Investigating nuclear dissipation properties at large deformations via excitation energy at scission
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摘要
Using the stochastic Langevin model coupled with a statistical decay model,we study nuclear dissipation properties at large deformations with excitation energy at scission(E*_(sc)) measured in experiments.It is found that the postsaddle dissipation strength required to fit E*_(sc) data is 12*10~(21) s~(-1)for~(254;256)Fm and 6*10~(21) s~(-1)for~(189)Au,which has a smaller postsaddle deformation than the former heavy nucleus,showing a rise of nuclear dissipation strength with increasing deformation.
Using the stochastic Langevin model coupled with a statistical decay model,we study nuclear dissipation properties at large deformations with excitation energy at scission(E*_(sc)) measured in experiments.It is found that the postsaddle dissipation strength required to fit E*_(sc) data is 12*10~(21) s~(-1)for~(254;256)Fm and 6*10~(21) s~(-1)for~(189)Au,which has a smaller postsaddle deformation than the former heavy nucleus,showing a rise of nuclear dissipation strength with increasing deformation.
Using the stochastic Langevin model coupled with a statistical decay model,we study nuclear dissipation properties at large deformations with excitation energy at scission(E*_(sc)) measured in experiments.It is found that the postsaddle dissipation strength required to fit E*_(sc) data is 12*10~(21) s~(-1)for~(254;256)Fm and 6*10~(21) s~(-1)for~(189)Au,which has a smaller postsaddle deformation than the former heavy nucleus,showing a rise of nuclear dissipation strength with increasing deformation.
引文
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11.J.Sadhukhan,S.Pal,Critical comparison of Kramers’fission width with the stationary width from the Langevin equation.Phys.Rev.C 79,064606(2009).doi:10.1103/Phys Rev C.79.064606
12.W.Ye,Heavy-ion versus3He/4He fusion-fission reactions:Angular momentum dependence of dissipation in nuclear fission.Phys.Rev.C 84,034617(2011).doi:10.1103/Phys Rev C.84.034617
13.V.Singh,B.R.Behera,Maninder Kaur et al.,Neutron multiplicity measurements for19F?194;196;198Pt systems to investigate the effect of shell closure on nuclear dissipation.Phys.Rev.C 87,064601(2013).doi:10.1103/Phys Rev C.87.064601
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19.Jhilam Sadhukhan,Santanu Pal,Role of saddle-to-scission dynamics in fission fragment mass distribution.Phys.Rev.C 84,044610(2011).doi:10.1103/Phys Rev C.84.044610
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22.H.J.Krappe,K.Pomorski,Theory of Nuclear Fission.Lecture Notes in Physics Vol.838(Springer,Berlin,2012)
23.W.Ye,N.Wang,Significant role of level-density parameters in probing nuclear dissipation with light-ion-induced fission excitation functions.Phys.Rev.C 87,014610(2013).doi:10.1103/Phys Rev C.87.014610
24.B.B.Back,D.J.Blumenthal,C.N.Davids et al.,Fission hindrance in hot216Th:evaporation residue measurements.Phys.Rev.C 74,044602(1999).doi:10.1103/Phys Rev C.74.044602
25.P.D.Shidling,N.M.Badiger,S.Nath et al.,Fission hindrance studies in200Pb:evaporation residue cross section and spin distribution measurements.Phys.Rev.C 60,064603(1999).doi:10.1103/Phys Rev C.60.064603
26.K.Ramachandran,A.Chatterjee,A.Navin et al.,Fission time scale from prescission neutron,proton,and a particle multiplicities in28Si?175Lu.Phys.Rev.C 73,064609(1999).doi:10.1103/Phys Rev C.73.064609
27.W.Ye,N.Wang,Spallation reaction and the probe of nuclear dissipation with excitation energy at scission.Nucl.Sci.Tech.24,050521(2013)
28.P.Fro¨brich,On the dynamics of fission of hot nuclei.Nucl.Phys.A 787,170(2007).doi:10.1016/j.nuclphysa.2006.12.028
29.P.Mo¨ller,W.D.Myers,W.J.Swiatecki et al.,Nuclear mass formula with a finite-range droplet model and a folded-Yukawa single-particle potential.At.Data Nucl.Data Tables 39,225(1988).doi:10.1016/0092-640X(88)90023-X
