Slide 1

Viola and the Heavy Elements W. Loveland Oregon State University Slide 2 Vics Contributions to the Heavy Element Field Vics Nucleus Systematics of the properties of the heaviest elements TKE release in fission Linear Momentum Transfer Transfer Product Yields Slide 3 Vics Nucleus--The Union Card Grad student in the Seaborg group Numerous important contributions 226 U Current data t 1/2 =0.35 s, E =7.57 MeV Slide 4 Systematics of the properties of the heaviest elements Masses, Q , Q V.E. Viola, Jr. and G.T. Seaborg, J. Inorg Nucl.Chem. 28, 697 (1966). V.E. Viola, Jr., J. A. Swant, and J. Graber, At. Data and Nucl Data Tables 13, 35 (1974). (Z=50-118, A=130-311) Lifetimes V.E. Viola, Jr. and G.T. Seaborg, J. Inorg. Nucl Chem. 28, 741 (1966) V.E. Viola, Jr. and B.D. Wilkins, Nucl. Phys. 82, 65 (1966) Slide 5 Slide 6 Slide 7 Slide 8 TKE Release in Fission V.E. Viola, Jr. Nucl. Data A1, 391 (1966) V.E. Viola, K. Kwiatkowski, and M. Walker, Phys. Rev. C 31 1550 (1985). Simple-Minded Approach Simple fit to the data Pocket formula Viola Systematics-1966 Viola systematics-1985 Note limits on range of applicability Slide 9 Slide 10 Physics Issues r 0 ~ 1.8 2R + D D Initial Kinetic Energy of Fragments Slide 11 Slide 12 New Developments Slide 13 Linear Momentum Transfer T. Sikkeland, E.L. Haines, and V.E. Viola, Jr., Phys. Rev 125, 1350 (1962) V,E. Viola, et al., Phys, Rev. C 26,178 (1982). p frag p CN /2 Diagnostic for the occurrence of incomplete fusion A tool to study the mechanism of intermediate energy colliisions Slide 14 Slide 15 Slide 16 Transfer Product Yields Slide 17 Heavy Element Synthesis Slide 18 Search for Element 112 in the 238 U( 48 Ca,3n) Reaction Y.T. Oganessian et al. reported (Eur. J. Phys A5, 63 (1999)) 231 MeV 48 Ca + 238 U 286 112 283 112 SF Two events were observed (t = 81 (+147, -32) s) Dose = 3.5 x 10 18, = 5.0 (+6.3, - 3.2) pb Somewhat unexpected decay mode Slide 19 What is so special about 283 112 and its synthesis? 283 112 occurs in the decay of 291 116 formed in the 245 Cm + 48 Ca reaction. 283 112 occurs in the decay of 287 114 formed in the 244 Pu + 48 Ca reaction. 283 112 should be the most easily reachable hot fusion product. Slide 20 Chronology of Studies of 238 U( 48 Ca,3n) 283 112 Reaction 1999--Vassilissa group reports synthesis of 283 112 with ~ 5 pb, t 1/2 ~ 3 m, decay =SF, E lab =231 MeV 2002--BGS group fails to find 283 112, upper ~ 0.9 pb, 0 Slide 21 Summary of BGS Experiments Slide 22 RESULTS NO SF events in any irradiation No EVR- - correlations ( T < 20 s) in any irradiation. Slide 23 Slide 24 Summary of Experiments Vassilissa group 283 112 is SF nucleus, with t 1/2 ~ 5 min, ~ 4 pb DGFRS group 283 112 is emitter (SF < 10%), t 1/2 = 6 s, ~ 2.5 pb GSI group 283 112 is SF nucleus, t 1/2 ~ 5 s, ~ 0.7 pb BGS group 283 112 not found, upper ~ 0.9 pb Slide 25 Slide 26 Thanks, Vic