Saxena, A. ; Fabris, D. ; Prete, G. ; Shetty, D. V. ; Viesti, G. ; Nayak, B. K. ; Biswas, D. C. ; Choudhury, R. K. ; Kapoor, S. S. ; Lunardon, M. ; Moretto, S. ; Nebbia, G. ; Pesente, S. ; Rizzi, V. ; Samant, A. M. ; Barbui, M. ; Fioretto, E. ; Cinausero, M. ; Brondi, A. ; La Rana, G. ; Moro, R. ; Vardaci, E. ; Gelli, N. ; Lucarelli, F.
(2004)
*Particle multiplicities in the fission-like reactions of 340 MeV ^{28}Si on ^{232}Th*
Nuclear Physics A, 730
(3-4).
pp. 299-315.
ISSN 0375-9474

Full text not available from this repository.

Official URL: http://www.sciencedirect.com/science/article/pii/S...

Related URL: http://dx.doi.org/10.1016/j.nuclphysa.2003.11.007

## Abstract

Pre-scission and post-scission multiplicities of neutrons and alpha particles have been simultaneously measured for
the fission-like reactions of 340 MeV ^{28}Si on ^{232}Th. Dynamical model calculations using
HICOL code predict that about 90% of the observed events are of quasi-fission type while the remaining 10% are from
compound nucleus fission decay. Moving source fits were carried out to the observed neutron and alpha particle spectra,
measured at different angles with respect to the fragment directions. The pre-scission and post-scission neutron multiplicities
are deduced to be 8.7± 2.0 and 9.4± 2.0, respectively. The corresponding multiplicity values for alpha particles
are found to be 0.22± 0.08 and 0.1± 0.03. From the measured post-scission neutron multiplicity, it is inferred that
about 65±20 MeV of the initial excitation energy remains at scission. This may be compared to the value of 85±
30 MeV estimated from PACE2 statistical model calculations, adjusted to reproduce the measured pre-scission neutron
multiplicity. From a comparison of the Statistical Model predictions with the measured pre-scission neutron multiplicity, the
fission delay is estimated to be of 5^{+7}_{-3}x10^{-20} s which overlaps with the
average duration of fission-like process from the contact to the scission point (2×10^{-20} s) as determined
from HICOL-based dynamical calculations. For the delay time deduced as above, the pre-scission alpha particle multiplicity
calculated by the PACE2 code is about a factor two larger than the experimental one, demonstrating the difficulties in
modelling the alpha particle emission from highly elongated shapes that characterize the fissioning system from the contact
point to scission.

Item Type: | Article |
---|---|

Source: | Copyright of this article belongs to Elsevier Science. |

Keywords: | Fusion-fission Dynamics; Pre- and Post-scission Multiplicities; Fission Delay Time; Dynamical and Statistical Calculations |

ID Code: | 93904 |

Deposited On: | 29 Jun 2012 13:07 |

Last Modified: | 29 Jun 2012 13:07 |

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