30.A.V.Ignatyuk,M.G.Itkis,V.N.Okolovich et al.,Fission of preactinide nuclei.Excitation functions for the(a;f)reaction.Yad.Fiz.21,1185(1975)
31.I.I.Gontchar,P.Fro¨brich,Consistent dynamical and statistical description of fission of hot nuclei.Phys.Rev.C 47,2228(1999).doi:10.1103/Phys Rev C.47.2228
32.M.Blann,Decay of deformed and superdeformed nuclei formed in heavy ion reactions.Phys.Rev.C 21,1770(1980).doi:10.1103/Phys Rev C.21.1770
33.C.Schmitt,P.N.Nadtochy,A.Heinz et al.,First experiment on fission transients in highly fissile spherical nuclei produced by fragmentation of radioactive beams.Phys.Rev.Lett 99,042701(2007).doi:10.1103/Phys Rev Lett.99.042701
34.W.Ye,H.W.Yang,F.Wu,Isospin effects on the evaporation residue spin distribution.Phys.Rev.C 77,011302(R)(2008).doi:10.1103/Phys Rev C.77.011302
35.B.Jurado,C.Schmitt,K.-H.Schmidt et al.,Transient effects in fission from new experimental signatures.Phys.Rev.Lett 93,072501(2004).doi:10.1103/Phys Rev Lett.93.072501
36.D.J.Hinde,Neutron emission as a probe of fusion-fission and quasifission dynamics.Phys.Rev.C 45,1229(1992).doi:10.1103/Phys Rev C.45.1229
37.J.Cabrera,Th Keutgen,Y.El Masri et al.,Fusion-fission and fusion-evaporation processes in20Ne?159Tb and20Ne?169Tm interactions between E/A=8 and 16 Me V.Phys.Rev.C 68,034613(2003).doi:10.1103/Phys Rev C.68.034613
2.J.U.Andersen,J.Chevallier,J.S.Forster et al.,Attosecond time delays in heavy-ion induced fission measured by crystal blocking.Phys.Rev.C 78,064609(2008).doi:10.1103/Phys Rev C.78.064609
3.W.Q.Shen,J.Albinski,A.Gobbi et al.,Fission and quasifission in U-induced reactions.Phys.Rev.C 36,115(1987).doi:10.1103/Phys Rev C.36.115
4.J.Velkovska,C.R.Morton,R.L.Mc Grath et al.,Quasifission reactions as a probe of nuclear viscosity.Phys.Rev.C 59,1506(1999).doi:10.1103/Phys Rev C.59.1506
5.E.Williams,D.J.Hinde,M.Dasgupta et al.,Evolution of signatures of quasifission in reactions forming curium.Phys.Rev.C88,034611(2013).doi:10.1103/Phys Rev C.88.034611
6.A.K.Nasirov,G.Giardina,G.Mandaglio et al.,Quasifission and fusion-fission in reactions with massive nuclei:comparison of reactions leading to the Z=120 element.Phys.Rev.C 79,024606(2009).doi:10.1103/Phys Rev C.79.024606
7.Y.Aritomo,Fusion hindrance and roles of shell effects in superheavy mass region.Nucl.Phys.A 88,034611(2013).doi:10.1016/j.nuclphysa.2006.09.018
8.J.Benlliure,E.Casarejos,J.Pereira et al.,Transient and quasistationary dissipative effects in the fission flux across the barrier in 1A Ge V238U on deuterium reactions.Phys.Rev.C 74,014609(2006).doi:10.1103/Phys Rev C.74.014609
9.H.Singh,K.S.Golda,Santanu Pal et al.,Role of nuclear dissipation and entrance channel mass asymmetry in pre-scission neutron multiplicity enhancement in fusion-fission reactions.Phys.Rev.C 78,024609(2008).doi:10.1103/Phys Rev C.78.024609
10.R.Sandal,B.R.Behera,V.Singh et al.,Effect of N/Z in prescission neutron multiplicity for16;18O?194;198Pt systems.Phys.Rev.C 87,014604(2013).doi:10.1103/Phys Rev C.87.014604
11.J.Sadhukhan,S.Pal,Critical comparison of Kramers’fission width with the stationary width from the Langevin equation.Phys.Rev.C 79,064606(2009).doi:10.1103/Phys Rev C.79.064606
12.W.Ye,Heavy-ion versus3He/4He fusion-fission reactions:Angular momentum dependence of dissipation in nuclear fission.Phys.Rev.C 84,034617(2011).doi:10.1103/Phys Rev C.84.034617
13.V.Singh,B.R.Behera,Maninder Kaur et al.,Neutron multiplicity measurements for19F?194;196;198Pt systems to investigate the effect of shell closure on nuclear dissipation.Phys.Rev.C 87,064601(2013).doi:10.1103/Phys Rev C.87.064601
14.Y.Ayyad,J.Benlliure,E.Casarejos et al.,Proton-induced fission of181Ta at high excitation energies.Phys.Rev.C 89,054610(2014).doi:10.1103/Phys Rev C.89.054610
15.P.Fro¨brich,I.I.Gontchar,Langevin fluctuation-dissipation dynamics of hot nuclei:prescission neutron multiplicities and fission probabilities.Nucl.Phys.A 556,281(1993).doi:10.1016/0375-9474(93)90352-X
