@phdthesis{Koenig2017, author = {Stephan K{\"o}nig}, title = {Lead-cluster investigations}, journal = {Bleicluster Untersuchungen}, url = {https://nbn-resolving.org/urn:nbn:de:gbv:9-opus-21289}, pages = {79}, year = {2017}, abstract = {In this thesis, investigations on lead clusters stored in a Penning trap are presented. The measurements are performed at the ClusterTrap setup at the Institute of Physics of the University of Greifswald. A Penning trap with a superconducting magnet (B=12 Tesla) makes up the central part of the experiment. In this trap, singly positively or negatively charged lead clusters (a group of lead atoms) are stored, their amplitudes of motion are cooled, and a specific cluster size is selected. Thus, clusters of only a single size are prepared for experimental investigation. After interactions with electrons and/or photons, the trap content is extracted and analyzed by time-of-flight mass spectrometry. In the first experiment, the size-selected clusters are excited by a frequency-doubled Nd:YAG laser, which leads to fragmentation processes. The preferred fragmentation pathway, which is observed to be break-off of a seven-atom neutral cluster is unusual for metal clusters, which typically evaporate monomers. Furthermore, the already known magic cluster sizes are observed. In a subsequent experiment, positively charged lead clusters with 31 atoms are irradiated with laser light and fragmentation processes are time resolved investigated. The assumption that lead clusters fragment by break-off of neutral heptamers is confirmed. In the following experiment, an electron beam is guided through the Penning trap to ionize pulsed-in argon atoms. While the positive argon ions leave the trap, the secondary electrons are trapped together with the selected lead clusters. This allows the electrons to attach to the singly charged lead clusters, which leads to multiply negatively charged lead clusters. The relative abundance of multiply-charged clusters is measured with respect to the cluster size, from which the appearance sizes of di- and trianions can be calculated. In addition to the attachment of electrons, fragmentation products similar to those of the photoexcitation measurements are observed. Furthermore, the cluster sizes 10 and 12 are observed regardless of the investigated precursor size, together with clusters of the precursor size reduced by 10 and 12. This is a first hint for a fission process of doubly negatively charged lead clusters into two singly charged products. In a following measurement, doubly charged lead clusters are produced and photoexcited. The observed abundance spectra confirm this assumption.}, language = {en} }