Need for new physics in statistical models of nuclear de-excitation

G, La Rana; Dj, Moses; We, Parker; Kaplan, M.; Logan, D.; Lacey, R.; Jm, Alexander; Rj, Welberry

doi:10.1103/physrevc.35.373

Cited by 63 publications

(44 citation statements)

References 16 publications

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“…Several attempts have been made in the past few years to explain this anomaly. Some of the authors [2,3] argued that the discrepancy was due to the lowering of the emission barriers of the hot nuclei as compared to the fusion barriers for the corresponding relatively 'cold' inverse absorption channels as a result of the excitation energy and angular momentum dependent deformation of the emitting system in the former. On the other hand, there is another group of authors who claim that the anomaly may be well explained by incorporating spin dependent level density in the standard statistical model prescription and emission barriers need not be changed [4,5].…”

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confidence: 99%

“…It has been observed that the standard statistical model calculations failed to predict the shape of the evaporated α-particle energy spectra satisfactorily. A large number of experiments have been performed to study this anomaly over a wide range of compound nuclear masses A CN in the range of ∼60-170 [1][2][3][4][5][6], and in all cases it has been found that the average energies of the measured α-particle energy spectra are much lower than the corresponding theoretical predictions. Several attempts have been made in the past few years to explain this anomaly.…”

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confidence: 99%

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Evaporation ofαparticles from the31Pnucleus

Bandyopadhyay

Basu²,

Bhattacharya³

et al. 1999

Phys. Rev. C

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The energy spectra of α-particles have been measured in coincidence with the evaporation residues for the decay of the compound nucleus 31 P, produced in the reaction 19 F (96 MeV) + 12 C. The data have been compared with the predictions of the statistical model code CASCADE. It has been observed that significant deformation effect in the compound nucleus need to be considered in order to explain the shape of the evaporated α-particle energy spectra.One of the main motivations of the low energy heavy ion reactions studies has been to extract informations on the statistical properties of the hot, rotating nuclei. The informations on the main ingredients of the statistical description, i.e., the nuclear level densities and the barrier transmission probabilities, are usually obtained from the study of the evaporated light particle spectra. The validity of the statistical model depends crucially on the successful description of the light particle emission data and the model, so far, has been overwhelmingly successful in explaining a wide variety of nuclear reaction data in low energy regime. In this perspective, recent studies on the evaporated α-particle energy spectra has evoked a lot of interest (see, for example, ref.[1] and references therein). It has been observed that the standard statistical model calculations failed to predict the shape of the evaporated α-particle energy spectra satisfactorily. A large number of experiments have been performed to study this anomaly over a wide range of compound nuclear masses A CN in the range of ∼60-170 [1-6], and in all cases it has been found that the average energies of the measured α-particle energy spectra are much lower than the corresponding theoretical predictions. Several attempts have been made in the past few years to explain this anomaly. Some of the authors [2,3] argued that the discrepancy was due to the lowering of the emission barriers of the hot nuclei as compared to the fusion barriers for the corresponding relatively 'cold' inverse absorption channels as a result of the excitation energy and angular momentum dependent deformation of the emitting system in the former. On the other hand, there is another group of authors who claim that the anomaly may be well explained by incorporating spin dependent level density in the standard statistical model prescription and emission barriers need not be changed [4,5]. Moreover, it has also been observed that the magnitude of the discrepancy has some entrance channel dependence [6], the discrepancy being more for the more symmetric entrance channels. This is indicative of the fact that the magnitude of the phenomena may also be linked with the entrance channel dynamics of the system. Intuitively, the shape of the α-particle spectra would be affected by the deformation of the equilibrating system if it remains deformed over a time scale comparable to the mean life time of α emission. For heavier nuclei (A CN > 60), the theoretical calculations of shape equilibration time, using the code HICOL [1,7] show that these ti...

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confidence: 99%

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confidence: 99%

Evaporation ofαparticles from the31Pnucleus

Bandyopadhyay

Basu²,

Bhattacharya³

et al. 1999

Phys. Rev. C

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“…For the analysis of the data we used the computer code GANES developed by La Rana et al [6] and [7]. To our knowledge this is the only available code which allows to calculate particle-particle correlations, and to include the influence of quadrupole deformations of the compound nucleus.…”

Section: Data Analysis and Discussionmentioning

confidence: 99%

Influence of nuclear deformation on the correlation of protons emitted from compound nuclei

Müller

Ecker

Friese

et al. 1990

Z. Physik A - Atomic Nuclei

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“…Doubts about the correct interpretation of the experimental data came up when the measured energy spectrum of e particles [6] emitted from excited 67Ga nuclei (E* =90 MeV) was compared with calculations [13] of the statistical-model code CASCADE [,14]. In contrast to calculations [-6] performed with GANES [,11], where the experimental data could be reproduced only with the assumption of extreme compound-nucleus deformations, the CASCADE calculation describes the measured e-particle energy spectrum with the assumption of a spherical nuclear shape.…”

Section: Introductionmentioning

confidence: 97%

“…In several papers [4,[6][7][8] in which proton emission as well as e-particle emission of hot nuclei was measured simultaneously and interpreted with the computer code GANES [-11], nuclear shapes with axis ratios of 1.7 [4] to 2.5 [8] had to be assumed in order to explain the e-particle data. Even much higher deformations (axis ratio up to 3.0 and more) were necessary to describe the proton spectra at the same time.…”

Section: Introductionmentioning

confidence: 99%

Decay of the compound nucleus179Au formed in the cold fusion reaction90Zr+89Y

Gollerthan

Brohm

Clerc

et al. 1991

Z. Physik A - Hadrons and Nuclei

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For the compound nucleus 179Au formed at an excitation energy of 26 MeV in the fusion reaction 9~ 89y, the energy spectra of promptly emitted protons, e particles and 7 rays were measured in concidence with the evaporation residues. On the basis of the measured total decay energy, the 1 p and 1 e decay channels were separated from all other evaporation-residue channels. The energy spectra and absolute cross sections, together with previously measured excitation functions for various decay channels, are successfully described by statisticalmodel calculations with the Monte Carlo code CODEX.

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Need for new physics in statistical models of nuclear de-excitation

Cited by 63 publications

References 16 publications

Evaporation ofαparticles from the31Pnucleus

Evaporation ofαparticles from the31Pnucleus

Influence of nuclear deformation on the correlation of protons emitted from compound nuclei

Decay of the compound nucleus179Au formed in the cold fusion reaction90Zr+89Y

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