High-level theoretical spectroscopic parameters for three ions of astrochemical interest

Christopher Stein, Oskar Weser, Benjamin Schröder, Peter Botschwina

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9 Scopus citations


The equilibrium geometry and rovibrational spectroscopic parameters of the three astrochemical ions l-C3H+, l-SiC2H+, and C3N- and some of their isotopologues are obtained from high-level quantum chemical calculations. A composite approach based on the explicitly correlated coupled-cluster method CCSD(T)-F12b, that further includes core correlation, scalar-relativistic effects and most importantly higher order correlation beyond CCSD(T) is used to set-up the near-equilibrium potential energy surface (PES). The spectroscopic parameters of these linear tetra-atomic ions are then extracted from these PESs by vibrational perturbation theory of second order (VPT2). Calculation of absolute intensities is also carried out for the stretching frequencies of the cations in order to identify the bands that are most likely to be detected. The importance of the accurate calculation of the rotational constants B0 and D0 for astrochemistry is discussed as well as the limits of VPT2 in this context and reasons for these limitations.

Original languageEnglish
Pages (from-to)2169-2178
Number of pages10
JournalMolecular Physics
Issue number15-16
StatePublished - 18 Aug 2015
Externally publishedYes


  • anharmonic frequencies
  • astrochemistry
  • molecular ions
  • vibrational perturbation theory


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