Comments on the state densities and the transition rates in the pre-equilibrium exciton model

Akkermans, Jos; Gruppelaar, H.

doi:10.1007/bf01432437

Cited by 20 publications

(19 citation statements)

References 22 publications

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“…The related PLD and total level density values are shown in Fig. 13(c) (Cases 11/11B) while the comparison between the two-fermion system PLD values and the ones obtained by using the two-fermion correction [32,34] is given in Fig. 13(d) (Cases 11B/11E).…”

Section: Two-component Fermi Gas Formulamentioning

confidence: 99%

Partial level densities for nuclear data calculations

Avrigeanu¹,

Avrigeanu²

1998

Computer Physics Communications

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The main formalisms of partial level densities (PLD) used in preequilibrium nuclear reaction models, based on the equidistant spacing model (ESM), are considered. A collection of FORTRAN77 functions for PLD calculation by using 14 formalisms for the related partial-state densities is provided and 28 sample cases (73 versions) are described. The results are given in graphic form too. Composite (recommended) formulas, which include the optional use of various corrections, i.e. the advanced pairing and shell correction in addition to the Pauli effect, and average energy-dependent single-particle level densities for the excited particles and holes, are also given. The formalism comprises the density of particle-hole bound states, and the effects of an exact correction for the Pauli-exclusion principle are considered. Distribution format: ASCII Keywords: Partial nuclear level density, nuclear level density, single-particle level density, equidistant-spacing model, preequilibrium emission, nuclear reactions Nature of physical problem: This Fortran code is a collection of subroutines for calculation of the partial nuclear level densities (PLD) mainly used in preequilibrium nuclear reaction models, by using 14 formalisms for the related partial state densities (PSD). PACS Method of solution:The main approaches to the calculation of the partial state density, based on the equidistant spacing model (ESM), are used. Composite (recommended) formulas including optionally various corrections, i.e. the advanced pairing and shell correction in addition to the Pauli effect, and average energy-dependent single-particle level (s.p.l.) densities for the excited particles and holes, are also involved. The density of the particle-hole bound states is moreover comprised, and the effects of an exact correction for the Pauli-exclusion principle are considered.Restrictions on the complexity of the problem: Although the quantum-mechanical s.p.l. density and the continuum effect can also be reproduced by a corresponding Fermi-gas formula, to be used accordingly within the average energy-dependent PSD in multistep reaction models, this effect is not included. The calculation of PLD with linear momentum, of first interest for modelling preequilibrium-emission angular distributions, is not available either. Typical running time:The execution time is strongly problem-dependent: it is roughly proportional to both the number of the excitation energies and the exciton configurations considered in the calculation, while consistent differences arise when various PSD formalisms are used. Twenty-eight sample cases with 73 versions which require from 0.1 to 1661 s on a PC Pentium/166MHz are provided. Unusual features of the program:The PSD functions have been optimized for their independent use, in order to provide tools for PSD/PLD users (see [5]). The related drawback is the increase in execution time, while a proper use would involve the calculation of some coefficients only once in the main program. Second, the PLD.FOR has been organized s...

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Section: Two-component Fermi Gas Formulamentioning

confidence: 99%

Partial level densities for nuclear data calculations

Avrigeanu¹,

Avrigeanu²

1998

Computer Physics Communications

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“…There have been many explanations for the inclusion of the factor C ~ 1-13-17]. However, Akkermans et al [5] have shown that the value of C ~ reduces to about 2 when the renormalized level density is used. In the present calculations we have neglected the Pauli correction (Aph=0) and have not included corrections due to pairing and shell effects.…”

Section: Emission Spectramentioning

confidence: 96%

“…Akkermans [5] has shown that the sum of (6) over ali allowed exciton numbers is asymptotically equal to the state density expression for a two component fermi gas. However, using Eq.…”

Section: P~(e)mentioning

confidence: 98%

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Statistical multistep compound reactions ? with renormalized exciton state densities

Keeni

1986

Z. Physik A - Atomic Nuclei

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The master equation which takes into account angular momentum considerations is used to obtain the emission spectra for statistical multistep compound reactions. Realistic wave functions are used to evaluate the radial integrals appearing in the escape and spreading widths. The renormalized particle hole state density of Akkermans et al. is used in the calculations. The improvements over the one component formulation are discussed.

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“…For the spin dependence of the particle-hole level density the simplified representation of Fu [10] has been adopted. Besides [7], the one-fermion type exciton-state densities have been transformed into two-fermion-like expressions using the renormalization procedure of Akkermans and Gruppelaar [11]. Finally, the intra-nuclear transition rates 2,+2,x(e) have been calculated employing the same imaginary optical model potentials as in the Hauser-Feshbach model calculations.…”

Section: The Gdh Model Including Angular Momentum and Parity Conservamentioning

confidence: 99%

Pre-equilibrium emission in neutron induced reactions on54,56Fe

Avrigeanu

Ivaşcu

Avrigeanu

1988

Z. Physik A - Atomic Nuclei

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The experimentally well known (n, p), (n, c 0 and (n, 2n) reaction excitation functions, from threshold to 20 MeV incident energy, and neutron and proton emission spectra at 14.8 MeV from s4'56Fe targets are calculated in the frame of the Geometry-Dependent Hybrid pre-equilibrium emission model, including angular momentum and parity conservation, and the Hauser-Feshbach statistical model. Use of a consistent statistical model parameter set enables the validation of the pre-equilibrium emission model. Moreover, an enhanced pre-equilibrium emission from higher spin composite system states, associated with higher incoming orbital momenta, has been evidenced. Higher orbital momenta involved also in the emergent channels of the process are suggested by calculations of the residual nuclei level populations.

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Comments on the state densities and the transition rates in the pre-equilibrium exciton model

Cited by 20 publications

References 22 publications

Partial level densities for nuclear data calculations

Partial level densities for nuclear data calculations

Statistical multistep compound reactions ? with renormalized exciton state densities

Pre-equilibrium emission in neutron induced reactions on54,56Fe

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