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The difference in isotope production between 1 and 1.4 GeV proton projectiles was investigated at ISOLDE/CERN during the year 1999. As target materials uranium carbide, thorium carbide, lead and lanthanum oxide were used and the ratio of the measured production yields for the two different projectile energies were determined for isotopes of the elements francium, mercury, thallium, xenon, cesium, krypton, rubidium and neon. A comparison of these experimental results with the predictions from a two-step reaction model Monte-Carlo code shows good agreement. (C) 2002 Elsevier Science B.V. All rights reserved.

Using β-radiation detected nuclear magnetic resonance (β-NMR), we investigated the microscopic behavior of implanted 8 Li in nominally undoped ZnSe crystals. From the temperature-dependent amplitudes of high-resolution NMR spectra we conclude a gradual interstitial-to-substitutional site change between 200 and 350 K . This is in accordance with earlier emission channeling results. We argue that this conversion proceeds via Lii++VZn2−→LiZn− and involves implantation related Zn vacancies.

Short-lived radioisotopes are element selectively ionized by the resonance ionization laser ion source (RILIS) of the on-line isotope separator ISOLDE (CERN). The relative production of low and high spin isomers can be significantly changed when a narrow-bandwidth laser is used to scan through the atomic hyperfine structure. This allows the assignment of gamma ray transitions to the decay of the individual isomers. Moreover, the measurement of the hyperfine splitting provides a very sensitive method for the determination of magnetic moments of exotic isotopes. The technical developments are discussed for the example of copper.

Experiments using laser spectroscopy and nuclear magnetic resonance techniques have been performed at ISOLDE on the unstable isotopes of several light elements. The results include nuclear ground state spins, magnetic dipole and electric quadrupole moments, and the behaviour of mean square nuclear charge radii within isotopic strings. These give important information about the nuclear structure at shell closures and close to the drip lines.

β-active probe nuclei are implanted in nominally undoped ZnSe crystals. β-radiation detected nuclear magnetic resonance (β-NMR) studies are described for two different probe nuclei, 8Li and 12B. This way, the implantation behavior of two “opposite”dopants, one acceptor (Li) and one donor (B) can be characterized by the same microscopic technique. Such characterizations are attempted in terms of the structure of intermediate or final lattice sites, defect charge states, or the kinetics of defect reactions and site changes.

Hyperfine separations in unstable ${\mathrm{Eu}}^{+}$ ions of mass 148, 149, and 150 have been measured in laser-microwave double-resonance experiments in a Paul ion trap. In spite of the small available quantities of the isotopes, the experimental uncertainties are of the order of ${10}^{\ensuremath{-}8}$ or below, which is of the same order as in earlier measurements on stable isotopes of ${\mathrm{Eu}}^{+}.$ Extensive second-order perturbation calculation is required to obtain coupling constants for magnetic-dipole $(A)$ and electric-quadrupole $(B)$ interactions. The uncertainties are a few times ${10}^{\ensuremath{-}7}$ for $A$ and ${10}^{\ensuremath{-}3}$ for $B.$ The experiments are a step in an attempt to determine the differential hyperfine anomaly (Bohr-Weisskopf effect) in a long chain of isotopes.

We report on the measurement of optical isotope shifts for $^{32-40}$Ar and for $^{46}$Ar from which the changes in mean square nuclear charge radii across the N = 20 neutron shell closure are deducted. The investigations were carried out by collinear laser spectroscopy in fast beams of neutral argon atoms. The ultra-sensitive detection combines optical pumping, state-selective collisional ionization and counting of $\beta$-radioactivity. By reaching far into the sd-shell, the results add new information to the systematics of radii in the calcium region (Z $\approx$ 20). Contrary to all major neutron shell closures with N $\geq$ 28, the N = 20 shell closure causes no significant slope change in the development of the radii. Information from the hyperfine structure of the odd-A isotopes includes includes the magnetic moments of $^{33}$Ar (I=1/2) and $^{39}$Ar (I=7/2), and the quadrupole moments of $^{35}$Ar, $^{37}$Ar (I=3/2) and $^{39}$Ar. The electromagnetic moments are compared to shell-model predictions for the sd- and fp-shell. Even far from stability a very good agreement between experiment and theory is found for these quantities. The mean square charge radii are discussed in the framework of spherical SGII Skyrme-type Hartree-Fock calculations.

