Oinonen, M Äystö, J Jokinen, A Baumann, P Didierjean, François Huck, A Knipper, A Ramdhane, M Walter, G Van Duppen, P Huyse, M Marguier, G Novikov, Yu N Popov, A Seliverstov, D M Schatz, H Phys. Rev. C 10.1103/PhysRevC.61.035801 035801/1-5 61 3 2000 2000 The $\beta$-decay half-life of $^{70}$Kr has been measured for the first time at the ISOLDE PSB Facility at CERN. Mass separated $^{70}$Kr ions were produced by 1 GeV proton induced spallation reactions in a Nb foil. The measured half-life is 57(21) ms. This value is consistent with the half-life calculated assuming a pure Fermi decay, but is clearly lower than the value used in a recent rp-process reaction flow calculation. The result shows that the reaction flow via two-proton-capture of $^{68}$Se is 2.5 times faster than previously calculated assuming an astrophysical temperature of 1.5 GK and a density of 10$^{6}$g/cm$^{3}$. Georg, U Klein, A Neugart, R Neuroth, M Wilbert, S Lievens, P Vermeeren, L Brown, B A Keim, M Eur. Phys. J. A 31-40 8 1 2000 2000 The nuclear electric quadrupole moments of the isotopes $^{26}$Na, $^{27}$Na, $^{28}$Na and $^{29}$Na were measured by $\beta$-NMR spectroscopy in single crystals of LiNbO$_3$ and NaNO$_3$. High degrees of nuclear polarization were produced by optical pumping of the sodium atoms in a fast beam with a collinear laser beam.The polarized nuclei were implanted into the crystals and NMR signals were observed in the $\beta$-decay asymmetries. Preparatory measurements also yielded improved values for the magnetic moments of $^{27-31}$Na and confirmed the spin $I=3/2$for $^{31}$Na. The results are discussed in comparison with large-basis shell-model calculations. Kruglov, K Weissman, L Van den Bergh, P Andreyev, A Huyse, M Van Duppen, P Nucl. Instrum. Methods Phys. Res., A 10.1016/S0168-9002(99)01001-3 595-604 441 3 2000 2000 Modern experiments with secondary radioactive beams create new demands on beam diagnostics which has to provide on-line information on the low-intensity beams. We describe here a beam diagnostics system developed for the REX-ISOLDE facility (CERN), based on the observation of secondary electrons produced by a beam, impinging onto a foil. Results of tests with different beams of various energies and intensities are reported. (21 refs). Kellerbauer, A G Kim, T Moore, R B Varfalvy, P Nucl. Instrum. Methods Phys. Res., A 10.1016/S0168-9002(01)00286-8 276-285 469 2001 2001 The cooling action of a buffer gas on ions contained within it can be used to cool an ion beam, thereby greatly improving its emittance and energy spread. It can also be used to greatly enhance the collection of an ion beam in an electromagnetic trap. The basic principles will be introduced in the context of the development of a system for cooling ISOLDE beams for the ISOLTRAP facility. Herfurth, F. Dilling, J. Kellerbauer, A. Bollen, G. Henry, S. Kluge, H.-J. Lamour, E. Lunney, D. Moore, R.B. Scheidenberger, C. Schwarz, S. Sikler, G. Szerypo, J. Nucl. Instrum. Methods Phys. Res., A 10.1016/S0168-9002(01)00168-1 254-275 469 2001 2001 An ion beam cooler and buncher has been developed for the manipulation of radioactive ion beams. The gas-filled linear radiofrequency ion trap system is installed at the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN. Its purpose is toaccumulate the 60-keV continuous ISOLDE ion beam with high efficiency and to convert it into low-energy low-emittance ion pulses. The efficiency was found to exceed 10\,\% in agreement with simulations. A more than 10-fold reduction of the ISOLDE beam emittance can be achieved. The system has been used successfully for first on-line experiments. Its principle, setup and performance will be discussed. Nummela, S Baumann, P Caurier, E Dessagne, P Jokinen, A Knipper, A Le Scornet, G Miehé, C Nowacki, F Oinonen, M Radivojevic, Z Ramdhane, M Walter, G