Abstract
Multiple emission of intermediate-mass fragments (IMF) in the collisions of protons (up to 8.1 GeV), He-4 (4 and 14.6 GeV), and C-12 (22.4 GeV) on An has been Studied with the 4pi setup FASA. In all the cases, thermal multifragmentation of the hot and diluted target spectator takes place. The fragment multiplicity and charge distributions are well described by the combined model including the modified intranuclear cascade followed by the statistical multibody decay of the hot system. IMF-IMF-correlation study supports this picture, giving a very short time scale of the process (less than or equal to70 fm/c). This decay process can be interpreted as the first-order nuclear "liquid-fog" phase transition inside the spinodal region, The evolution of the mechanism of thermal multifragmentation with increasing projectile mass was investigated. The onset of the radial collective flow was observed for heavier projectiles. The analysis reveals information on the fragment space distribution inside the breakup volume: heavier IMFs are formed predominantly in the interior of the fragmenting nucleus possibly due to the density gradient. (C) 2003 MAIK "Nauka/Interperiodica".