16.K.Pomorski,B.Nerlo-Pomorskaa,A.Surowieca et al.,Light-particle emission from the fissioning nuclei126Ba,188Pt and 266;272;278110:theoretical predictions and experimental results.Nucl.Phys.A 679,25(2000).doi:10.1016/S0375-9474(00)00327-4
17.W.Ye,Role of N/Z in giant dipole resonance c rays as a probe of post-saddle nuclear dissipation.Phys.Lett.B 681,413(2000).doi:10.1016/j.physletb.2009.10.067
18.A.V.Karpov,P.N.Nadtochy,D.V.Vanin et al.,Three-dimensional Langevin calculations of fission fragment mass-energy distribution from excited compound nuclei.Phys.Rev.C 63,054610(2001).doi:10.1103/Phys Rev C.63.054610
19.Jhilam Sadhukhan,Santanu Pal,Role of saddle-to-scission dynamics in fission fragment mass distribution.Phys.Rev.C 84,044610(2011).doi:10.1103/Phys Rev C.84.044610
20.P.Fro¨brich,I.I.Gontchar,Langevin description of fusion,deepinelastic collisions and heavy-ion-induced fission.Phys.Rep.292,131(1998).doi:10.1016/S0370-1573(97)00042-2
21.P.N.Nadtochy,G.D.Adeev,A.V.Karpov,More detailed study of fission dynamics in fusion-fission reactions within a stochastic approach.Phys.Rev.C 65,064615(2002).doi:10.1103/Phys Rev C.65.064615
22.H.J.Krappe,K.Pomorski,Theory of Nuclear Fission.Lecture Notes in Physics Vol.838(Springer,Berlin,2012)
23.W.Ye,N.Wang,Significant role of level-density parameters in probing nuclear dissipation with light-ion-induced fission excitation functions.Phys.Rev.C 87,014610(2013).doi:10.1103/Phys Rev C.87.014610
24.B.B.Back,D.J.Blumenthal,C.N.Davids et al.,Fission hindrance in hot216Th:evaporation residue measurements.Phys.Rev.C 74,044602(1999).doi:10.1103/Phys Rev C.74.044602
25.P.D.Shidling,N.M.Badiger,S.Nath et al.,Fission hindrance studies in200Pb:evaporation residue cross section and spin distribution measurements.Phys.Rev.C 60,064603(1999).doi:10.1103/Phys Rev C.60.064603
26.K.Ramachandran,A.Chatterjee,A.Navin et al.,Fission time scale from prescission neutron,proton,and a particle multiplicities in28Si?175Lu.Phys.Rev.C 73,064609(1999).doi:10.1103/Phys Rev C.73.064609
27.W.Ye,N.Wang,Spallation reaction and the probe of nuclear dissipation with excitation energy at scission.Nucl.Sci.Tech.24,050521(2013)
28.P.Fro¨brich,On the dynamics of fission of hot nuclei.Nucl.Phys.A 787,170(2007).doi:10.1016/j.nuclphysa.2006.12.028
29.P.Mo¨ller,W.D.Myers,W.J.Swiatecki et al.,Nuclear mass formula with a finite-range droplet model and a folded-Yukawa single-particle potential.At.Data Nucl.Data Tables 39,225(1988).doi:10.1016/0092-640X(88)90023-X
30.A.V.Ignatyuk,M.G.Itkis,V.N.Okolovich et al.,Fission of preactinide nuclei.Excitation functions for the(a;f)reaction.Yad.Fiz.21,1185(1975)
31.I.I.Gontchar,P.Fro¨brich,Consistent dynamical and statistical description of fission of hot nuclei.Phys.Rev.C 47,2228(1999).doi:10.1103/Phys Rev C.47.2228
32.M.Blann,Decay of deformed and superdeformed nuclei formed in heavy ion reactions.Phys.Rev.C 21,1770(1980).doi:10.1103/Phys Rev C.21.1770
33.C.Schmitt,P.N.Nadtochy,A.Heinz et al.,First experiment on fission transients in highly fissile spherical nuclei produced by fragmentation of radioactive beams.Phys.Rev.Lett 99,042701(2007).doi:10.1103/Phys Rev Lett.99.042701
34.W.Ye,H.W.Yang,F.Wu,Isospin effects on the evaporation residue spin distribution.Phys.Rev.C 77,011302(R)(2008).doi:10.1103/Phys Rev C.77.011302
35.B.Jurado,C.Schmitt,K.-H.Schmidt et al.,Transient effects in fission from new experimental signatures.Phys.Rev.Lett 93,072501(2004).doi:10.1103/Phys Rev Lett.93.072501
36.D.J.Hinde,Neutron emission as a probe of fusion-fission and quasifission dynamics.Phys.Rev.C 45,1229(1992).doi:10.1103/Phys Rev C.45.1229
37.J.Cabrera,Th Keutgen,Y.El Masri et al.,Fusion-fission and fusion-evaporation processes in20Ne?159Tb and20Ne?169Tm interactions between E/A=8 and 16 Me V.Phys.Rev.C 68,034613(2003).doi:10.1103/Phys Rev C.68.034613