Pb targets. For each beam, we also used a plastic scintillator as target. The measurements with the scintillator targets are used to extract reduced nuclear radii of the lithium isotopes. These radii are then used for the calculation of the nuclear part of the total cross section for the other targets. The total electromagnetic-dissociation (EMD) cross sections have been deduced and are compared to different models. A strong target-charge-dependent EMD cross section is measured for11Li reaching 2.96-0.82+0.84 b for the Pb target. In the9Li case, a large EMD cross section for high-Z targets has been observed which amounts to 0.75 ± 0.45 b for the Pb target. The EMD cross sections of both,9Li and11Li, may be understood by the giantdipole-resonance model.

For the compound nucleus179Au formed at an excitation energy of 26 MeV in the fusion reaction90Zr+89Y, the energy spectra of promptly emitted protons,a particles and? rays were measured in concidence with the evaporation residues. On the basis of the measured total decay energy, the 1p and 1a decay channels were separated from all other evaporation-residue channels. The energy spectra and absolute cross sections, together with previously measured excitation functions for various decay channels, are successfully described by statisticalmodel calculations with the Monte Carlo code CODEX.

A microscopic calculation of nuclear state densities was performed starting from realistic single-particle levels. Within this concept, a correspondence between microscopic ground state energy corrections and microscopic effects on state densities was deduced. It is shown that the approximations introduced by a simple analytical expression for the nuclear state density are comparable to the uncertainties of microscopically calculated state densities for nuclei in their ground state configuration. Guidelines for the determination of the parameters of this analytical expression were deduced from the microscopic computations.

Total charge-changing cross sections have been measured for8Li on C and Pb targets, for9Li on C, Al, Cu, Sn and Pb targets, as well as for11Li on C, Sn and Pb targets at about 80 MeV/nucleon. These data are compared to measured total reaction cross sections and Glauber-type calculations using Hartree-Fock density distributions. These comparisons allow to draw conclusions on the proton density distribution of the neutronrich lithium isotopes. The results show that even for the most exotic nucleus11Li the proton distribution is only very weakly influenced by the long tail in the neutron density distribution already established in several experiments.

We have measured production cross-sections of the new neutron-rich isotopes58Ti,61V,63Cr,66Mn,69Fe,71Co and neighbouring isotopes that have been identified as projectile fragments from reactions between a 500 MeV/u86Kr beam and a beryllium target. The isotope identification was performed with the zero-degree magnetic spectrometer FRS at GSI, using in addition time-of-flight and energy-loss measurements. The experimental production cross-sections for the new nuclides and neighbouring isotopes are compared with an empirical parametrization. The resulting prospects for reaching even more neutron-rich isotopes, such as the doubly-magic nuclide78Ni, are discussed.

The beta-gamma spectroscopic study of22O is presented. This nucleus, produced as a projectile-like fragment from the interaction of a 60 MeV/n40Ar beam with a Be target, has been separated by the LISE spectrometer. Several gamma rays from22O decay have been observed, from which a half-life of (2.25±0.15)s has been determined. Accurate excitation energies have been deduced for several states in22F. A partial beta decay scheme of22O has been established. Experimental results have been compared with shell model calculations.

The new isotope184Pb has been produced through40Ca +147,148Sm reactions, and detected by its a radioactivity (Ea = 6618 ± 10 keV). The detection technique involves thermalization of recoil nuclei in a gas and electrostatic collection onto the active surface of a solid state detector. The identification is made on the basis of the (40Ca,xn) excitation functions, and of the time correlation with the a-decay of the daughter180Hg.

The thirteen above-listed isotopes have been produced at GANIL by fragmentation of a40Ar beam at 60 MeV/nucleon. The LISE spectrometer allowed us to isotopiaally separate these nuclei. Beta delayed gamma spectroscopy was carried out for the first time for eleven isotopes and additional information was obtained for another two.

The new beta-delayed neutron emitter15B has been observed. The measured half-life is 11 ms ±1 ms and limits have been set on other decay channels: P0n<5%, P2n<1.5%. The beta emitter12Be has been separated, unambiguously identified, and its half-life has been measured to be 24±1 ms.