Structure And Optical Properties Of The <span Class="roman">si</span>_{<span Class="roman">4</span>}<span Class="roman">c</span>_{<span Class="roman">2</span>}^{<span Class="roman">+</span>} Cation

The chemistry of matter surrounding stars depends strongly on the elements that the center star produces during its lifetime but also on the transport of these elements to the outer layers of the star. Stars like IRC+\,10216 transport large amounts of carbon into their outer layers creating a carbon/oxygen ratio \textgreater 1. Thus not all C is bound into carbon monoxide and a variety of carbonaceous molecules like silicon carbides can form. Small molecules like \chem{SiC}, \chem{SiC_2}, \chem{SiC_3}, \chem{SiC_4}, \chem{Si_2C} but also $\mu$m-sized silicon carbide dust grains have been observed around these stars, but intermediates remain unknown. In this contribution, we concentrate on \chem{Si_4C_2^+} as an example for a possible grain seed. We present the first gas phase UV/VIS spectrum of the \chem{Si_4C_2^+} cation obtained by photodissociation spectroscopy in the range 208–330\,nm and compare the experimental results with possible ground state structures and vertical absorption spectra obtained via DFT and TD-DTF calculations.$^{[1]}$\\ \newline [1]M. Förstel et al., J. Mol. Spectrosc., 2021, 377, 11142