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J.H. Hamilton 1, S. Hofmann 2, and Y.T. Oganessian 3 1 Vanderbilt University, 2 GSI 3 Joint Institute for Nuclear Research ISCHIA 2014
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102
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(a)Calculated ground-state shell-correction energy, (b)partial spontaneous fission (SF), and (c)α-particle half-lives (Smolanczuk, Sobiczewski).
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102 184
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X 117
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cold hot
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Velocity separator SHIP SHIP: Separation time: 1 – 2 μs Transmission: 20 – 50 % Back ground: 10 – 50 Hz Energy resolution: 18 – 25 keV Position resolution 150 μm Dead time: 3 – 25 μs
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The Dubna gas-filled recoil separator DGFRS and detectors are shown.
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20 9420 96 92
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292 116 CN 288 114 284 Cn 2.75 MeV (escape) 3.3 ms 9.959 MeV 993 ms 172 MeV, uncorrected 50 ms 11 22 sf 02-July-2010, 01:52 h; chain 2 8.96 MeV, 10.4 mm, strip 4 292 116 CN 288 114 284 Cn 10.624 MeV 76 s 9.895 MeV 1.3 s 197 MeV, uncorrected 269 ms 11 22 sf 03-July-2010, 20:01 h; chain 3 18 MeV, 27.4 mm, strip 2 292 116 CN 288 114 284 Cn 1.4 MeV (escape) 28.8 ms 1.8 MeV (escape) 252 ms 195 MeV, uncorrected 121 ms 11 22 sf 07-July-2010, 00:10 h chain 4 22 MeV, 24 mm, strip 15 292 116 CN 288 114 284 Cn ≈10.6 MeV (stop + box) 11.6 ms ≈10.0 MeV (stop + box) 72 ms 185 MeV, uncorrected 25 ms 11 22 sf 07-July-2010, 09:01 chain 5 21.0 MeV, 28 mm, strip 12 Experiment SHIP, June 24 – July 26, 2010 48 Ca + 248 Cm => 292 116 + 4n
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black - experiment, blue – theory Note the good agreement of the macroscopic- microscopic calculated alpha energies (blue) and our experimental ones (black). 70 days run Note decay not SF as for 281 Rg
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Definitive evidence for elements 113, 115 in the reaction 243 Am + 48 Ca Two sets of experiments from November 2010 – February 2012. Five different beam energies were used.
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2728 2 3 4 Since PRL 2012
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Cross bombardment check
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New 249 Bk target for Dubna and GSI 2012, 2013 Dubna 48 Ca + 249 Bk 11 new events of 293 117 and 3 new events of 294 117. Totals 16 events of 293 117 and 4 of 294 117. One new 48 Ca + 249 Cf 294 118 + 3n GSI 48 Ca + 249 Bk Confirmed 294 117. 50 Ti + 249 Bk 296 119 + 3n No events seen; less than 70 femtob after 6 months.
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D. Rudolph, Lund University APSORC 13, Kanazawa, Japan, September 2013 Alpha-Gamma Spectroscopy on 288 115 22 chains (out of 30) of ours are compatible with the 31 chains (out of 37) associated with the 3n channel 288 115 by Oganessian et al. 8.73-9.15 12.0( ) 288 115 284 113 280 Rg 276 Mt 272 Bh 268 Db 9.17-9.95 0.54( )/6( ) 9.09-9.87 3.6( ) 9.97(5),9.81(7) 0.97( ) 10.33-10.58 0.171( ) 27( ) h DGFRS 42 28 25 17 9696 8282 14 9 31 21 5454 8.55-9.09 9.2( ) 288 115 284 113 280 Rg 276 Mt 272 Bh 268 Db 9.43-9.89 0.75( ) 9.25-9.92 6.4( ) 9.10-10.11 0.81( ) 10.29-10.56 0.150( ) 26( ) h (and γ rays!) TASCA 43 28 23 15 21 13 25 15 31 18 7575 D. Rudolph et al., PRL 111 (2013) 112502 s s s s s
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Partial half-lives for SF vs. N. solid symbols and crosses denote even-even, open symbols – even-odd nuclei. Solid lines are drawn through the experimental points of even-even nuclei. The dashed lines are calculated T SF (th).
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Radioactive properties: (a) -particle energies Q for odd-Z nuclei agree with the systematics and have intermediate values between neighboring even-Z nuclei. (b) -particle energies of the Z=107 and Z=109 isotopes as well as their behavior vs neutron number are in agreement with what is observed for the neighboring lighter previously known nuclei. (c) Decrease of Q values with approaching N=184 magic number -- increase of stability.
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Radioactive properties: increase of stability with approaching N=184 magic number
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281 111(N=170) lies in the “critical” region between the stabilizing effect of the N=162 and 184 neutron shells.
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The high hindrance caused by the odd proton does not save 281 111(N=170) from SF because of the weakening of the above neutron shells. 282 111(N=171) has an extra unpaired neutron that further hinders SF relative to alpha decay. Thus this nucleus undergoes alpha decay.
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less than 70 femtob after 6 months at TASCA.
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Warmest best wishes for health and long life to Prof. Aldo Covello
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