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MO: Fachverband Molekülphysik

MO 5: MO Poster 1

MO 5.11: Poster

Montag, 9. März 2020, 17:00–19:00, Empore Lichthof

IR Photodissociation spectra of SixH4x-4⁺ (x=4-8): Evidence for Si-H-Si proton bridges — •Martin Andreas Robert George and Otto Dopfer — Institut für Optik und Atomare Physik, Technische Universität Berlin, Germany

Silicon hydride clusters (SixHy⁺) play a significant role in plasma chemistry and astrochemistry. Despite this importance their structural and energetic properties are largely unexplored. Building upon our previous investigations of Si2H6^{+ [1]}, Si2H7^{+ [2]}, Si3H8^{+ [3]}, we present infrared photodissociation (IRPD) spectra of previously unknown SixHy⁺ ions of the form SixH4x-4⁺ with x=4-8 (Si4H12⁺-Si8H24⁺) ^[4]. Our spectral analysis, supported by dispersion-corrected density functional calculations, reveals that all SixH4x-4⁺ ions have at least one Si-H-Si bridge. The characteristic fingerprint of these three-center two-electron (3c-2e) bonds is the strongly IR active antisymmetric stretch fundamental of the Si-H-Si bridge. The frequency of this vibration depends strongly on the structural and energetic details of the Si-H-Si bridge. Our investigations reveal the correlations between the properties of the various Si-H-Si bridges (bond distances, bond angles, binding energies, stretch frequencies). The bond strength varies from strong symmetric 3c-2e chemical bonds to weak hydrogen or van der Waals bonds. [1] M. Savoca et al. (2013), Phys. Chem. Chem. Phys., 15, 2774 [2] M. Savoca et al., Angew. Chem. Int. Ed. (2013), 52, 1568 [3] M.A.R. George et al., Chem. Eur. J. (2013), 19, 15315-15328 [4] M.A.R. George, O. Dopfer (2019), Int. J. Mass Spectrom. (2019), 435, 51