Neal Colleen M, Starace Anne K, Jarrold Martin F
Chemistry Department, Indiana University, Bloomington, Indiana 47405, USA.
J Am Soc Mass Spectrom. 2007 Jan;18(1):74-81. doi: 10.1016/j.jasms.2006.08.019. Epub 2006 Sep 28.
Calorimetry measurements have been used to probe the melting of aluminum cluster cations with 63 to 83 atoms. Heat capacities were determined as a function of temperature (from 150 to 1050 K) for size-selected cluster ions using an approach based on multicollision-induced dissociation. The experimental method is described in detail and the assumptions are critically evaluated. Most of the aluminum clusters in the size range examined here show a distinct peak in their heat capacities that is attributed to a melting transition (the peak is due to the latent heat). The melting temperatures are below the bulk melting point and show enormous fluctuations as a function of cluster size. Some clusters (for example, n = 64, 68, and 69) do not show peaks in their heat capacities. This behavior is probably due to the clusters having a disordered solid-like phase, so that melting occurs without a latent heat.
