Potential energy surface of HDO up to 25 000 cm − 1

A new spectroscopically determined potential energy surface (PES) for H D O 16 is presented. This surface is constructed by adjusting the high accuracy ab initio PES of Polyansky [ Science 299 , 539 ( 2003 )] by fitting to both published experimental data and our still unpublished data. This refinement used experimentally derived term values up to 25 000 cm − 1 and with J ⩽ 8 : a data set of 3478 energy levels once some levels with ambiguous assignment is excluded. To improve the extrapolation properties of the empirical PES, the restraint that the resulting PESs remain close to the ab initio surface was imposed. The new HDO̱07 PES reproduces the experimental data, including high J levels not included in the fit, with a root mean square error of 0.035 cm − 1 . Predictions for rotation-vibration term values up to J = 12 are made.