Mass distribution and multiple fragmentation events in high energy cluster—cluster collisions: evidence for a predicted phase transition

Collision induced cluster fragmentation: From fragment size distributions to the caloric curve

“…The most famous is the Fisher droplet model [37] that allows calculate the droplet size distribution in a vapour. At the critical temperature the resulting distribution f(p) in sizes p is proportional to p -τ and the predicted exponent of 2.23 is close to the values observed for nuclear [36,38] and cluster fragmentation [28,29,[39][40][41]. These cluster collision experiments around the Bohr energy (see [29] and references therein) have shown the formation of many different fragments in the exit channel of the reaction exhibiting a power law in total fragment size distributions.…”

“…After momentum analysis by a magnetic sector field, the mass selected high energy projectile pulse (pulse length ~100 ms, With this instrument we are able to record for each event simultaneously the number (multiplicity) of each mass-identified fragment ion resulting from the interaction (for more experimental details, see [12,29,30]. In addition, for each event we can also monitor in coincidence with the detected ions the sum of the masses of all the neutral fragments.…”

“…This complete analysis allows us to go beyond the straightforward determination of total fragment size distributions as reported previously [29] and references therein), since we are able to generate for the first time partial fragment size distributions for selected decay reactions or classes of decay reactions. In high-energy cluster-cluster collision, the fragmentation of H 25 + clusters exhibits a monotonously decreasing distribution, which is typical for the Intermediate Mass Fragment (IMF) case known in nuclear physics.…”

Event-by-Event Analysis of Collision-Induced Cluster-Ion Fragmentation: Sequential Monomer Evaporation versus Fission Reactions

“…In contrast, high-energy deposition, e.g., by collisions of the clusters with high-energy heavy particles or vice versa [9][10][11][12] and by collisions of clusters with multiply charged ions [13,14], has led to bimodal fragment ion distributions which have been interpreted (i) by the presence of sequential (monomer) evaporations (see above) leading to the production of fragment ions with large masses and (ii) by the presence of multifragmentation processes leading to the formation of the fragment ions with the small masses. These bimodal distributions, sometimes exhibiting a U shape [10,12], sometimes consisting of two peaks separated by a strong minimum [9,11,13,14] have also been observed for primary mass spectra after electron impact or photon impact ionization of C 60 and after C 60 ions impacting a surface (see [15] and references therein). Moreover, these distribution patterns obtained are similar to what have been seen in nuclear fragmentation [16].…”

“…This allows us to record for each event simultaneously the number (multiplicity) of each mass-identified fragment ion resulting from the interaction (for more experimental details, see Ref. [10] and references therein). Moreover, for each event we can also monitor in coincidence with the detected ions the sum of the masses of all the neutral fragments.…”