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Study of low-lying resonant states in 16F using an 15O radioactiveion beam

Description: A 120 MeV {sup 15}O radioactive ion beam with an intensity on target of 4.5 x 10{sup 4} pps has been developed at the 88-inch cyclotron at the Lawrence Berkeley National Laboratory. This beam has been used to study the level structure of {sup 16}F at low energies via the p({sup 15}O,p) reaction using the thick target inverse kinematics method on a polyethylene target. The experimental excitation function was analyzed using R-matrix calculations. Significantly improved values for the level widths of the four low-lying states in 16F are reported. Good agreement with the theoretical spectroscopic factors is also obtained.
Date: January 22, 2007
Creator: Lee, D.W.; Perajarvi, K.; Powell, J.; O'Neil, J.P.; Moltz, D.M.; Goldberg, V.Z. et al.
Partner: UNT Libraries Government Documents Department

Reinvestigation of the Direct Two-proton Decay of the Long-lived Isomer 94Agm [0.4 s, 6.7 MeV, (21+)]

Description: An attempt to confirm the reported direct one-proton and two-proton decays of the (21+) isomer at 6.7(5) MeV in 94Ag has been made. The 0.39(4) s half-life of the isomer permitted use of a helium-jet system to transport reaction products from the 40Ca + natNi reaction at 197 MeV to a low-background area; 24 gas Delta E-(Si) E detector telescopes were used to identify emitted protons down to 0.4 MeV. No evidence was obtained for two-proton radioactivity with a summed energy of 1.9(1) MeV and a branching ratio of 0.5(3)percent. Two groups of one-proton radioactivity from this isomer had also been reported; our data confirm the lower energy group at 0.79(3) MeV with its branching ratio of 1.9(5)percent.
Date: March 5, 2009
Creator: Cerny, J.; Moltz, D. M.; Lee, D. W.; Perajarvi, K.; Barquest, B. R.; Grossman, L. E. et al.
Partner: UNT Libraries Government Documents Department

The Structure of 12N using 11C + p resonance scattering

Description: The level structure of {sup 12}N has been investigated from 2.2 to 11.0 MeV in excitation energy using a {sup 11}C + p resonance interaction with thick targets and inverse kinematics. Excitation functions were fitted using an R-matrix approach. Sixteen levels in {sup 12}N were included in the analysis, several of them are new. Spin-parity assignments, excitation energies and widths are proposed for these levels. To fit the high energy part of the excitation function, imaginary phase shifts had to be added to the phase shifts generated by the hard sphere scattering.
Date: March 2, 2006
Creator: Perajarvi, K.; Chang, Bo Fu; Rogachev, G.V.; Chubarian, G.; Goldberg, V.Z.; Guo, Q. et al.
Partner: UNT Libraries Government Documents Department

Production of beams of neutron-rich nuclei between Ca and Ni using the ion-guide technique

Description: Since several elements between Z = 20-28 are refractory in their nature, their neutron-rich isotopes are rarely available as low energy Radioactive Ion Beams (RIB) in ordinary Isotope Separator On-Line facilities [1-4]. These low energy RIBs would be especially interesting to have available under conditions which allow high-resolution beta-decay spectroscopy, ion-trapping and laser-spectroscopy. As an example, availability of these beams would open a way for research which could produce interesting and important data on neutron-rich nuclei around the doubly magic {sup 78}Ni. One way to overcome the intrinsic difficulty of producing these beams is to rely on the chemically unselective Ion Guide Isotope Separator On-Line (IGISOL) technique [5]. Quasi- and deep-inelastic reactions, such as {sup 197}Au({sup 65}Cu,X)Y, could be used to produce these nuclei in existing IGISOL facilities, but before they can be successfully incorporated into the IGISOL concept their kinematics must be well understood. Therefore the reaction kinematics part of this study was first performed at the Lawrence Berkeley National Laboratory using its 88'' cyclotron and, based on those results, a specialized target chamber was built[6]. The target chamber shown in Fig. 1 was recently tested on-line at the Jyvaaskylaa IGISOL facility. Yields of mass-separated radioactive projectile-like species such as {sup 62,63}Co are about 0.8 ions/s/pnA, corresponding to about 0.06 % of the total IGISOL efficiency for the products that hit the Ni-degrader. (The current maximum 443 MeV {sup 65}Cu beam intensity at Jyvaaskylaa is about 20 pnA.) This total IGISOL efficiency is a product of two coupled loss factors, namely inadequate thermalization and the intrinsic IGISOL efficiency. In our now tested chamber, about 9 % of the Co recoils are thermalized in the owing He gas (p{sub He}=300 mbar) and about 0.7 % of them are converted into the mass-separated ion beams. In the future, both of these ...
Date: September 28, 2004
Creator: Perajarvi, K.; Cerny, J.; Hager, U.; Hakala, J.; Huikari, J.; Jokinen, A. et al.
Partner: UNT Libraries Government Documents Department