Viola and the Heavy Elements

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Viola and the Heavy Elements

• W. Loveland
• Oregon State University

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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

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Vics Nucleus--The Union Card

• Grad student in the Seaborg group
• Numerous important contributions
• 226U

Current data t1/20.35 s, E?7.57 MeV
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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).
  (Z50-118, A130-311)
• 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)

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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
Viola Systematics-1966
Viola systematics-1985
Simple fit to the data
Pocket formula
Note limits on range of applicability
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Physics Issues
r0 1.8 ?2R D
D ? Initial Kinetic Energy of Fragments
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New Developments
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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).
pfrag
pCN/2

• Diagnostic for the occurrence of incomplete
  fusion
• A tool to study the mechanism of intermediate
  energy
• colliisions

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Transfer Product Yields
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Heavy Element Synthesis
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Search for Element 112 in the 238U(48Ca,3n)
Reaction

• Y.T. Oganessian et al. reported (Eur. J. Phys A5,
  63 (1999))
• 231 MeV 48Ca 238U ? 286112 ? 283112 ? SF
• Two events were observed (t½ 81 (147, -32) s)
• Dose 3.5 x 1018, ? 5.0 (6.3, -3.2) pb
• Somewhat unexpected decay mode

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What is so special about 283112 and its synthesis?

• 283112 occurs in the decay of 291116 formed in
  the 245Cm 48Ca reaction.
• 283112 occurs in the decay of 287114 formed in
  the 244Pu 48Ca reaction.
• 283112 should be the most easily reachable hot
  fusion product.

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Chronology of Studies of 238U(48Ca,3n) 283112
Reaction

• 1999--Vassilissa group reports synthesis of
  283112 with ? 5 pb, t1/2 3 m, decay SF,
  Elab231 MeV
• 2002--BGS group fails to find 283112, ?upper 0.9
  pb, 0ltt1/2lt1000s, decay ?,SF, Ebeam 231 MeV
• 2004--Vassilissa group fails to find 283112 at
  Ebeam 231 MeV, ?upper 2.2 pb.
• 2004--Vassilissa group finds 283112 at Ebeam
  234 MeV, ? 4 pb, t1/2 5.1 m, decay SF
• 2004--DGFRS group fails to find 5 min SF
  activity, says 283112 is an ?-emitter with t1/2
  6 s (produces this nucleus directly and in decay
  of 291116 and 287114.)
• 2004--BGS group tries again to make 283112 at
  Ebeam 236 MeV without success.
• 2005--Swiss group fails to confirm DGFRS or
  Vassilisa results
• 2005--GSI group fails to confirm DGFRS or
  VASSILISSA results but finds one event (t7 s,
  decay SF, ?0.5 pb)--disagrees with everyone.

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Summary of BGS Experiments
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RESULTS

• NO SF events in any irradiation
• No EVR-?-? correlations ( T lt 20 s) in any
  irradiation.

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Summary of Experiments

• Vassilissa group 283112 is SF nucleus, with t1/2
  5 min, ? 4 pb
• DGFRS group 283112 is ? emitter (SF lt 10), t1/2
  6 s, ? 2.5 pb
• GSI group 283112 is SF nucleus, t1/2 5 s, ?
  0.7 pb
• BGS group 283112 not found, ?upper 0.9 pb

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Thanks, Vic