LEVEL 8.0
The file 23Na-35Cl is the level input used to create the line list for the parent isotopologue 23Na-35Cl, it can be changed for other isotopologues.
The dipole moment curves (DMC) were determined using high-level ab initio calculations, performed using MOLPRO (Werner et al. 2010). The final NaCl DMC was computed using an aug-cc-pCVQZ-DK basis set and the CCSD(T) method, where both core-valence and relativistic effects were also taken into account. The electric dipole moments were obtained using the finite field method. The ab initio DMC grid points were used directly in LEVEL. The PECs were refined by fitting to the spectroscopic data. However, extending the temperature range of the spectra required consideration of highly excited levels and extrapolation of the PECs beyond the region determined by experimental input values. Multiple potential energyu forms were tested, namely the extended Morse oscillator (EMO), Morse long range (MLR) and Morse Lennard Jones potentials, to achieve an optimum fit.
The original NaCl ExoMol line lists of Barton et al. computed using LEVEL have been truncated by removing transitions with Δv ≥ 8. This is due to a numerical problem identified by Medvedev and co-workers with the intensities of high overtone transitions computed with LEVEL.