The spins, moments and radii of krypton isotopes have been investigated by collinear fast-beam laser spectroscopy in combination with ultra-sensitive collisional ionization detection. The sequence of isotopes under study ranges from the neutron-deficient N = Z = 36 isotope 72 Kr to the neutron-rich 96 Kr ( N = 60). The mean-square charge radii in the neighbourhood of the N = 50 neutron-shell closure exhibit a pronounced shell effect which has recently been explained in the framework of relativistic mean-field theory. The results for the neutron-deficient nuclei are related to the shape coexistence of strongly prolate and near-spherical states which is known from nuclear spectroscopy. Here, an inversion of the odd-even staggering is observed below the neutron number N = 45. The neutron-rich transitional nuclei are influenced by the N = 56 subshell closure. In contrast to the N = 60 isotones 97 Rb, 98 Sr and 100 Zr, the new isotope 96 Kr is not strongly deformed.

Radioactive copper isotopes were ionized with the resonance ionization laser ion source (RILIS) at the on-line isotope separator ISOLDE (CERN). Using the different hyperfine structure in the 3d10 4s 2 S1/2 – 3d10 4p 2 P01/2 transition the low- and high-spin isomers of 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 (CVL) 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+ ground state of 70 Cu a magnetic moment of (+)1.8(3) μN and for the high-spin isomer of 70 Cu a magnetic moment of (±)1.2(3) μN could be deduced.

Fast-beam collinear laser spectroscopy with resonance detection by counting of fluorescence photons provides a versatile tool for precise determinations of nuclear ground-state properties. The intrinsic high sensitivity of this method can be further increased by almost three orders of magnitude if measuring schemes based on ion or atom counting are introduced. The optical pumping from one atomic state to another at an appreciably different excitation energy is detected via state-selective collisional charge exchange processes and charge-state separated atom or ion counting. Applications of these techniques on alkaline earth, noble gas, mercury and thallium beams is examined.

α-Alkylated azocane-2-carboxylic acid methyl esters 5 were synthesized with excellent enantiomeric excess (>96%) in four steps starting from optically active β-keto esters 1 . The synthesis involved tetrazole formation, reduction, protection, and oxidation.

A {beta}-decay study of {sup 77}Cu has been performed at the ISOLDE mass separator with the aim to deduce its {beta}-decay properties and to obtain spectroscopic information on {sup 77}Zn. Neutron-rich copper isotopes were produced by means of proton- or neutron-induced fission reactions on {sup 238}U. After the production, {sup 77}Cu was selectively laser ionized, mass separated, and sent to different detection systems where {beta}-{gamma} and {beta}-n coincidence data were collected. We report on the deduced half-live, decay scheme, and possible spin assignment of {sup 77}Cu.

The {beta}-decay properties of {sub 28}{sup 72}Ni{sub 44} and {sub 29}{sup 72}Cu{sub 43} have been studied at the LISOL facility of Louvain-La-Neuve and at the CERN-ISOLDE facility, respectively. These neutron-rich nuclei have been produced in the proton-induced fission of {sup 238}U. Their decay schemes are presented and the lifetime T{sub 1/2}=6.63(3) s of {sup 72}Cu was measured. No {beta}-decaying isomeric state was found in {sup 72}Cu, in line with a suggested spin (2) for its ground state. Spin and parity assignments of the observed excited states in the odd-odd nucleus {sup 72}Cu are proposed and discussed in terms of coupling between the valence proton and neutrons. Comparison is made with a schematic shell-model picture of {sup 72}Cu and with large-scale shell-model calculations performed in the (2p{sub 3/2}1f{sub 5/2}2p{sub 1/2}1g{sub 9/2}) shell space outside the doubly magic {sub 28}{sup 56}Ni{sub 28} core.

A \ensuremath{\beta}-decay study of the even mass $^{74,76,78}\mathrm{Cu}$ isotopes toward levels in $^{74,76,78}\mathrm{Zn}$ was performed at the ISOLDE mass separator. The copper isotopes were produced in proton- or neutron-induced fission reactions on $^{238}\mathrm{U}$, laser ionized, mass separated, and sent to a $\ensuremath{\beta}\ensuremath{-}\ensuremath{\gamma}$ detection system. Half-lives, decay schemes, and possible spin configurations were obtained for the copper isotopes. The results are compared with calculations using schematic forces as well as large-scale shell-model calculations with realistic forces.

