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Magnesium-silicates are ubiquitously found as small dust grains throughout the interstellar medium (ISM). Formed in the dense and warm environments of dying (evolved) oxygen-rich stars, they are subject to sporadic energetic processing in the diffuse ISM, where they are broken up into ultra-small silicate fragments. Such fragments likely serve as seeds for subsequent re-condensation in dense interstellar clouds but might also be highly relevant catalyst for the activation and conversion of small molecules into complex organic molecules (COMs).
In our work, we apply experimental and theoretical methods, that are well established in cluster catalysis research, to study fundamental problems of silicate dust related astrochemistry: infrared multiple-photon dissociation (IR-MPD) spectroscopy combined with ion trap and flow tube reaction studies and density functional theory (DFT) computations. With this approach we aim to gain insight into the geometric structure of ultra-small silica and silicate fragments, their potential growth through oxygen1 and/or dissociative water adsorption2 as well as their reactive and catalytic properties, especially with respect to the activation and conversion of CO2. In addition, silicate-based dust particles are likely also the origin of meteoric smoke particles (MSP) that result from dust impacting on the upper atmosphere and are thus probably involved in the formation of mesospheric ice-based noctilucent clouds (NLC). We show that highly oxidized anionic silicate clusters exhibit all the necessary chemical, electronic and optical properties to be highly credible candidates for such MSP-based NLC nucleation seeds.3 Besides structural and mechanistic studies we also aim to provide infrared spectroscopic reference data for the potential identification of such clusters in the interstellar medium (ISM) by the James Webb Space Telescope.
[1] J. Mariñoso Guiu, B.-A. Ghejan, T.M. Bernhardt, J.M. Bakker, S.M. Lang, S.T. Bromley, ACS Earth Space Chem. 6 (2022) 2465
[2] A.A. de Donato, B.-A. Ghejan, J.M. Bakker, T.M. Bernhardt, S.T. Bromley, S.M. Lang, ACS Earth Space Chem. 8 (2024) 1154
[3] J. Mariñoso Guiu, J.M. Bakker, T.M. Bernhardt, J.M.C. Plane, S.T. Bromley, S.M. Lang, npj Clim. Atmos. Sci. 8 (2025) 153
