Eur. Phys. J. A (2010) 43: 127-130
https://doi.org/10.1140/epja/i2009-10912-5

Letter

Inadequacy of the statistical model: Some evidence for compound nuclei in the A 150 and E_x 100-200 MeV region

¹ Istituto Nazionale di Fisica Nucleare and Dipartimento di Scienze Fisiche, Università di Napoli “Federico II”, Via Cinthia, 80126, Napoli, Italy
² Istituto Nazionale di Fisica Nucleare, Via Cinthia, 80126, Napoli, Italy
³ Laboratori Nazionali di Legnaro dell’Istituto Nazionale di Fisica Nucleare, Legnaro (Padova), Italy
⁴ Istituto Nazionale di Fisica Nucleare and Dipartimento di Fisica, Padova, Italy
⁵ Istituto Nazionale di Fisica Nucleare and Dipartimento di Fisica, Firenze, Italy
⁶ Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, RU-141980, Dubna, Moscow Region, Russia

^* e-mail: moro@na.infn.it

Received: 22 July 2009
Accepted: 26 November 2009
Published online: 21 December 2009

Abstract

Light charged-particle multiplicities in the evaporation residue (ER) and fission (FF) channels from the reaction 200MeV ³²S + ¹⁰⁰Mo as well as ER and FF channel cross-sections have been measured and compared to the predictions of the statistical model (SM) to estimate the fission time scale. The statistical model fails in reproducing the whole set of data and no convincing estimate is possible. In particular, while pre-scission multiplicities can be reproduced, the model strongly overestimates proton and alpha particle multiplicities in the ER channel, irrespective of the SM input parameters and prescriptions used for the level density and the transmission coefficients. Same calculations performed on data from literature in the A 150 and excitation energy E _x 100-200 MeV region, for the ER channel, provide similar conclusions. These findings repropose the problem of the reliability of the SM in describing the compound-nucleus decay and have a relevant impact on the extraction of the fission delay time through the use of the SM.