1. Katsuhisa Nishio Advanced Science Research Center Japan Atomic Energy Agency Tokai, JAPAN ARIS2014 Tokyo Mass Asymmetric Fission of Iridium Nucleus Mass Asymmetric Fission of Nucleus Produced in 7 Li + 186 W

2. ① K. Nishio, K. Hirose, I. Nishinaka, H. Makii, R. Orlandi, R. Léguillon, J. Smallcombe, S. Mitsuoka, T. Ishii, H. Ikezoe ② A. Andreyev ③ N. Tamura, S. Goto ④ T. Ohtsuki ⑤ I.Tsekhanovich ⑥ P. Möller ① ② ③ ④ ⑤ ⑥

3. - particle induced x - e.m. –induced E*~11 MeV 187 Ir 196 Au Z=82 180 Hg N/Z=1.25 Region of our interest I: beta- delayed fission of A~180-200 N/Z~1.22-1.3: Tl,Bi, At, Fr ISOLDE(CERN) Properties for Low-Energy Fission A. Andreyev et al., Phys. Rev. Lett.105, 252502 (2010).

4. Calculated Fission Fragment Yield 180 Hg Calculated by P. M ö ller (LANL) and J. Randrup (LBNL) P. Möller, 10 th ASRC International Workshop, “ Nuclear Fission and Structure of Exotic Nuclei ”, 2013.March, Tokai, Japan 193 Ir 7 Li + 186 W  193 Ir*

5. JAEA at Tokai and Tandem Facility 20 MV Tandem accelerator (20UR) Tokai Campus, JAEA Tokyo Tandem facility J-PARC

6. Time difference signal of FFs in 7 Li + 186 W 186 W MWPC2 MWPC1 Fragment 2 Fragment 1 7 Li Beam Time difference (ch) Counts E c.m. = 65.5MeV 40.0 MeV 30.0 MeV 44 o

7. Fragment Mass Distributions in 7 Li + 186 W 31.1 MeV 68.0 MeV 41.5 MeV E lab Fragment Mass (u) 110 Ru 83 As Events (u) Fusion reaction is assumed 7 Li + 186 W  193 Ir* N = 50 N = 66

8. Folding Angle between Fission Fragments θ fold = θ 1 + θ 2 (deg) Complete Fusion 7 Li + 186 W θ fold =169 o E lab = 31.1 MeV Beam FF 1FF 2 θ1θ1 Recoiled Fissioning Nucleus θ2θ2 Counts

9. Analysis assuming fusion-fission Viola Formula from Phys. Rev. C 31, 1550 (1985) 7 Li + 192 Os  199 Au* Fragment Mass (u) TKE (MeV) Folding Angle (deg.) =134 MeV θ fold, =167.9 o TKE (MeV) 7 Li + 186 W  193 Ir* θ fold =167.5 o Fragment Mass (u) =129 MeV Folding Angle (deg.) E beam = 41.5 MeVZ=118

10. 7 Li + 186 W, 192 Os 31.1 MeV 41.5 MeV E Beam = 64.0 MeV  fold (deg)  (ns) -20 0 20 180 170 160 180 170 160 180 170 160 180 170 160 180 170 160 7 Li + 186 W 7 Li + 192 Os σ fiss = 67 μ b 110 μ b 14 μ b 2.1 μ b 0.8 μ b -20 0 20  (ns)

11. 192 Os 191 Os Break-up Fusion 187 Re 188 Re 189 Re 188 Os 189 Os 190 Os 185 W 186 Re 187 Os 189 Ir 190 Ir 191 Ir 188 Ir 192 Ir 193 Ir 184 W 185 Re 186 Os 187 Ir 186 W 186 W( 7 Li, α) 189 Re * 186 W( 7 Li, t) 190 Os* 189 Re 193 Ir p + 192 Os Counts Fragment Mass (u) 190 Os 7 Li  3 H + 4 He (Q= -2.467 MeV)

