Ab initio calculations to support accurate modelling of the rovibronic spectroscopy calculations of vanadium monoxide (VO)

Abstract

Accurate knowledge of the rovibronic near-infrared and visible spectra of vanadium monoxide (VO) is very important for studies of cool stellar and hot planetary atmospheres. Here, the required ab initio dipole moment and spin-orbit coupling curves for VO are produced. This data forms the basis of a new VO line list considering 13 different electronic states and containing over 277 million transitions. Open shell transition, metal diatomics are challenging species to model through ab initio quantum mechanics due to the large number of low-lying electronic states, significant spin-orbit coupling and strong static and dynamic electron correlation. Multi-reference configuration interaction methodologies using orbitals from a complete active space self-consistent-field (CASSCF) calculation are the standard technique for these systems. We use different state-specific or minimal-state CASSCF orbitals for each electronic state to maximise the calculation accuracy. The off-diagonal dipole moment controls the intensity of electronic transitions. We test finite-field off-diagonal dipole moments, but found that (1) the accuracy of the excitation energies were not sufficient to allow accurate dipole moments to be evaluated and (2) computer time requirements for perpendicular transitions were prohibitive. The best off-diagonal dipole moments are calculated using wavefunctions with different CASSCF orbitals.

Molecular Physics, 2016

References in corpus (3)

• A search for TiO in the optical high-resolution transmission spectrum of HD 209458b: Hindrance due to inaccuracies in the line database
• The calculated rovibronic spectrum of scandium hydride, ScH
• Applying Monte Carlo configuration interaction to transition metal dimers: exploring the balance between static and dynamic correlation

Cited by in corpus (11)

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• MARVEL analysis of the measured high-resolution rovibronic spectra of ${}^{48}$Ti${}^{16}$O
• Laboratory spectra of hot molecules: data needs for hot super-Earth exoplanets
• Spectroscopy of YO from first principles
• Unifying High- and Low-resolution Observations to Constrain the Dayside Atmosphere of KELT-20b/MASCARA-2b
• Empirical Line Lists in the ExoMol Database
• A variational model for the hyperfine resolved spectrum of VO in its ground electronic state
• Theoretical rovibronic spectroscopy of the calcium monohydroxide radical (CaOH)
• An empirical spectroscopic model for eleven electronic states of VO