The Department of Physics, Stockholm University
Thursday 27 September
13:00 - 16:00
Clusters anions are complex systems which, when formed with high internal energies, can decay via fragmentation and/or electron loss and may also cool via photon emission (radiative cooling). By studying the spontaneous decay mechanisms of small metal clusters, we can gain insight into the structure and properties of these systems. Whilst the qualitative behaviour of clusters in general can be described with statistical methods the properties of small clusters depend strongly on the number of constituents. A detailed understanding of how the structure and energetics of such systems drive the cooling processes is yet to be found. This thesis presents measurements of the spontaneous decay of vibrationally excited small silver (Agn, n = 2-7) and copper clusters (Cun, n = 3-6). These measurements were performed using a single ring of the Double ElectroStatic Ion Ring ExpEriment (DESIREE) in which ions are stored in a cryogenic (~13 K) and extremevacuum (10-14 mbar) environment. The storage conditions of DESIREE enable the spontaneous decay of the silver and copper cluster anions to be followed to long time scales of up to 60 s. These long times were inaccessible until the recent development of cryogenic ion storage rings and traps. Theoretical calculations of the decay of the cluster anions were performed using a detailed balance method and these are presented and compared to the measured decay curves. Furthermore, the present measurements are compared to existing experimental results.