Singlet excited states of silicon-containing anions relevant to interstellar chemistry.

As the number of anions detected in the interstellar medium (ISM) increases, knowledge of their chemical properties is crucial in expanding our understanding of the chemistry of space. In this work we build on a previous study done in our group to examine the excited-state properties of five anions likely to exist in the ISM: SiCCN(-), CSiCN(-), CCSiN(-), SiCN(-), and SiNC(-). Our coupled cluster results indicate that SiCCN(-) and SiNC(-) possess dipole-bound singlet excited states while SiCCN(-) also has one valence state and CCSiN(-) potentially has two. Nearly all of the associated transition energies fall within the visible to near-IR region of the electromagnetic spectrum, making them applicable to the study of phenomena such as the diffuse interstellar bands.