Äystö, J Phys. Rev. C 10.1103/PhysRevC.63.044316 044316/1-11 63 4 2001 2001 The $^{34,35}Al\beta$ decays were studied at the CERN on-line mass separator ISOLDE by $\beta-\gamma, \beta-\gamma-\gamma$ and $\beta-n-\gamma$ measurements, in order to corroborate thelow-level description of $^{34}Si$ and to obtain the first information on the level structure of the N=21 isotope $^{35}Si$. Earlier observed $\gamma$ lines in $^{34} Al$ decay were confirmed and new gamma transitions following both beta decay and $\beta$-delayed neutron emission were established. The first level scheme in $^{35}Si$, including three excited states at 910, 974 and 2168 keV, is consistent with $J^{\pi} =3/2^{-}$ and $3/2^{+}$ for the first two states respectively. Beta-decay half-life of $T_{1/2} = 38.6 (4)$ ms and beta-delayed neutron branching $P_{n}$ value $(P_{n} =41(13) %)$ were measured unambiguously. The significance of the single-particle energy determination at N=21, Z=14, for assessing the effective interaction in sd-fp shell-model calculations, is discussed and illustrated by predictions for different n-rich isotopes. Dietrich, M Burchard, A Degering, D Deicher, M Kortus, J Magerle, R Möller, A Samokhvalov, V Unterricker, S Vianden, R Z. Naturforsch. A 256-60 55 1-2 2000 2000 Electric field gradients have been measured at substitutional lattice sites in ternary semiconductors using perturbed gamma - gamma angular correlation spectroscopy. The experimental results for A/sup I/B/sup III/C/sub 2//sup VI/ chalcopyrite structure compounds and Square Operator A/sup II/B/sub 2//sup III/C/sub 4//sup VI/ defect chalcopyrites are compared with ab-initio calculations. The latter were carried out with the WIEN code that uses the full potential linearized augmented plane wave method within a density functional theory. The agreement between experiment and theory is in most cases very good. Furthermore, the anion displacements in AgGaX/sub 2/- compounds (X: S, Se, Te) have been determined theoretically by determining the minimum of the total energy of the electrons in an elementary cell. (20 refs). Nucl. Instrum. Methods Phys. Res., B 10.1016/S0168-583X(99)00552-2 528-35 160 4 2000 2000 Radioactive copper isotopes were ionized with the resonance ionization laser ion source at the on-line isotope separator ISOLDE (CERN). Using the different hyperfine structure in the 3d/sup 10/ 4s /sup 2/S/sub 1/2/-3d/sup 10/ 4p /sup 2/P/sub 1/2//sup 0/ transition the low- and high-spin isomers of /sup 70/Cu were selectively enhanced by tuning the laser wavelength. The light was provided by a narrow-bandwidth dye laser pumped by copper vapor lasers and frequency doubled in a BBO crystal. The ground state to isomeric state intensity ratio could be varied by a factor of 30, allowing to assign gamma transitions unambiguously to the decay of the individual isomers. It is shown that the method can also be used to determine magnetic moments. In a first experiment for the 1/sup +/ ground state of /sup 70/Cu a magnetic moment of (+)1.8(3) mu /sub N/ and for the high-spin isomer of /sup 70/Cu a magnetic moment of (+or-)1.2(3) mu /sub N/ could be deduced. (20 refs). Nilsson, T AIP Conf. Proc. 10.1063/1.1395300 265-268 576 2001 2001 The ISOLDE facility at CERN has been producing a broad range of radioactive beams for more than 30 years. The present low-energy beams (60 keV) of ISOLDE will soon be complemented by a post- accelerator, REX-ISOLDE, currently under construction. A novel scheme of trapping, cooling and charge-state breeding has been devised, which allows for a short, cost-effective linac reaching 0.8-2.2 MeV /u. The original physics aim of the REX-ISOLDE experiment is to probe the weakening of the magic numbers N=20,28 when going to extremely neutron-rich species by Coulomb excitation and neutron transfer reactions. For this purpose, a highly efficient