12. Break-up Fusion and Fission Fragment 1 Fragment 2 186 W 7 Li 4 He 3 H + 186 W  189 Re * 4 He 3H3H 4 He + 186 W  190 Os * 3H3H CNV Coul E beam,thres ( 7 Li) 4 He + 186 W 190 Os*20.3 MeV ̴ 36 MeV 3 H + 186 W 189 Re*10.3 MeV ̴ 24 MeV

13. Fission Barrier Height for 189 Re and 190 Os P. M ö ller, 16 th ASRC International Workshop, “ Nuclear Fission and Decay of Exotic Nuclei ”, 2014.March, Tokai, Japan 189 Re* or 190 Os* should have excitation energy larger than 25 MeV 189 Re, 190 Os Fission Barrier is 25 MeV

14.  (ns) Folding Angle at E* = 25 MeV of Fissioning Nucleus 7 Li + 186 W = 193 Ir* 31.1 MeV 41.5 MeV E lab E* max = 36 MeV 180 170 160 180 170 160 -20 0 20  fold (deg) 64.0 MeV 186 W( 7 Li, α ) 189 Re*, θ α = 45 o 186 W( 7 Li, t ) 190 Os*, θ t = 45 o 186 W( 7 Li, α ) 189 Re*, θ α = 55 o 186 W( 7 Li, α ) 189 Re*, θ α = 25 o 186 W( 7 Li, t ) 190 Os*, θt = 45 o 180 170 160

15. ΔE E Target 7 Li 186 W θ LAB ΔE-E t, α 7 Li Beam Setup for Break-up Fusion Induced Fission 189 Re*… MWPC1 MWPC2

16. Summary Mass-asymmetric fission was observed for nucleus produced in 7 Li + 186 W. The fissionig nucleus could be populated by break-up fusion. Coincidence experiment between particle and both fission fragments is planned.

18. Properties for Low-Energy Fission 180 Hg  A. Andreyev et al., Phys. Rev. Lett.105, 252502 (2010).

19.  (ns) Folding Angle Distribution at E* = 25MeV 186 W( 7 Li, α ) 189 Re*, θ α = 25 o, 173 186 W( 7 Li, α ) 189 Re*, θ α = 45 o, 172 186 W( 7 Li, α ) 189 Re*, θ α = 55 o, 172 186 W(7Li, t ) 190 Os*, θt = 45 o, 170.0 186 W( 7 Li, t ) 190 Os*, θ t = 45 o,170.0 o 186 W( 7 Li, t ) 190 Os*, θ t = 45 o, 170.0 7 Li + 186 W = 193 Ir* 31.1 MeV 41.5 MeV E lab E* max = 36 MeV E* max = 26 MeV 180 170 160 180 170 160 -20 0 20  fold (deg) 64.0 MeV 180 170 160

20. Summary

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24. Multi-nucleon Transfer Induced Fission 18 O + 232 Th E sum (MeV) Coincidence between particle and fission fragments O F N C B Be 15 N 232 Th( 18 O, 15 N) 235 Pa*  Transfer of 3 H

25. 232 Th( 18 O, 15 N) 235 Pa* → Fission Fragment Mass Distributions for 3 H Transfer Fragment mass yield (u) Excitation energy (MeV) Counts

26. 232 Th( 18 O, 18 O) 232 Th* Fragment Mass Distributions for 232 Th * 26 Fragment mass yield (u) Excitation energy (MeV)

27. Multi-nucleoon Transfer Induced Fission 18 O + 232 Th E sum (MeV) Coincidence between particle and fission fragments O F N C B Be

28. New Region for Mass Asymmetric Fission 80 100 A.Andreyev et al., Phys. Rev. Lett.105, 252502 (2010). 180 Hg 28 T. Ichikawa et al., Phys. Rev.C.86, 024610 (2012).

29. Theoretical Mass Yield 193 Ir 189 Ir

30. Fission Ｑ -value Fragment Mass (u) 2010 Q-value for Fission (MeV) Present 258 Fm 238 U 193 Ir 160 Gd Saddle Point Shape 1980 Large Fission Probability Small Fission Probability