Updated ro-vibrational MARVEL levels for ammonia 14NH3

An extended list of empirical ro-vibrational energy levels for the ammonia isotopologue 14 NH 3 is constructed using the MARVEL procedure. The final transition set includes 69710 experimental line positions from 97 experimental sources covering the wavenumber range below 18177 cm −1 and rotational excitations up to J = 29 . The transition set incorporates 23844 newly collated experimental transitions extending the covered energy range beyond 7500 cm −1 , yielding 10753 empirical energy levels with uncertainties, an increase of 5817 from the previous MARVEL study. This MARVEL set is then used to reMARVELise the CoYuTe line list for 14 NH 3 , yielding a total of 641836 experimentally accurate line positions. The updated line list is available from www.exomol.com . • A MARVEL set of accurate ro-vibrational energies for ammonia is constructed. • It contains 10753 empirical energy levels with uncertainties. • It is used to improve the variationally computed line list CoYuTe. • This results in 641836 accurate line positions of ammonia with ab initio intensities.