Eur. Phys. J. A 11, 305-310 (2001)

II. The intermediate velocity source in the ⁴⁰Ca + ⁴⁰Ca reaction at E_lab = 35 AMeV

Z. Sosin¹, R. Planeta¹, T. Ciszek¹, J. Brzychczyk¹, W. Gawlikowicz¹, K. Grotowski^{1, 2}, S. Micek¹, P. Pawlowski¹, A. Wieloch¹, A.J. Cole³, D. Benchekroun⁴, E. Bisquer⁴, A. Chabane³, M. Charvet³, B. Cheynis⁴, A. Demeyer⁴, P. Désesquelles³, E. Gerlic⁴, A. Giorni³, D. Guinet⁴, D. Heuer³, P. Lautesse⁴, L. Lebreton⁴, A. Lléres³, M. Stern⁴, L. Vagneron⁴ and J.B. Viano<sup>3

1</sup>  M. Smoluchowski Institute of Physics, Jagellonian University, Reymonta 4, 30-059 Cracow, Poland
²  H. Niewodniczanski Institute of Nuclear Physics, Radzikowskiego 152, 31-342 Cracow, Poland
³  Institut des Sciences Nucléaires de Grenoble, IN2P3-CNRS/ Université Joseph Fourier 53, Avenue des Martyrs, F-38046 Grenoble Cedex, France
⁴  Institut de Physique Nucléaire de Lyon, IN2P3-CNRS/ Université Claude Bernard 43, Boulevard du 11 Novembre 1918, F-69622 Villeurbanne Cedex, France

ufplanet@cyf-kr.edu.pl

(Received: 12 March 2001 / Revised version: 18 May 2001 Communicated by D. Guerreau)

Abstract
The shape of the velocity distributions of charged particles projected on the beam direction can be explained if emissions from the hot projectile-like fragment and the target-like fragment are supplemented by an emission from an intermediate velocity source located between them. The creation of this source is predicted by a two-stage reaction model where, in the second stage, some of the nucleons identified in the first stage as participants form a group of clusters located in the region between the colliding nuclei. The cluster coalescence process is governed on the average by the maximum value of entropy, although its fluctuations are also significant. The properties of the intermediate velocity source are precisely described, including the isotopic composition of the emitted particles.

PACS
25.70.Gh - Compound nucleus.
25.70.Lm - Strongly damped collisions.
25.70.Pq - Multifragment emission and correlations.

© Società Italiana di Fisica, Springer-Verlag 2001