<span class="roman">Si</span>_{<span class="roman">n</span>}<span class="roman">O</span>_{<span class="roman">m</span>}^{<span class="roman">+</span>} – OPTICAL ABSORPTION AND PHOTODISSOCIATION PROPERTIES

Abstract

Interstellar dust contains to a large extent µm-sized silicate particles. The origin and evolutionary processes of these are still poorly understood. Only one possible precursor, molecular SiO in a circumstellar disk, has been observed so far. [1] We present experimental data and quantum chemical calculations on the absorption and dissociation properties of small Si n O + m clusters (n = 10 − 12, m = 1 − 2) that are potential intermediates between the circumstellar SiO diatomic molecule and silicate grains observed in the interstellar medium. The spectra are the first optical absorption spectra of Si n O + m cations and obtained by photodissociation of mass-selected ions generated in a laser desorption source. [2] We compare our experimental results to TD-DFT calculations and discuss them in an astrophysical context.