Electronic and Rovibrational Quantum Chemical Analysis of C${}_3$P${}^{-}$: The Next Interstellar Anion?

Abstract

C${}_3$P${}^{-}$ is analogous to the known interstellar anion C${}_3$N${}^{-}$ with phosphorus replacing the nitrogen in a simple step down the periodic table. In this work, it is shown that C${}_3$P${}^{-}$ is likely to possess a dipole-bound excited state. It has been hypothesized and observationally supported that dipole-bound excited states are an avenue through which anions could be formed in the interstellar medium. Additionally, C${}_3$P${}^{-}$ has a valence excited state that may lead to further stabilization of this molecule, and C${}_3$P${}^{-}$ has a larger dipole moment than neutral C${}_3$P ($\sim 6$ D vs. $\sim 4$ D). As such, C${}_3$P${}^{-}$ is probably a more detectable astromolecule than even its corresponding neutral radical. Highly-accurate quantum chemical quartic force fields are also applied to C${}_3$P${}^{-}$ and its singly ${}^{13}$C substituted isotopologues in order to provide structures, vibrational frequencies, and spectroscopic constants that may aid in its detection.

7 pages, 4 tables, Accepted for publication in MNRAS

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