Abstract. A gas-filled segmented linear Paul trap has been installed at the focal plane of the high-resolution separator (HRS) at CERN-ISOLDE. As well as providing beams with a reduced transverse emittance, this device is also able to accumulate the ions and release the sample in bunches with a well-defined time structure. This has recently permitted collinear laser spectroscopy with stable and radioactive bunched beams to be demonstrated at ISOLDE. Surface-ionized 39,44,46 K and 85 Rb beams were accelerated to 30 keV, mass separated and injected into the trap for subsequent extraction and delivery to the laser setup. The ions were neutralized in a charge exchange cell and excited with a co-propagating laser. The small ion beam emittance allowed focussing in the ion-laser overlap region, which is essential to achieve the best experimental sensitivity. Fluorescent photons were detected by a photomultiplier tube as a frequency scan was taken. A gate (typically 7-12 μs wide) was set on the photomultiplier signal to accept the fluorescent photons within the time window defined by the bunch. Thus, using accumulation times of 100 ms, the dominant contribution to background due to continuous laser scattering could be reduced by a factor of up to 4 × 10 4 .

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Refractory elements, i.e. elements with very high melting point and low vapor pressure, cannot be released in atomic form from an ISOL target. Therefore most of these elements are presently not available as ISOL beams. However, when reactive gases are introduced into the target, they may form volatile compounds with the refractory elements, allowing for an easier transport to the ion source. Particularly useful are high-temperature stable fluorides and oxides. By these chemical evaporation methods so far ISOL beams of the refractory elements C, Zr, Hf and Ta have been produced. We discuss how ISOL beams of B, Ti, Nb, Mo, Tc, Ru, W, Re, Os and Ir could be produced in a similar way. PACS. 28.60.+s Isotope separation -29.25.Ni Ion sources -29.25.Rm Sources of radioactive nuclei -82.40.-g Chemical kinetics and reactions: special regimes and techniques This work was supported by the EU-RTD project TAR-GISOL (contract HPRI-CT-2001-50033).1 This is valid when the type of atom-surface bonds is similar to that in solid state and the same monomolecular species dominate desorption and sublimation.