New insight into power-law behavior of fragment size distributions in the C₆₀ multifragmentation regime

Previous experimental work has shown that a phase transition in C60 multifragmentation induced by nanosecond laser occurs at almost constant temperature covering a wide range of laser fluency. Here the relative yields of ionic fragments (IFs) C(n)(+) (n = 1-20) resulting from the multifragmentation are measured within the phase transition region. By excluding two small IFs and magic IFs due to their abnormal behavior, the data for residual IFs are used to estimate the size distributions of primary intermediate-mass IFs in the multifragmentation regime. The distributions are found to obey power laws n(-τ). Furthermore, the exponent τ values have sensitive dependence on lower laser fluency and converge to a constant of about 2.4 ± 0.2 for larger fluencies. These observations are in good agreement with an explanation based on the Fisher droplet model, offering the tantalizing possibility of a liquid-to-gas phase transition in C60 systems.