Ge-detector array will be used, the MINIBALL. A number of other experiments are as well approved or planned. (14 refs). Beck, D Ames, F Audi, G Eur. Phys. J. A 10.1007/s100500070085 307-29 8 3 2000 2000 Ríkovská, J Stone, N J Van Esbroeck, K White, G Wöhr, A Veskovic, M Towner, I S Mantica, P F Prisciandaro, J I Morrissey, D J Fedosseev, V Mishin, V I Köster, U Walters, W B Giles, T Phys. Rev. Lett. 1392-1395 85 2000 2000 The first fully on-line use of the angular distribution of $\beta$ - emission in detection of NMR of nuclei oriented at low temperatures is reported. The magnetic moments of the single valence particle, intermediate mass, isotopes $^{67}$Ni($\nu{p}^{-1}_{1/2}$; 1/2$^{-}$) and $^{69}$Cu($\pi{p}^{+1}_{ 3/2}$; 3/2$^{-}$) are measured to be +0.601(5)$\mu_{N}$ and +2.84(1)$\mu_{N}$ respectively, revealing only a small deviation from the neutron $p_{1/2}$ single-particle value in the former and a large deviation from the proton $p_{3/2}$ single-particle value in the latter. Quantitative interpretation is given in terms of core polarization and meson-exchange currents. Ronning, C R Dalmer, M Uhrmacher, M Restle, M Vetter, U Ziegeler, L Hofsäss, H C Gehrke, T Järrendahl, K Davis, R F J. Appl. Phys. 10.1063/1.372154 2149-2157 87 5 2000 2000 Hamann, J Burchard, A Deicher, M Filz, T Lany, S Ostheimer, V Strasser, F Wolf, H Wichert, T J. Cryst. Growth 10.1016/S0022-0248(00)00083-X 207-11 214-215 2000 2000 Nominally undoped ZnTe and CdTe crystals were implanted with radioactive /sup 111/Ag, which decays to /sup 111/Cd, and investigated by photoluminescence spectroscopy (PL). In ZnTe, the PL lines caused by an acceptor level at 121 meV are observed: the principal bound exciton (PBE) line, the donor-acceptor pair (DAP) band, and the two-hole transition lines. In CdTe, the PBE line and the DAP band that correspond to an acceptor level at 108 meV appear. Since the intensities of all these PL lines decrease in good agreement with the half-life of /sup 111/Ag of 178.8 h, both acceptor levels are concluded to be associated with defects containing a single Ag atom. Therefore, the earlier assignments to substitutional Ag on Zn- and Cd-lattice sites in the respective II-VI semiconductors are confirmed. The assignments in the literature of the S/sub 1/, S /sub 2/, and S/sub 3/ lines in ZnTe and the X/sub 1//sup Ag/, X/sub 2 //sup Ag//C/sub 1//sup Ag/, and C/sub 2//sup Ag/ lines in CdTe to Ag- related defect complexes are not confirmed. (16 refs). Lhersonneau, G. Wohr, A. Pfeiffer, B. Kratz, K.L. Phys. Rev. C 10.1103/PhysRevC.63.034316 034316 63 2001 2001 The decay of the mass-separated, very neutron-rich isotope Br-93 has been studied by gamma-spectroscopy. A level scheme of its daughter Kr-93 has been constructed. Level energies, gamma-ray branching ratios and multipolarities suggest spins and parities which are in accord with a smooth systematics of the N=57 isotones for Z less-equal 40, suggesting the N=56 shell closure still to be effective in Kr isotopes. So far, there is no indication of a progressive onset of deformation in neutron-rich Kr isotopes. García-Borge, M J Axelsson, L Äystö, J Bergmann, U C Fraile-Prieto, L M Honkanen, J A Hornshøj, P Jading, Y Jokinen, A Jonson, B Martel, I Mukha, I Nilsson, T Nyman, G H Oinonen, M Piqueras, I Riisager, K Siiskonen, T Smedberg, M H Tengblad, O Thaysen, J Wenander, F Fynbo, H O U Nucl. Phys. A 10.1016/S0375-9474(00)00248-7 38-60 677 1-4 2000 2000 We have measured the $\beta$-decay of $^{31}$Ar with a high granularity setup sensitive to multiparticle decay branches. Two-proton emission is observed from the isobaric analog state in $^{31}$Cl to the four lowest states in $^{29}$P and furthermore from a large number of states fed in Gamow-Teller transitions. The mechanism of two-proton emission is studied via energy and angular correlations between the