NESTER; International audience; The neutron-rich nuclei $^{72}$Ni and $^{72}$Cu have been produced in the proton-induced fission of $^{238}$U at the LISOL and ISOLDE facilities of Louvain-La-Neuve and CERN. Partial beta-decay schemes are presented, giving some information about the nuclear structure of their daughter nuclei $^{72}$Cu and $^{72}$Zn. The lifetime of $^{72}$Cu was determined to be $T_1/2$ = 6.63(3) s, in line with previous measurements. No $\beta$-decaying isomeric states were identified in $^{72}$Cu, in contrast to $^{70}$Cu. The spin and the parity of several states in $^{72}$Cu are tentatively assigned and a comparison is made with different shell-model predictions.

The 70Ni nucleus has been produced at the LISOL facility and its beta decay to 70Cu has been observed. In parallel, the 70Cu nucleus has been produced at the ISOLDE facility. A new third beta-decaying isomeric state in 70Cu has been identified, partly with the aid of the in-source laser spectroscopy method. Its measured half-life is T1/2=33(2) s. In addition, two isomeric transitions in 70Cu have been observed at energies of 101.1(3) and 141.3(3) keV, and it allowed the relative placement of the three 70Cu isomeric states and their tentative spin and parity assignments. The new 70Cu isomer was found to be weakly populated in the beta decay of 70Ni. It allowed the construction of the 70Ni decay scheme. Furthermore, the beta decay of the three 70Cu isomers to 70Zn has been measured and their decay schemes are presented. The 70Ni beta decay to the isomeric states in 70Cu and their subsequent isomeric decay and beta decay to 70Zn are discussed within the extreme shell-model picture of two valence nucleons outside the semidouble magic 2868Ni40 core and it yields satisfactory results. Large-basis shell-model calculations using 2856Ni28 as the core and a realistic effective interaction support rather well the suggested interpretation. (Less)

Several scientific committees, such as NUPECC [1], have established that neutron-rich beams will provide a wealth of new opportunities for nuclear physics studies. The proton-induced fission of actinide material is a proven mechanism for the production of neutron-rich nuclei, but, within the Eurisol project [2], new innovations are being tested with the goal of increasing current fission rates by three orders of magnitude.

Nuclides in the vicinity of the doubly magic 78Ni nucleus are ideal test cases for the nuclear shell model [1,2]. Still, experimental data in this region is rather scarce because of experimental limitations. In this contribution we report the first observation of the β-decay of 78Cu, only one proton and one neutron hole away from 78Ni.

The energy dependence of production yields for Kr and Cs isotopes has been investigated with 600 MeV, 1 GeV and 1.4 GeV protons.

Radioactive ion beam intensities have been measured at ISOL (isotope separation on-line) facilities from many different targets, but only rarely these intensities are converted into production cross-sections. Here we discuss the method and possible problems in this conversion at the examples of Kr and Xe produced by 1.4 GeV-proton-induced fission of 238U at ISOLDE and Rb and Cs produced by approx. 10 MeV-neutron-induced fission of 238U at PARRNe.

Many elements are rapidly released from oxide matrices. Some oxide powder targets show a fast sintering, thus losing their favorable release characteristics. Loosely packed oxide fiber targets are less critical since they may maintain their open structure even when starting to fuse together at some contact points. The experience with various oxide fiber targets (titania, zirconia, ceria and thoria) used in the last years at ISOLDE is reviewed. For short-lived isotopes of Cu, Ga and Xe the zirconia and ceria targets respectively provided significantly higher yields than any other target (metal foils, oxide powders, etc.) tested before. Titania fibers, which were not commercially available, were produced in a relic process by impregnation of a rayon felt in a titanium chloride solution and subsequent calcination by heating the dried felt in air. Thoria fibers were obtained either by the same process or by burning commercial gas lantern mantle cloth. In the future a beryllia fiber target could be used to produce very intense 6He beams (order of 1013 ions per second) via the 9Be(n,α) reaction using spallation neutrons.

The ISOLDE pulsed proton beam peak power amounts to 500 MW during the 2.4 μs proton pulse. The fraction of the proton pulse energy deposited in the target material is at the origin of severe thermal shocks. Quantitative measurement of their effect on the release of radioelements from ISOLDE targets was obtained by comparison of release profiles measured under different proton beam settings. The thermal shock induced in liquids (Pb, Sn, La) lead to mechanical failure of ISOLDE molten metal target vessels. Failure analysis is presented and discussed in the light of the response of mercury samples submitted to the ISOLDE beam and monitored by high-speed optical systems.

