Time Scale of Fission at High Angular Momentum

Gavron, A.; Beene, J. R.; Cheynis, B.; Ferguson, R. L.; Obenshain, F. E.; Plášil, F.; Young, G. R.; Petitt, G.; Jääskeläinen, Markku; Sarantites, D. G.; Maguire, C.

doi:10.1103/physrevlett.47.1255

Cited by 87 publications

(27 citation statements)

References 17 publications

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“…[35,36] This correction, which is attributed to the presence of the nuclear medium, is sometimes characterized in terms of an effective nucleon mass m* ~ 0.5 m. [37] The resulting effective scattering cross section, a'lN = 0.5 iifV'N, determines the "classical" mean free path AO of the propagating nucleon (i. e. the mean free path if there were no blocking) or, equivalently, the "classical" collision rate Vo. This latter quantity is given by (4) Here p ~ 0.17 fm -3 is the nucleon density and g = 4 is the spin-isospin degeneracy.…”

Section: Inclusion Of Two-body Collisionsmentioning

confidence: 99%

Pre-equilibrium neutron emission in the nucleon exchange transport model

Randrup

Vandenbosch

1987

Nuclear Physics A

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LBL-23359We extend the Nucleon Exchange Transport model to include the emission of pre-equilibrium neutrons as a result of nucleon transfer to unbound states. The treatment takes account of the heating of the two nuclei caused by the energy dissipation and the cooling due to the pre-equilibrium emission. Furthermore, the transferred nucleons may induce cascading in the receptor nucleus by means of direct two-body scattering with the resident nucleons, based on a reduced, Pauli-blocked, energy-dependent free N N cross section. Qualitative agreement with experimental data is achieved, but the absolute multiplicities are systematically underestimated by about a factor of two. The dependence of multiplicity on bombarding energy is reproduced. The energy spectra and their variation with angle are generally reproduced, although the yield of the highest energy particles is sometimes underestimated.

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Section: Inclusion Of Two-body Collisionsmentioning

confidence: 99%

Pre-equilibrium neutron emission in the nucleon exchange transport model

Randrup

Vandenbosch

1987

Nuclear Physics A

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“…The success of the transition-state model of Bohr and Wheeler prevented this idea of Kramers to establish. Approximately forty years later, experimentally observed high pre-scission neutron multiplicities [11,12] gave the impetus to Grangé et al [13] to theoretically investigate the influence of dissipation on the fission time scale. Their numerical solution of the time-dependent FPE shows that it takes some time, the so-called transient time trans τ , until the current over the saddle point reaches its stationary value.…”

Section: Introductionmentioning

confidence: 99%

A critical analysis of the modelling of dissipation in fission

et al. 2005

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Abstract:The time-dependent flux over the fission barrier of an excited nucleus under the influence of dissipation is investigated. Characteristic features of the evolution of the amplitude of the probability distribution and the velocity profile at the fission barrier are derived. Analytical results are compared to numerical Langevin calculations and used to develop a new analytical approximation to the solution of the Fokker-Planck equation for the time-dependent fission-decay width. This approximation is shown to be more realistic than previously proposed descriptions, which were widely used in the past..

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“…Recent data [1][2][3][4][5][6] for a highly excited (E* > 100 MeV) heavy (A > 100 amu) CN could not be explained by this standard analysis. In particular, neutron multiplicities have been found which are 2 to 3 times bigger than the ones predicted by the statistical model.…”

Section: Introductionmentioning

confidence: 56%

“…This latter dependence was extensively analysed recently [9][10][11][12] as follows. Solving the Fokker-Planck equation one can define the time-dependent fission width F:(t) in terms of the probability flow over the saddle point [10] F:(t) = h 2:(0 = -h d in F(xo, t) (1) where F(x0, t) is the probability to find the system to the left of the saddle point Xo, that is inside the fission potential pocket. It takes some time before 2:(0 reaches the quasi-stationary value calculated by Kramers.…”

Section: Introductionmentioning

confidence: 99%

Multiplicities of charged particles prior to fission

Lanza

Weidenmüller

1986

Z. Physik A - Atomic Nuclei

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We solve time-dependent master-equations for the cascade de-excitation of the compound nucleus, taking into account the transient behaviour of the fission width. This transient behaviour is related to the nuclear friction constant, and is parametrised in terms of a delay time z. We extend recent work by Grang6, Hassani and others by including both proton and neutron evaporation. Our results show that a measurement of charged-particle multiplicities should further confine r.

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Time Scale of Fission at High Angular Momentum

Cited by 87 publications

References 17 publications

Pre-equilibrium neutron emission in the nucleon exchange transport model

Pre-equilibrium neutron emission in the nucleon exchange transport model

A critical analysis of the modelling of dissipation in fission

Multiplicities of charged particles prior to fission

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