Experimental And Theoretical Studies On Carbon/Sulfur Binary Cluster Produced By Laser Vaporization

The dissertation is devoted to the study of formation and characterization of carbon and sulfur binary clusters. Recently, cluster science has undergone an explosive growth in activity. Clusters are aggregates of atoms or molecules ranging in size from two to tens of thousands of monomer units. Clusters are distinct from bulk materials because they are dominated by surface species, and consequently, clusters have structures and properties that often differ from anything that can be observed in the bulk. The upper size limit to what we may call a cluster has something to do with the onset of bulk behavior, and the cluster size at which bulk properties appear depends on the particular physical property chosen for study. We should emphasize here that we are concerned with the physical transformation from finite to bulk behavior, not with the mathematical transition. Clusters are not to be viewed as some finite representation of a bulk material forced to take on bulk structure with the imposition of periodic boundary conditions. The dependence of many physical properties on the size of such constrained system is weU understood using scaling relations. For true finite systems, the change in physical properties with cluster size can be erratic. The experimental and theoretical methods that are now being applied to these systems are often capable of revealing quantum state specific information and are therefore quite different from those applied in the bulk, resulting in the promise that these finite systems will provide us with fundamentally new insights into condensed phase behavior. The research for new structure of compounds or clusters of the well known elements such as carbon, sulfur, et al. are very interesting for chemists, because the unusual structure will lead to fascinating properties, even to a potential for their industrial application through extensive investigation. The study of the properties is often attractive from both the fundamental and the aesthetical points of view. Typical examples can be found in the area of condensed phases of small molecular species which have been prepared by using various experimental techniques: the discovery and synthesis of the perfect symmetrical C~, Metal-car and so on. Spectroscopic investigation of the clusters combined with theoretical study has become an active field of research in the last decades. Hand in hand with the advances in experimental studies, there has been much progress in efforts to derive theoretical models for larger C/S binary clusters. The combined efforts of experimentalists and theoreticians have led to a detailed physical insight into the microscopic interactions that govern the structural and dynamic behavior of these clusters. In this thesis, all the experiments were performed on a homemade tandem time- of-flight mass spectrometer equipped with a pulsed laser. The pulsed laser beam employed in the experiment is the second harmonic of a Nd:YAG laser. The first pulsed acceleration field of the mass spectrometer was applied at 950V. Mass resolution of the first stage of the tandem mass spectrometer exceeds 400 and the second one is near 100. The acceleration voltage applied in the second stage is 3000V. When the gas valve is inactive, the whole vacuum system operates under a vacuum of 10.6 Torr. The interested cluster ions were selected by a pulsed 搈ass gate?and crossed with a pulsed gas beam. Kinetic energy of the cluster ions was adjusted between 50 and 200 eV after decelerating for collisions.