The chemical selectivity of the target and ion-source production system is an asset for radioactive ion-beam (RIB) facilities equipped with mass separators. Ionization via laser induced multiple resonant steps has such selectivity. However, the selectivity of the ISOLDE resonant ionization laser ion-source (RILIS), where ionization takes place within high temperature refractory metal cavities, suffers from unwanted surface ionization of low ionization potential alkalis. In order to reduce this type of isobaric contaminant, surface ionization within the target vessel was used. On-line measurements of the efficiency of this method is reported, suppression factors of alkalis up to an order of magnitude were measured as a function of their ionization potential. The time distribution of the ion-bunches produced with the RILIS was measured for a variety of elements and high temperature cavity materials. While all ions are produced within a few nanoseconds, the ion-bunch sometimes spreads over more than 100 μs. This demonstrates that ions are confined within high temperature metallic cavities. It is the internal electrical field of these cavities that causes the ions to drifts to the extraction region and defines the dwell time of the ions in the cavity. Beam optics calculations were carried out to simulate the pulse shape of a RILIS ion-bunch and are compared to the actual measurements.

ISOLDE’s high-resolution isotope separator was recomissioned in mid 2000, after a period out of service. Since then the separator has routinely run with a mass resolution of 3000–4500, and during 2001 it delivered 72% of ISOLDE’s radioactive output. A concerted effort has been made to understand the ion optics and optimise performance. In this paper we present an overview of the HRS, and investigate the factors which limit the attainable mass resolution: ion-source emittance, optical aberrations, beam instrumentation and magnet stability.

The ISOLDE resonance ionization laser ion source (RILIS) allows to ionize efficiently and selectively many metallic elements. In recent yield surveys and on-line experiments with the ISOLDE RILIS we observed 23–34 Mg, 26–34 Al, 98–132 Cd, 149 Tb, 155–177 Yb, 179–200 Tl, 183–215 Pb and 188–218 Bi. The obtained yields are presented together with measured release parameters which allow to extrapolate the release efficiency towards more exotic (short-lived) nuclides of the same elements. 2002 Elsevier Science B.V. All rights reserved.

We have obtained information on the atomic hyperfine splitting and, hence, on magnetic moments in neutron-rich ${}^{68,70}\mathrm{Cu}$ isotopes by scanning the frequency of the narrow-band laser of the first excitation step in the resonance ionization laser ion source. The deduced magnetic moments are $\ensuremath{\mu}{(}^{68}{\mathrm{Cu}}^{g}{,I}^{\ensuremath{\pi}}{=1}^{+})=+2.48(2)(7){\ensuremath{\mu}}_{N},$ $\ensuremath{\mu}{(}^{68}{\mathrm{Cu}}^{m}{,I}^{\ensuremath{\pi}}{=6}^{\ensuremath{-}})=+1.24(4)(6){\ensuremath{\mu}}_{N},$ and $\ensuremath{\mu}{(}^{70}{\mathrm{Cu}}^{{m}_{2}}{,I}^{\ensuremath{\pi}}{=1}^{+})=+1.86(4)(6){\ensuremath{\mu}}_{N},$ $\ensuremath{\mu}{[}^{70}{\mathrm{Cu}}^{g}{,I}^{\ensuremath{\pi}}{=(6}^{\ensuremath{-}})]=(+)1.50(7)(8){\ensuremath{\mu}}_{N}.$ The results of the scans analysis points out the existence of a new isomer, ${}^{70}{\mathrm{Cu}}^{{m}_{1}}.$ Its deduced magnetic moment is $(\ensuremath{-})3.50(7)(11){\ensuremath{\mu}}_{N},$ in good agreement with the ${I}^{\ensuremath{\pi}}{=3}^{\ensuremath{-}}$ assignment. The method of in-source atomic spectroscopy, as well as the analysis of the obtained data, is described. The results are discussed in terms of single-particle configurations coupled to the ${}^{68}\mathrm{Ni}$ core.

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 Be-12 and Be-14, an improved half-life of 21.49(3) ms has been obtained for Be-12; (iii) the beta-decay of C-9. 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)%.

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.

At the on-line mass separator facility ISOLDE ion beams of radioactive isotopes are produced by nuclear reactions induced by bombardment of thick targets with a 1 GeV pulsed proton beam. With the use of a large variety of target materials and ion sources over 600 isotopes of more than 60 elements (Z=2 to 88) have been produced up to now. This great choice offers amplitude of possibilities for experiments in nuclear physics, atomic physics, nuclear solid state physics, nuclear astrophysics, biophysics, nuclear medicine and even particle physics. A variety of new results have been obtained during the last year like the magnetic moment of 11Be, the beta delayed charged particle emission of 9C, high precision mass measurements with an accuracy up to 10−7, the half life of the waiting point nucleus 129Ag, the direct observation of the diffusion of free hydrogen in III-V semiconductors and monolayer-resolved measurements in ultrathin magnetic multilayers.

