High accuracy water potential energy surface for the calculation of infrared spectra

Abstract

Transition intensities for small molecules such as water and CO${}_2$ can now be computed with such high accuracy that they are being used to systematically replace measurements in standard databases. These calculations use high accuracy ab initio dipole moment surfaces and wavefunctions from spectroscopically-determined potential energy surfaces. Here an extra high accuracy potential energy surface (PES) of the water molecule (\hato) is produced starting from an ab initio PES which is then refined to empirical rovibrational energy levels. Variational nuclear motion calculations using this PES reproduce the fitted energy levels with a standard deviation of 0.011 \cm, approximately three times their stated uncertainty. Use of wavefunctions computed with this refined PES is found to improve the predicted transition intensities for selected (problematic) transitions. A new room temperature line list for H2(16)O is presented. It is suggested that the associated set of line intensities is the most accurate available to date for this species.

arXiv comment14 pages, 1 figure, 4 tables

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• Use of the complete basis set limit for computing highly accurate ab initio dipole moments
• The nuclear-spin-forbidden rovibrational transitions of water from first principles
• Sub-percent accuracy for the intensity of a near infrared water line at 10670 cm${}^{-1}$: experiment and analysis
• Comprehensive Quantum Calculation of the First Dielectric Virial Coefficient of Water
• Transferability and interpretability of vibrational normalizing-flow coordinates