[en] New target systems for the ISOLDE on-line mass separator facility are presented. Targets of carbides, metal/graphite mixtures, foils of refractory metals, molten metals and oxides have been tested. Beams of high intensity of neutron-rich isotopes of a large number of elements are obtained from a uranium carbide target with a hot plasma-discharge ion source. A target of ZrO₂ has been shown to provide high intensity beams of neutron-deficient isotopes of Mn, Cu, Zn, Ga, Ge, As, Se, Br, Kr and Rb, while and SiC target with a hot plasma ion source gives intense beams of radioactive isotopes of a number of light elements. All these systems are rather chemically unselective. Chemically selective performance has been obtained for several systems, i.e.: the production of neutron-deficient Au from (³He, pxn) reactions on a Pt/graphite target with a hot plasma ion source; the production of neutron-deficient Lu and LuF⁺ and Hf and Hff⁺₃ from a Ta-foil target with a hot plasma ion source under CF₄ addition; the production of neutron-deficient Sr as SrF⁺ and Y as YF₂⁺ form a Nb-foil target with a W surface ionzer under CF₄ addition; the production of neutron- deficient Se as COSe⁺ from a ZrO₂ target with a hot plasma ion source under O₂ addition; and the production of radioactive F from an SiC target with a hot plasma ion source operating in Al vapour. (orig.)

[en] The recent developments of target systems for production of high intensity radioactive ion-beams at the ISOLDE mass separators is described. Methods for chemically selective production through separation of molecular ions are outlined and the effects of the addition of reactive gases has been studied. Results and further possible applications in the light element region are discussed. (author) 10 refs.; 9 figs.; 1 tab

[en] The β⁺/EC decay of the neutron deficient nuclei ⁷⁶,⁷⁸Sr and ⁷⁹Y was studied employing mass separated molecular beams of SrF⁺ and YF₂⁺ from the ISOLDE mass separator. The halflives of ^76,78Sr and ⁷⁹Y were measured as t_1/2=8.9(3)s, 159(8)s and 14.4(15)s, respectively, and decay schemes were established for ⁷⁶Sr and ⁷⁹Y. In the ⁷⁸Sr decay 10 new γ-ray transitions were identified. (orig.)

[en] Short communication

[en] Targets consisting of fine-grained powders of graphite and metals which do not form thermostable carbides have been investigated. The targets were heated to temperatures well above the melting point of the respective metals. A target of Pt powder mixed with graphite powder is found to be suitable for production of neutron deficient Au isotopes, when irradiated with 910 MeV ³He projectiles. The yields of neutron deficient Cd isotopes from a target of Sn powder mixed with graphite powder are also reported. (orig.)

[en] The conditions for production of radioactive ion-beams from targets of refractory metals by addition of CF₄ gas have been investigated. The production yields of chemically pure mass separated beams, obtained through the formation of molecular ions, are described for the elements Ca, Sc, Sr, Y, (Zr), Ba, Lu, and Hf. Improved release properties are obtained for several elements, owing to the formation of volatile chemical compounds in the target. Production yield curves are presented, and applications to other targets and elements are briefly discussed. (orig.)

[en] Targets made out of oxides of the alkaline earth metals have been shown at ISOLDE to be among the fastest targets for production of radioactive beams of the rare gas elements. In addition oxide target materials release nitrogen and seem to be the only ones which may release the element carbon due to its oxidation to the high temperature stable CO gas. Thick targets of MgO and CaO have been studied in connection with their use at the 1 GeV pulsed proton beam from the PS-BOOSTER synchrotron. It is shown that the 2.4 μs short proton pulse causes a pronounced bunched release with short delay of these elements which gives rise to 100-200 ms wide pulses of radioactive ion beams. Pulse shapes and overall yields of ion beams of He, Ne and Ar isotopes are studied as function of temperature and proton pulse intensity. For carbon and nitrogen also the release as function of the observed ionic species C⁺, CO⁺, N⁺ and N₂⁺ is discussed. (orig.)

[en] Published in summary form only

[en] The γ-rays following the β^- decay of ²²⁷Rn have been investigated by means of γ-ray singles and γγ-coincidence measurements using an array of 12 Compton-suppressed Ge detectors. The fast-timing βγγ(t) method has been used to measure six level lifetimes. Multipolarities of 32 transitions in ²²⁷Fr have been established by measuring conversion electrons with a mini-orange electron spectrometer. Most of the observed transitions have been placed in a level scheme comprising 38 excited states of ²²⁷Fr. The low-lying levels are interpreted in terms of seven rotational bands. The observed E1 strengths for two transitions connecting the K^π=3/2^± bands are consistent with the transitional character of ²²⁷Fr, and confirm the presence of octupole correlations in this nucleus. (orig.)

[en] The ⁶⁷Se and ⁶⁸Se isotopes near the proton drip line were produced by spallation of zirconium with 600 MeV protons at CERN. Beta decay properties were determined for the first time using the selectivity of molecular ion beams at the on-line mass separator ISOLDE. Chemically selective production was obtained through separation of the molecular ion COSe⁺. The half-lives of ⁶⁷Se and ⁶⁸Se were measured as 107±35 ms and 35.5±0.7 s respectively. From β-γ and γ-γ coincidences, and conversion-electron measurements, a decay scheme was obtained for ⁶⁸Se. For the ⁶⁸As ground state and several excited states, spin and parity are unambiguously determined from β-decay rates and electromagnetic multipolarity assignments. In addition to the strong Fermi branch between the mirror ground states of ⁶⁷Se and ⁶⁷As [J^π=(5/2)^-,T_z=±1/2], a GT branch to an excited state in ⁶⁷As is observed. Implications of ⁶⁷Se and ⁶⁸Se properties in the rp-process path are considered