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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(a)Calculated ground-state shell-correction energy, (b)partial spontaneous fission (SF), and (c)α-particle half-lives (Smolanczuk, Sobiczewski).
X 117
cold hot
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
The Dubna gas-filled recoil separator DGFRS and detectors are shown.
CN Cn 2.75 MeV (escape) 3.3 ms MeV 993 ms 172 MeV, uncorrected 50 ms 11 22 sf 02-July-2010, 01:52 h; chain MeV, 10.4 mm, strip CN Cn MeV 76 s 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 CN 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 CN 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 MeV, 28 mm, strip 12 Experiment SHIP, June 24 – July 26, Ca Cm => n
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
Definitive evidence for elements 113, 115 in the reaction 243 Am + 48 Ca Two sets of experiments from November 2010 – February Five different beam energies were used.
Since PRL 2012
Cross bombardment check
New 249 Bk target for Dubna and GSI 2012, 2013 Dubna 48 Ca Bk 11 new events of and 3 new events of Totals 16 events of and 4 of One new 48 Ca Cf n GSI 48 Ca Bk Confirmed Ti Bk n No events seen; less than 70 femtob after 6 months.
D. Rudolph, Lund University APSORC 13, Kanazawa, Japan, September 2013 Alpha-Gamma Spectroscopy on chains (out of 30) of ours are compatible with the 31 chains (out of 37) associated with the 3n channel by Oganessian et al ( ) Rg 276 Mt 272 Bh 268 Db ( )/6( ) ( ) 9.97(5),9.81(7) 0.97( ) ( ) 27( ) h DGFRS ( ) Rg 276 Mt 272 Bh 268 Db ( ) ( ) ( ) ( ) 26( ) h (and γ rays!) TASCA D. Rudolph et al., PRL 111 (2013) s s s s s
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).
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.
Radioactive properties: increase of stability with approaching N=184 magic number
(N=170) lies in the “critical” region between the stabilizing effect of the N=162 and 184 neutron shells.
The high hindrance caused by the odd proton does not save (N=170) from SF because of the weakening of the above neutron shells (N=171) has an extra unpaired neutron that further hinders SF relative to alpha decay. Thus this nucleus undergoes alpha decay.
less than 70 femtob after 6 months at TASCA.
Warmest best wishes for health and long life to Prof. Aldo Covello