Size Estimation and Time Evolution of Large Size Rare Gas Clusters by Rayleigh Scattering Techniques

摘要

Large rare gas clusters Arn, Krn and Xen were produced at room temperature in the process of supersonic adiabatic expansion. The cluster size is examined by a Rayleigh scattering experiment. Power variations of the average cluster size Nc with the gas backing pressure P0 give size scaling as Nc ∝ P02.0, resulting in the largest cluster sizes which are estimated in the present work to be about 1.5 × 104, 2.6 × 104 and 4.0 × 104 atoms (the corresponding diameters of the cluster spheres are about 9, 13 and 17nm) for Ar, Kr and Xe, respectively. A time resolving Rayleigh scattering experiment was conducted to investigate the time evolution of cluster formation and decay processes. A surprising two-plateau structure of the time evolution characteristic of cluster formation and decay processes of Kr and Xe clusters was revealed as compared with a "normal" single structure for the case of Ar gas. In the second plateau, the intensity of the scattered light is enhanced greatly, by even .as much as 62 timles, over that in the first plateau, indicating a significant increase in cluster size. This finding supports the importance of nuclei in the gas condensation process and may be helpful for further insight into the phenomenon of clustering.