V. Sebastian

The ISOLDE laser ion source for exotic nuclei

At the ISOLDE on line mass separator a system of copper vapor lasers and dye lasers serves for resonant ionization of atoms inside a hot cavity attached to the target. Radioactive ion beams of Yb, Ag, Mn, Ni, Zn, Be, Cu, Cd and Sn were produced with the Resonance Ionization Laser Ion Source (RILIS). Two and three step excitation schemes are used, providing an ionization efficiency of about 10%. Thanks to the use of the RILIS it became possible to ionize beryllium efficiently at ISOLDE, and all particle stable Be isotopes could be separated for the first time. Separation of Ag and Cu nuclear isomers was achieved in the ion source by appropriate tuning of the laser wavelength. New isotopes of Ag, Mn, Zn, Cd and Sn were found, including the r process “waiting point” nucleus 129Ag.

Recent developments of the ISOLDE laser ion source

The ISOLDE laser ion source (LIS), in which stepwise resonant laser ionization is performed inside a high-temperature cavity, has been extended to include the elements Be, Zn, Cu and Cd. The ionization efficiencies obtained are discussed with respect to the level of saturation of each step achieved with the available laser beam intensities. Because of a high ionization potential of about 9 eV the first resonant transition of Be, Zn and Cd is in the far ultraviolet (UV) region. The UV laser beam needed for the first resonant step of Be, Zn and Cd is achieved in a new laser setup via frequency tripling of the dye laser light. The ions created during the 30 ns laser pulse are extracted from the hot cavity of the ion source by the electrical field resulting from the ohmic heating of the cavity. The time distribution of the laser-ionized ion bunches was measured for various cavities and temperatures. The time structure of the ion bunch is discussed in order to gain insight into the development of LIS cavities.

A new measurement of the 7Be(p,γ)8B cross-section with an implanted 7Be target

Abstract The 7 Be(p, γ ) 8 B capture reaction is of major importance to the physics of the sun and the issues of the “solar neutrino puzzle”. We report here on a new determination of the absolute cross section of this reaction, using a novel method which overcomes some of the major experimental uncertainties of previous measurements. We utilize a 7 Be target implanted into a Cu substrate and a uniformly scanned particle beam larger than the target spot, eliminating issues of target homogeneity and backscattering loss of 8 B reaction products. The target was produced using a beam of 1.8·10 10 /s 7 Be nuclei extracted at ISOLDE (CERN) from a graphite target bombarded by 1 GeV protons in a two-step resonant laser ionization source. The 7 Be nuclei were directly implanted into a copper substrate to obtain a target of 2 mm diameter with a total of 3.10 15 atoms. The measurement of the 8 B production cross section was carried out at the Van de Graaff laboratory of the Weizmann Institute of Science. We obtain for the S factor of the reaction: S 17 ( E cm = 1.09 MeV) = 22.7(1.2) eV. barn and S 17 ( E cm = 1.29 MeV) = 23.8(1.5) eV. barn, somewhat higher than other recent measurements. The present results can serve as a benchmark for further measurements of this cross section.

COMPLIS experiments: COllaboration for spectroscopy Measurements using a Pulsed Laser Ion Source

Laser spectroscopy measurements have been carried out on very neutron-deficient isotopes of Au, Pt and Ir, produced as daughter elements from a Hg ISOLDE beam. For these transitional region nuclides, the hyperfine structure (HFS) and isotope shift (IS) were measured by Resonance Ionization Spectroscopy (RIS). Magnetic moments μ, spectroscopic quadrupole moments Qs and changes of the nuclear mean square charge radius δ〈rc2〉along isotopic series have been extracted. For some results, a detailed comparison with theoretical predictions is presented.

Laser ionization in β decay studies of Zn and Mn nuclei

Resonance ionization laser ion source (RILIS) technique has been used in the β-decay studies of 59Mn and 58Zn. The importance of the RILIS for production of these elements is discussed. The properties of the low-lying levels of the studied nuclei are discussed.

Nuclear moments of neutron deficient iridium isotopes from laser spectroscopy

AbstractLaser spectroscopy measurements have been performed on neutron deficient iridium isotopes. The hyperfine structure and isotope shift of the optical Ir I transition 5d76s24F9/2 → 5d76s6p 6F11/2 at 351.5 nm have been studied for the 182–189Ir, n

Test of special relativity in an ion storage ring

^{186} {text{Ir}}^user1{m}

Measurement of the 7Be(p,γ)8B cross-section with an implanted 7Be target

n and 191,193Ir isotopes. The nuclear magnetic and quadrupole moments were obtained from the HFS measurements and the changes of the mean square charge radii from the IS measurements. A large mean square charge radius change between 187Ir and 186Ir and between n