two protons. In all cases the mechanism is found to be sequential yielding information about states in $^{30}$S up to 8 MeV excitation energy. Improved data on the $\beta$-delayed one-proton branches together with the two-proton data provide precise information about the $\beta$-strength distribution up to 15 MeV excitation energy. (44 refs). Herfurth, F Dilling, J Kellerbauer, A G Audi, G Beck, D Bollen, G Henry, S Kluge, H J Lunney, M D Moore, R B Scheidenberger, C Schwarz, S Sikler, G Szerypo, J Phys. Rev. Lett. 10.1103/PhysRevLett.87.142501 142501 87 2001 2001 Mass measurements on $^{33, 34, 42, 43}$Ar were performed using the Penning trap mass spectrometer ISOLTRAP and a newly constructed linear Paul trap. This arrangement allowed for the first time to extend Penning trap mass measurements to nuclides with half-lives below one second ($^{33}$Ar: T$_{1/2}$ =174 ms). A mass accuracy of about $10^{-7}$ ($\delta m \approx 4$ keV) was achieved for all investigated nuclides. The isobaric multiplet mass equation (IMME) was checked for the $A=33$, $T=3/2$ quartet and found to be inconsistent with the generally accepted quadratic form. Kratz, K L Nucl. Phys. A 10.1016/S0375-9474(01)00719-9 308-17 688 1-2 2001 2001 Progress in the astrophysical understanding of r-process nucleosynthesis also depends on the knowledge of nuclear-physics quantities of extremely neutron-rich isotopes. In this context, experiments at CERN-ISOLDE have played a pioneering role in exploring new shell-structure far from stability. Possible implications of new nuclear-data input on the reproduction of r-abundance observations are presented. Lhersonneau, G. Pfeiffer, B. Gabelmann, H. Kratz, K.L. Phys. Rev. C 10.1103/PhysRevC.63.054302 054302 63 2001 2001 The decay of the very neutron-rich nucleus Rb-100 has been studied by gamma-spectroscopy of on-line mass-separated samples. Schemes for beta-decay to Sr-100 and beta-n-decay to Sr-99 are presented. New sets of transitions in Sr-99 and Sr-100 with identical energies are observed. All identical bands so far observed in neutron-rich Sr isotopes obey a simple energy rule valid for even-even, odd-even and odd-odd bands. Correia, J G Capponi, J J Ctortecka, B Butz, T Tröger, W Araújo, J P Loureiro, S M Toulemonde, P Gatt, R Le Floc'h, S Bordet, P Phys. Rev. B 10.1103/PhysRevB.61.11769 11769-11775 61 2000 2000 Electric-field gradients on mercury sites of the HgBa$_{2}$CuO$_{4+\delta}$ high-$T_{C}$ superconductor were measured with the perturbed angular correlation technique and interpreted with $\textit{ab initio}$ calculations. Under oxygen annealing, an asymmetric electric-field gradient has been assigned to the presence of single oxygen atoms, O$_{\delta}$ , which are located in the Hg planes. These experiments provide an atomic scale tool for studying charge-density variations occuring in the neighborhood of the Hg atoms, which can be induced, particularly, by pointlike defects. Correia, J G Araújo, J P Marques, J G Ramos, A R Lourenço, A A Amaral, V S Galindo, V Senateur, J P Weiss, F Wahl, U Melo, A A Soares, J C Sousa, J B Hyperfine Interact. 10.1023/A:1012653614899 461-473 129 2000 2000 Recent results on the study of high-T$_{c}$ superconductors using the e$^-\!-\gamma$ perturbed angular correlation technique are presented. The basic features of the experimental equipment and its installation at the ISOLDE facility are briefly described. Results obtained from $^{197m}$Hg implanted into high quality Y$_{1}$Ba$_{2}$Cu$_{3}$O$_{6+\delta}$ epitaxy thin films are presented and discussed. Araújo, J P Correia, J G Amaral, V S Tavares, P B Lencart-Silva, F Lourenço, A A Sousa, J B Vieira, J M Soares, J C 2000 2000 Although Cd and Ca ions have the same valence and cation size, their incorporation into vacancy doped La manganites induce different properties. While the incorporation of Ca