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aThe photoinduced dynamics of the fully halogenated cyclopentadienes C 5 Cl 6 and C 5 Br 6 have been investigated in solution and gas phase by femtosecond time-resolved spectroscopy. Both in solution and in gas phase, homolytic dissociation into a halogen radical and a C 5 X 5 (X = Cl, Br) radical was observed.In liquid phase, solvent-dependent formation of charge transfer complexes between geminate radicals was observed for the first time. These complexes were found to be surprisingly stable and offered the opportunity to follow the dynamics of specific radical pairs. In the case of C 5 Cl 6 in trichloroethanol, a reaction of the chlorine radical with molecules from the solvent cage was observed.

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.