20
M. Herman et al.
distributions can be calculated for emissions in the continuum region. Exclusive
quantities can also be calculated for simple emission channels (xn, xp, np).
Level densities can be described by three phenomenological models—the
Gilbert–Cameron model [15], the generalized superfluid model [16], or the
enhanced generalized superfluid model [17]—or by a model based on Hartree–
Fock–Bogoliubov levels [18]. The level densities are parametrized or normalized
to reproduce the average parameters of the neutron resonances and the data on the
cumulative number of low-lying nuclear levels.
Several options exist for the gamma-ray strength functions in the statistical
decay. These include the enhanced generalized Lorentzian [19], several modified Lorentzians [20, 21], the generalized Fermi-liquid model [22], the standard
Lorentzian [23], and single-particle Weisskopf estimates. These are normalized
internally to experimental gamma-ray strength functions, when available.
At higher incident energies, pre-equilibrium emission becomes important. Models available in EMPIRE for the description of these reactions are:
• the Tamura-Udagawa-Lenske multistep direct reaction model, as implemented in
ORION + TRISTAN [24, 25];
• the Nishioka-Verbaarschot-Weidenmüller-Yoshida multistep compound model
with γ -emission [26];
• the standard single-emission exciton model, as implemented in PCROSS;
• the Iwamoto-Harada model for complex particle emission [27, 28], also implemented in PCROSS; and
• the hybrid Monte Carlo simulation model, which permits multiple preequilibrium emissions, as implemented in the code DDHMS [29–31].
These models need not be executed exclusively. Thus, for example, it is possible to
calculate pre-equilibrium neutron emission using ORION + TRISTAN and the preequilibrium emission of light charged particle using PCROSS, among other possible
combinations.
3.3 Fission
EMPIRE contains both simple and sophisticated models of fission.
• The Sierk model can be used for light particle or heavy-ion induced fission [32].
• For incident light particles or photons, one can use an optical model for
transmission through multi-humped fission barriers parametrized analytically or
defined numerically, as well as multi-modal fission [33].
• Finally, prompt fission neutron spectra can be calculated using either the
Madland–Nix [34] or the Kornilov [35] model.
M. Herman et al.
distributions can be calculated for emissions in the continuum region. Exclusive
quantities can also be calculated for simple emission channels (xn, xp, np).
Level densities can be described by three phenomenological models—the
Gilbert–Cameron model [15], the generalized superfluid model [16], or the
enhanced generalized superfluid model [17]—or by a model based on Hartree–
Fock–Bogoliubov levels [18]. The level densities are parametrized or normalized
to reproduce the average parameters of the neutron resonances and the data on the
cumulative number of low-lying nuclear levels.
Several options exist for the gamma-ray strength functions in the statistical
decay. These include the enhanced generalized Lorentzian [19], several modified Lorentzians [20, 21], the generalized Fermi-liquid model [22], the standard
Lorentzian [23], and single-particle Weisskopf estimates. These are normalized
internally to experimental gamma-ray strength functions, when available.
At higher incident energies, pre-equilibrium emission becomes important. Models available in EMPIRE for the description of these reactions are:
• the Tamura-Udagawa-Lenske multistep direct reaction model, as implemented in
ORION + TRISTAN [24, 25];
• the Nishioka-Verbaarschot-Weidenmüller-Yoshida multistep compound model
with γ -emission [26];
• the standard single-emission exciton model, as implemented in PCROSS;
• the Iwamoto-Harada model for complex particle emission [27, 28], also implemented in PCROSS; and
• the hybrid Monte Carlo simulation model, which permits multiple preequilibrium emissions, as implemented in the code DDHMS [29–31].
These models need not be executed exclusively. Thus, for example, it is possible to
calculate pre-equilibrium neutron emission using ORION + TRISTAN and the preequilibrium emission of light charged particle using PCROSS, among other possible
combinations.
3.3 Fission
EMPIRE contains both simple and sophisticated models of fission.
• The Sierk model can be used for light particle or heavy-ion induced fission [32].
• For incident light particles or photons, one can use an optical model for
transmission through multi-humped fission barriers parametrized analytically or
defined numerically, as well as multi-modal fission [33].
• Finally, prompt fission neutron spectra can be calculated using either the
Madland–Nix [34] or the Kornilov [35] model.