leads to high Tc up to 250 K and induces a metallic-like behaviour, the incorporation of Cd severely reduces Tc and promotes insulator-like behaviour. In this work, the Cd hyperfine fields have been measured with the Perturbed Angular Correlations (PAC) technique after implantation and annealing of $^{111m}$Cd in La-Cd-MnO$_3$ samples. The PAC results are compared with measurements of the resistivity and magnetisation performed on the same samples. The mixed La and Mn site Cd occupancy is suggested as a possibility to explain the properties of the La-Cd-MnO$_3$ system. Correia, J G Araújo, J P Loureiro, S M Toulemonde, P Le Floc'h, S Bordet, P Capponi, J J Gatt, R Tröger, W Ctortecka, B Butz, T Haas, H Marques, J G Soares, J C Physica C 1969-1972 341-348 2000 2000 Electric field gradients (EFG) on mercury sites of the Hg1201 high-TC superconductors were measured with the perturbed angular correlation (PAC) technique. In Hg1201 samples where PAC detects higher oxygen content the EFGs have decreased to lower values indicating an elongation of the Hg-apical oxygen dumb-bell. On the same samples the asymmetry parameter of the EFG becomes non-zero below 100 K, showing that the charge distribution near the Hg-apical oxygen chain becomes non-axially symmetric at low temperature. Köster, U Nucl. Phys. A 10.1016/S0375-9474(01)01625-6 441-451 701 2002 2002 The three main requirements to the ion source of an ISOL facility are efficiency, selectivity and rapidity. For many metallic elements these requirements are ideally fulfilled by a resonance ionization laser ion source (RILIS). Presently such ion sources are used at the RIB facilities IRIS (Gatchina), ISOLDE (CERN), LISOL (Leuven), TIARA (Takasaki) and IMP (Lanzhou) to provide beams with low isobaric contamination. The isotopically pure beams enabled to make spectacular progress, for instance in nuclear spectroscopy of very rare isotopes. The scanning of the hyperfine structure with a small bandwidth laser allows moreover to separate individual isomers. The RILIS has also been used as a sensitive tool for atomic spectroscopy (measurement of the isotope shift and of nuclear moments) of exotic isotopes. Oinonen, M Äystö, J Köster, U Huikari, J Jokinen, A Nieminen, A Peräjärvi, K Baumann, P Didierjean, François Huck, A Knipper, A Ramdhane, M Walter, G Huyse, M Van Duppen, P Marguier, G Novikov, Yu N Popov, A Seliverstov, D M Schatz, H Nucl. Phys. A 613-620 701 2002 2002 Bergmann, U C Axelsson, L Bennett, J R J García-Borge, M J Catherall, R Drumm, P V Fedosseev, V Forssén, C Fraile-Prieto, L M Fynbo, H O U Georg, U Giles, T Grévy, S Hornshøj, P Jonson, B Jonsson, O C Köster, U Lettry, Jacques Markenroth, K G Marqués, F M Mishin, V I Mukha, I Nilsson, T Nyman, G H Oberstedt, A Ravn, H L Riisager, K Schrieder, G Sebastian, V Simon, H Tengblad, O Wenander, F Wilhelmsen-Rolander, K Nucl. Phys. A 10.1016/S0375-9474(01)01611-6 363-368 701 2002 2002 This paper is divided in three parts. (i) The measurement of yields and decay losses of Li and Be isotopes released from a thin foil tantalum target at the CERN/ISOLDE PS-Booster. (ii) Results from $\beta$-decay experiments on $^{12}$Be and $^{14}$Be. An improved half-life of 21.49(3)~ms has been obtained for $^{12}$Be. (iii) The $\beta$-decay of $^{9}$C. An outline of the analysis procedure to determine the branching at high excitation energies is given. The ground-state branch has been determined to 54.1(15)%. Nilsson, T Nyman, G H Riisager, K Hyperfine Interact. 67-81 129 1-4 2000 2000 Nuclear halo states are studied experimentally with a wide range of techniques. We review the results coming from ISOLDE, emphasizing the $\beta$-decay experiments. Some general comments on the role of $\beta$-decays for halo research are given. We outline the possibilities for low-energy reaction experiments arising from REX-ISOLDE.