capture touching point M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March

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1 Nuclear Reaction Mechanism Induced by Heavy Ions MG M.G. Itkis Joint Institute for Nuclear Research, Dubna 5 th ASCR International Workshop Perspectives in Nuclear fission Tokai, Japan, March 212

2 capture Compound nucleus n n ER n n touching point Quasielastic& Deepinelastic Quasifission CN fission M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March 212 2

3 Double arm time-of-flight flight spectrometer CORSET Basic Characteristic of the spectrometer CORSET for binary reaction fragments (double ToF): Time Resolution 15ps Mass resolution ~2 a.m.u. amu Solid angle of each arm 15 mstr Range of the measured angles: In the reaction plane From 2 to 16 ±3 Out of plane ±1 Neutron spectrometer 8-5 neutron detectors DEMON -rays spectrometer M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March NaI(Tl) or BaF2 detectors 3

4 Heavy ion induced induced reactions: binary channel 64 Ni+ 186 W 25 No * E * 4 MeV (MeV) TKE ~1 2 s QFsym+CNF ~1 21 s QFasym < m < 125 (x1) Counts Mass (u) d /d d (mb/rad d) < m < c.m. (deg) M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March 212 4

5 Presence of Qf in the medium composite systems (A~19 23u) 12 C + 24 Pb 216 Ra 48 Ca Er 216 Ra <TKE > (MeV) Yield TKE (MeV) E lab = 73 MeV E * = 4.5 MeV E lab = 194 MeV E * = 4.4 MeV Z=28 Z=5 N=82 N= d /d d c.m. (arb.u.) 48 Ca+ 168 Er 216 Ra E * =41 MeV u (x1) u c.m. (deg) Mass, u Mass (u) M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March 212 5

6 Mass energy distributions for the 48 Ca+ 144,154 Sm at energies near the Coulomb barrier Ca+ 154 Sm 22 Pb * 48 Ca+ 144 Sm 192 Pb * E lab =182 MeV lab E lab =19 MeV Counts TKE, MeV <TKE>, MeV N=5 N=82 Z=5 15 Z=28 4 Z=5 Z=28 1 N=82 5 N= mass, amu mass,amu

7 Competition between fusion and QF processes: Hs (Z=18) composite systems 22 Ne Cf 271 Hs 26 Mg Cm 274 Hs 36 S U 274 Hs 58 Fe + 28 Pb 266 Hs 3 E * = 52 MeV E * = 64 MeV CN CN E * = 56 MeV E * =48 MeV CN CN 25 TKE (M MeV) 15 3 E * = 29 MeV CN * * E CN = 35 MeV E * =35 MeV E CN CN =33 MeV Mass (u) Z 1 Z 2 = I. M. Itkis et al., Phys. Rev. C 83 (211) M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March 212 7

8 TKE distributions of symmetric fragments units) Yield (relative E CN = 29 MeV E * 22 Ne Cf <TKE> = 214 ± 2 MeV TKE = 23.5 MeV <TKE> = 215 ± 1 MeV.2 TKE = 21.5 MeV.2 = 52 MeV E * CN E * 26 Mg Cm E CN =35 MeV <TKE> = 218 ± 1 MeV TKE = 22.6 MeV <TKE> = 215 ± 1 MeV TKE = 22.5 MeV E * = 64 MeV CN S U S <TKE> = 21 ± 2 MeV TKE = 14.6 MeV E * = 35 MeV CN <TKE> = 213±1 MeV TKE = 21.6 MeV.2 E * = 4 MeV CN Fe + 28 Pb <TKE> = 211 ± 1 MeV E * TKE = 18 MeV = 21 MeV CN E * = 41 MeV CN <TKE> = 218 ± 1 MeV TKE = 2 MeV TKE <TKE> = 214 ± 1 MeV TKE = 24.4MeV.2 E * = 56 MeV.2 CN E * = 48 MeV CN <TKE> = 22 ± 1 MeV TKE = 2 MeV TKE (MeV) TKE (MeV) TKE (MeV) M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March TKE (MeV) 8

