Variational analysis of HF dimer tunneling rotational spectra using an ab initio potential energy surface

[Display omitted] •Variational nuclear motion calculations for HF dimer using an accurateab initioPES are presented.•Good agreement is found between computed and observed rotational constants.•3 new J-branches in an HF dimer tunneling-rotation spectra recorded 30 years are identified. A very accurate, (HF)2 potential energy surface (PES) due to Huang et al. (J. Chem. Phys., 150, 154302 (2019)) is used to calculate the energy levels of the HF dimer by solving the nuclear-motion Schrödinger equation using variational program WAVR4. Calculations on an extended range of rotational states show very good agreement with experimental data. In particular the known empirical rotational constants for the ground and some observed excited vibrational states are reproduced with an accuracy of about 50 MHz. This level of accuracy is shown to extend to higher excited inter-molecular vibrational states v and higher excited rotational quantum numbers (J,Ka). These calculations allow the assignment of 3 new J-branches in an HF dimer tunneling-rotation spectra recorded 30 years ago. These branches belong to excited Ka= 4 state of the ground vibrational state, and Ka= 0 states of excited inter-molecular vibrational states.