Intermediate-state decay rates in the exciton model

Gadioli, E.; Erba, E. Gadioli; Sona, P.

doi:10.1016/0375-9474(73)90414-4

Cited by 168 publications

(78 citation statements)

References 23 publications

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“…It is worth noting that the same value of kuFp follows from HYBRID model analyses of p-induced reactions with no = 3 and EF = 30 MeV [20]. From the corresponding EXCITON model predictions Gadioli et al [21,22] deduce a value kMFp=4 employing no=3 and a finite hole depth EF= 20 MeV, together with an energy dependent s.p. state density g(e)~l/(1--e/EF) for holes and a constant one for particles.…”

Section: Discussionmentioning

confidence: 72%

Analysis of inclusive nucleon spectra fromp- and?-induced reactions in the frame of the INDEX model, and implications for stopped ??-induced reactions

Ernst

Friedland

Stockhorst

1987

Z. Physik A - Atomic Nuclei

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The previously published INDEX model is tested for nucleon spectra from p-and einduced reactions. The results of two alternative versions, the INCLUSIVE INDEX model and the EXCLUSIVE INDEX model, quite well agree with the data. It is found that in the INCLUSIVE INDEX model three preequilibrium stages are sufficient to describe single-and multi-nucleon emission. The model provides an useful first order estimate of the influence of the finite Fermi energy on particle spectra. This effect is very strong for nucleon induced reactions while for c~-induced reactions it can be neglected. The deduced mean-free-path multiplier corroborates the long stated discrepancy between models in which excitons interact independently or not. Using preequilibrium parameters similar to those found for nucleon induced reactions the important branching ratio of contributing np and pp pairs in stopped r~--absorption can be determined by INDEX model calculations. Deduced values from published n-and p-spectra agree reasonably well with those of other experimental analyses but deviate significantly from microscopic model predictions.

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Section: Discussionmentioning

confidence: 72%

Analysis of inclusive nucleon spectra fromp- and?-induced reactions in the frame of the INDEX model, and implications for stopped ??-induced reactions

Ernst

Friedland

Stockhorst

1987

Z. Physik A - Atomic Nuclei

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“…Our cross section calculations include the Moldauer approximation for the width fluctuation correction (Moldauer 1976), and a simple exciton model for pre-equilibrium emission (Cline & Blann 1971). Pre-compound emission rates for nucleons and alpha particles are determined in accordance with (Gadioli et al 1973) and (Milazzo-Colli & Braga-Marcazzan 1973), respectively. Pre-equilibrium emission only becomes significant in this isoptopic region for incident neutron energies above ∼5 MeV, and hence will not affect neutron capture.…”

Section: Statistical Model Input Parametersmentioning

confidence: 99%

59Fe(n,g)60Fe and 60Fe(n,g)61Fe Reaction Rates from Local Systematics

Kelley¹,

Hoffman²,

Drake³

2005

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“…is related to the single-particle level density g(e) by the definition [9]: (3) j=l where ~/= ei -~F(gj = ~F -Q) is the energy of i-th particle (j-th hole) at the corresponding single-particle level and er is the Fermi energy.…”

Section: )Ph(e )mentioning

confidence: 99%

Fixed exciton number level density for a finite potential well

Shlomo

Bogila

Kolomietz

et al. 1995

Z. Physik A - Hadrons and Nuclei

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Abstract. We present a calculation of the nuclear level density e)ph(E) for a fixed number of particles p and holes h, taking into account the energy dependence of the singleparticle level density g (s). We demonstrate the significant effects of the finite depth of the potential well (continuum effect) and the finite surface thickness of the nucleus on the value of COph(E). 24.10; 21.10 The essential element of the exciton model of nuclear reactions is the level density con(E) of the nucleus in a state with excitation energy E and n excited quasiparticles. The value of con(E) depends crucially on the single-particle level density 9(8). Usually the assumption of a constant single-particle level density is made to obtain the density con(E) in a convenient analytical form [1][2][3][4][5]. Some generalization can be done taking into account a slow a-dependence of g(a) at the Fermi energy [6]. We add that in [7] g(e) was assumed to be constant inside the potential and zero outside the well. These approaches provide a good approximation in the low energy region, where the influence of the finite depth of the potential well can be neglected. However, increasing the excitation energy E leads to an increase of the partial contribution of high excited single-particle states into c0n(E). Discretizing the continuum states, by adopting an infinite potential well, by putting the nucleus in an infinite box or by locating the energies of the single-particle resonances leads to a singleparticle level density g(a) which increases with a in the continuum region. This increase of g(a) with s is rather spurious and it is due to the fact that g(s) includes the contribution of the free gas states. In fact, with the subtraction of the contribution of the free gas states, g(e), for a (realistic) finite potential well, such as a Woods Saxon potential, actually decreases with s in the continuum region [8]. This has been demonstrated recently [8], in an exact quantum mechanical calculation, using a Green's function approach for calculating g(s) in the continuum, for a finite potential well, such as a Woods-Saxon potential. Therefore, a proper accounting of the continuum states, i.e. the decrease of g(e) with e, and the effect of the diffuseness of the potential well should be taken into account in determining con(E), especially for the case of a low-number of quasiparticle configurations. We point out that in [7], where a finite potential well was considered, the contribution from the continuum states was omitted. The aim of this paper is to investigate the influence of the finite depth (i.e., effects of the continuum) and the diffuseness of the single-particle potential on the particle-hole excitation density. We adopt for this purpose a finite potential well of a trapezoidal form. It has been shown that for this potential one has for g(e): (i) An excellent agreement with g(a) obtained from a corresponding Woods-Saxon well; (ii) The Thomas-Fermi approximation, gTP(s), provides an excellent approximation to the smooth level density, g~(a...

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Intermediate-state decay rates in the exciton model

Cited by 168 publications

References 23 publications

Analysis of inclusive nucleon spectra fromp- and?-induced reactions in the frame of the INDEX model, and implications for stopped ??-induced reactions

Analysis of inclusive nucleon spectra fromp- and?-induced reactions in the frame of the INDEX model, and implications for stopped ??-induced reactions

59Fe(n,g)60Fe and 60Fe(n,g)61Fe Reaction Rates from Local Systematics

Fixed exciton number level density for a finite potential well

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