9 Fusion probability P CN for the reactions with 26 Mg and 36 S ions The properties of entrance channels strongly affect the reaction dynamics. At the excitation energy near the barrier the estimated values of P CN are ~7% in the case of the Mg induced reaction and ~25% in the S induced reaction. P CN Mg Cm 36 S+ 238 U M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March 212 E c.m. -E Bass (MeV) 9

10 Yi eld (relati ive units).25 E CN =35 MeV E * 26 Mg Cm TKE (MeV) counts Yields, Bimodal fission 258 Fm sf 259 Md sf Md 15 sf No sf No 1 sf Mass (u) Mass (u) M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March TKE (MeV) 1

11 M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March

12 Superasymmetric fission of superheavy nuclei WG W. Greiner (International ti Workshop on Fusion Dynamics at the Extremes, 25-27May ) Superasymmetric fission of nuclei with A~ u 12 M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March 212

13 Proposed experiment: Supeasymmetric fission of No nucleus ( 48 Ca/ 28 Pb) 48 Ca+ 28 Pb 256 No TKE [MeV] C ounts Z 28 E * =42 MeV N 5 The reaction 12 C+ 248 Cm 26 No 48 Ca+ 28 Pb+4n Energy close to the Coulomb barrier the excitation of the CN is about 35 4MeV when the shell effects still exist; The contribution of QF process in this reaction is negligible due to the small value of Z 1 Z 2 =576 QF / cap 2% M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March

14 Reactions with 48Ca ions * E CN = 18 MeV TKE (MeV) Yield (relative units) TK KE (MeV) 48 Ca U (E * 48 Ca U =35MeV) CN 26 MeV 35 MeV 45 MeV Z=5 N= Yield (%) MeV Mass (u) Mass (a.m.u.) 4 2 M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March

15 Asymmetric QF in the syperheavy composite systems 36 S+ 238 U 274 Hs * 48 Ca+ 238 U 286 Cn * 64 Ni+ 238 U * 35 E*=46 MeV E*=35 MeV E*=31 MeV Yields (arb.u.) TKE (MeV) M= u M=28 u M=215 u Mass (u) M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March

16 The widths of Qfasym mass distributions FW WHM QFasy ym (MeV) Ca+ 238 U 48 Ca+ 248 Cm 36 S+ 238 U,92,94,96,98 1, 1,2 1,4 1,6 1,8 Dri iving potent tial (MeV) Ca+ 248 Cm 2u 48 Ca+ 238 U 15u 23u 36 S+ 238 U E c.m /E Bass Mass (u) While therelative lti contribution tibti of QF to the capture cross section mainly depends on the reaction entrance channel properties, the features of asymmetric QF are determined essentially by the driving potential of composite system. M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March

17 Normal Asymmetric QF Reverse Ca Cm U Cm Yie ld (arb. unit) QF QF+CNF X potemtial (M MeV) Driving Z Z=28 Mass (u) N=5 N=126 Z=5 N=82 Z= N=126 Mass (u) Z=82 Driving potential is calculated near the scission point in nrv.jinr.ru (proximity model) M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March

18 Asymmetric QF Reverse Xe Cm U Cm potential (M MeV) Driving N= nrv.jinr.ru (proximity model) Mass (u) Z=114 N= Z N=126 Mass (u) Z=82 M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March

19 136Xe+248Cm 6 5 potential en nergy (MeV) 4? Z= nrv.jinr.ru (proximity model) elongation (fm) mass asymmetry M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March

20 136 Xe+ 248 Cm???? 238 U+ 248 Cm M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March 212 2

21 Transition from Ca to Ni: Mass energy distribution for 25 No Ca+ 26 Pb 25 No 64 Ni+ 186 W 25 No E * 3 MeV E * 4 MeV E * 3 MeV E * 4 MeV 25 TKE, MeV 15 Yield, counts <T TKE>, MeV Z=28 N=5 N=82 N= N=82 1 N=5 N=88 N=5 N= N=88 8 N=82 N=82 6 N= Z= Mass, amu 21

