1/f Spectra in finite atomic clusters

We study small clusters of atomic argon, Ar<SUB>7</SUB>, Ar<SUB>13</SUB>, and Ar<SUB>55</SUB>, in the temperature range when they undergo a transition from a solidlike phase to a liquidlike phase. The power spectra of potential energy fluctuations of tagged atoms in the liquid state show 1/f behavior over a wide range of frequency f, unlike either the solid phase or bulk liquid, and suggest a new experimental means of detecting cluster melting. The origin of this temporal scale invariance is explored by studying the individual potential energy distributions, which are observed to become multimodal when the clusters melt