Journal Article

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

Kyuberis, Aleksandra A., Zobov, Nikolai F., Mizus, Irina I., Tennyson, Jonathan, Polyansky, Oleg L., Makhnev, Vladimir Yu

2018

Overview

Transition intensities for small molecules such as water and CO₂ 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 wave functions from spectroscopically determined potential energy surfaces (PESs). Here, an extra high-accuracy PES of the water molecule 16 (H₂¹₆O) 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⁻¹, approximately three times their stated uncertainty. The use of wave functions computed with this refined PES is found to improve the predicted transition intensities for selected (problematic) transitions. A new room temperature line list for H₂¹₆O is presented. It is suggested that the associated set of line intensities is the most accurate available to date for this species. This article is part of the theme issue 'Modern theoretical chemistry'.

• Publisher: THE ROYAL SOCIETY