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Studies of relaxation mechanisms in argon dimers ionized by electron impact and high-resolution electron attachment to doped helium droplets / by Elias Emile Jabbour al Maalouf, MSc
AuthorJabbour al Maalouf, Elias Emile
Thesis advisorDenifl, Stephan
PublishedInnsbruck, April 2016
DescriptionXI, 110, XXXV Seiten : Illustrationen
Institutional NoteUniversität Innsbruck, Dissertation, 2016
Date of SubmissionApril 2016
Document typeDissertation (PhD)
Keywords (DE)Helium Droplets
Keywords (EN)Helium Droplets
Keywords (GND)Argon / Dimere / Ionisation
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Abstract (English)

In this dissertation, nanoscale and molecular scale investigation of some low electron ($ < $100 eV) interactions with and within clusters was conducted. The technique of supersonic expansion was used to form clusters and superfluid helium nanodroplets. These droplets were used as an isolation matrix for the formation of clusters. Electron ionization of clusters leads to different products, some of which are in an excited state and relax via interatomic relaxation channels. Electrons attach to helium droplets in two different states: an external surface state and an internal bubble state. For this investigation, two apparatuses were employed. One was a helium droplet source combined with a hemispherical electron monochromator, and a quadrupole mass spectrometer. The other was a rare gas cluster source combined with an electron impact reaction microscope. The investigation of the electron ionization of argon dimer showed evidence for two relaxation channels: the interatomic coulombic decay and radiative charge transfer. Their contribution was separated after achieving a full coincidence detection of all involved particles in the reaction. In another experiment, high-resolution electron attachment to helium atoms inside helium droplets led to the accurate determination of the positions of three resonance structures and a fourth newly identified structure. A third experiment involved electron attachment to water dimers inside helium droplets and revealed the evolution of the conduction band of helium droplets with the evolution of their size. One last investigation disclosed that the electron attachment to small water clusters gradually becomes more and more favored at slightly higher projectile electron energies as the water cluster gets larger. This observation is traced back to the difference in structure for water clusters consisting of different numbers of water molecules.

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