Since the move of ISOLDE from CERN’s synchrocyclotron (SC) to the Proton Synchrotron Booster (PSB) in 1992 extensive work has been devoted to the development of new beams, i.e. the production of new isotopes, beams of higher intensity and the ionization of further elements. Most of these developments were driven by the particular needs of the physics community proposing new experiments. The main achievements were the adaption of liquid metal targets to the pulsed proton beam to prevent shockwaves and splashing inside the target container and systematic studies on the time structure of the release of the isotopes from the target. Furthermore the work on laser ion-sources already started at ISOLDE-2 was continued, the so-called RIST target was developed, and most recently first tests on the isotope production while increasing the proton energy from 1 GeV to 1.4 GeV were done. The latter topics are discussed in this paper.

The quadrupole moments of the neutron-rich isotopes {sup 26-31}Na and of the neutron-deficient {sup 20}Na were measured by {beta}-NMR after implantation of the short-lived nuclei into the host crystal lattices of Mg, LiNbO{sub 3} and NaNO{sub 3}. The ion beams from ISOLDE were neutralized and polarized by in-beam optical pumping. Of particular interest are the isotopes close to N=20 for which various experimental observations suggest rather strong deformation.

At the ISOLDE facility radioactive ion beams are produced via proton induced reactions in a target which is connected to a laser ion source. For beryllium a two step excitation scheme with laser light at wavelengths of λ=235 nm and λ=297 nm has been developed. Efficient laser ionization of beryllium was achieved with a new optical set-up using frequency tripling with two non-linear BBO crystals to generate laser light in the ultraviolet for the first excitation step. The second step was optimized to reach the 2p2 1S0 autoionizing state for high ionization efficiency. The isotope shift of 7,9,10,11,12,14Be could be measured by tuning the wavelength of the first step. The laser ion source has also been used for the preparation of neutron-rich silver ion beams. Tuning the laser frequency of the first step it was possible to ionize selectively low-and high spin isomers of silver isotopes via the hyperfine structure. In both cases it was demonstrated that laser spectroscopy of exotic isotopes can be performed ...

Isotope shifts and hyperfine structures of the 205,206,208,210,210m,212,213 Bi isotopes have been studied on the 306.7 nm line using gas cell laser spectroscopy. The neutron-rich isotopes are the first isotones of Pb to be measured immediately above the N = 126 shell closure. The ground state quadrupole moments of the even- N isotopes increase as neutrons are added or removed from the N = 126 shell, but no corresponding increase is observed in the charge radii.

The nuclear quadrupole moments of neutron-rich sodium isotopes are being investigated with the help of in-beam polarization by optical pumping in combination with $\beta$-NMR techniques. First measurements have yielded the quadrupole splittings of NMR signals in the lattice of LiNbO$_{3}$ for the isotopes $^{26}$Na, $^{27}$Na and $^{28}$Na. Interaction constants and ratios of the electric quadrupole moments are derived. In view of future experiments, $\beta$-decay asymmetries for the sequence of isotopes up to the $N$=20 neutron shell closure, $^{26-31}$Na, have been measured.

Collinear laser spectroscopy experiments in the LuI transition $5d6s\!^{2} \; ^{2}\!D_{3/2} \rightarrow 5d6s6p \; ^{2}\!D_{3/2}$ were performed on all lutetium isotopes in the range of $^{161-179}$Lu. The nuclear spins, magnetic moments and quadrupole moments were determined from the hyperfine structures observed for 19 ground states and 11 isomers. Variations in the mean square charge radii as a function of neutron number were obtained from the isotope shifts. These data considerably extend the systematics of the properties of nuclei in the upper rare-earth region. A particular feature is the appearance of high-spin and low-spin ground states and isomeric states in the vicinity of the stable $^{175}$Lu, partly arising from aligned neutron pairs. The present results clearly show that the deformation properties are nearly independent of the occupancy and the coupling of single-particle states. Theoretical predictions of deformation are confirmed in a consistent description of the measured radii and quadrupole moments. For all observed states, the spins and magnetic moments allow the assignment of rather pure Nilsson configurations.