22 Mass angle angle distributions of thereaction fragments at E * 4 MeV 22 G. N. Knyazheva et al., Phys. Part. and Nuclei Lett. 5, 21 (8) 1 Reaction counts Ca(227 ( MeV)+ ) 26 Pb 25 No N=82 <A> N=88 <TKE> К amu MeV ħ deg Ni(311 MeV)+ ) 186 W 25 No 1-21 с N=5 4 Z= Ca + 26 Pb , 231 ~4, counts , , Ni W , 226 ~ 4, mass, u mass, u ) 2 44 Ca(227 MeV) Pb 25 No 16, Ni(311 MeV)+ 186 W 25 3,2 No 1 15 < m < 125 (x1) < m < 125 (x1) d /d, mb/ra ad < m < 85 rad d /d, mb/r < m < c.m., deg c.m., deg 22

23 E * CN 45Me V 48 Ca+ 238 U 286 Cn Viola Systematics Z t Z p Y(A 3 2. CN /2±2)=12 7 % 6 7% u Fe+ Pu Y(A CN /2±2)=8% % TKE (MeV) 1 Yield (a arb. units) Ni+ U u Y(A CN /2±2)=4% 11 u Cou unts % Mass (u) Mass (u) TKE (MeV) for A CN /2±2

24 Cross section for the 64Ni+238U reaction The capture cross section is about a few hundred millibarns at energy above the Coulomb barrier (about 4 5 times less than for the reaction 48Ca+238U). 64 Ni+ 238 U The formation cross section of fragments with masses A -1 CN /2±2 u is one order of 1 magnitude less compare with Ca induced 1 reactions. -2 The estimated value of formation probability of compound nucleus formed in the reaction 64Ni+238U drops three orders of magnitude with respect to the 48Ca+238U reaction. This is unfortunately a limiting factor. Thus, we conclude that the reaction 64Ni+238U is not suitable for the synthesis of the synthesis of element Z=12. PLB 686 (21) 227 (m mb) (pb) M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March 212 B Bass capture A /2±2 CN (A CN /2±2)&TKE capture Toke et al Hofman et al E c.m. (MeV) 24

25 1 2 No Ds 114 Cn CNF / cap (%) 1 48 Ca 58 Fe Ni ER cross sectio on (pb) No Neutron number Rf Db P CN = CN / cap Sg CN Bh CNF xn =W Rf sur P CN cap Ne (4n) Mg (4n) S (5n) Ca (4n) Fe Ds Cn Ni Neutron number M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March

26 Conclusion While the relative contribution of QF to the capture cross section mainly depends on the reaction entrance channel properties, the features of asymmetric QF are determined essentially by the driving potential of a composite system. The fragment yield increases when the both formed fragments are close to nuclear shells as in the case of QF (asymmetric QF), as well as in the case of fusion fission (bimodal fission, asymmetric fission, superasymmetric fission). At the transition from Ca to Ni projectiles the contribution of QF process rises sharply and Ni ions is not suitable for the synthesis of element tz=12 in the complete lt fusion reactions. An alternative way for further progress in SHE can be achieved using the deep inelastic or QF reactions. To estimate the formation probabilities of SHE in these reactions the additional investigations are needed. M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March

27 Collaboration I.M. Itkis, M.G. Itkis, G.N.Knyazheva, E.M. Kozulin Flerov Laboratory of Nuclear Reactions, JINR, Dubna, Russia F.Goennenwein Physikalisches Institut, Universität Tübingen, 7276 Germany E. Vardaci INFN and Dipartamento di Scienze Fisiche dell Universita di Napoli, Napoli, Italy F. Hanappe Universite Libre de Bruxelles, Bruxelles, Belgium O. Dorvaux, L. Stuttge Institut Pluridisciplinaire Hubert Curien, Strasbourg, France W. Trzaska Department of Physics, University of Jyväskylä, Finland Thank you for your attention! M.G. Itkis, Perspectives in Nuclear fission Tokai, Japan, March

28 Reactions with 28 Pb target TK KE, MeV Ca + 28 Pb 256 No ( E * = 33 MeV) 5 Ti + 28 Pb 258 Rf ( E * = 29 MeV) N=5 Z=28 58 Fe + 28 Pb 266 Hs ( E * = 32,3 MeV) 86 Kr + 28 Pb ( E * = 26 MeV) mass, u Coun nts