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A theoretical model for isotopologues of beryllium monohydride, BeH, BeD and BeT, A ${}^{2}{\rm{\Pi }}$ to X ${}^{2}{{\rm{\Sigma }}}^{+}$ visible and X ${}^{2}{{\rm{\Sigma }}}^{+}$ to X ${}^{2}{{\rm{\Sigma }}}^{+}$ infrared rovibronic spectra is presented. The MARVEL procedure is used to compute empirical rovibronic energy levels for BeH, BeD and BeT, using experimental transition data for the X ${}^{2}{{\rm{\Sigma }}}^{+}$, A ${}^{2}{\rm{\Pi }}$, and C ${}^{2}{{\rm{\Sigma }}}^{+}$ states. The energy levels from these calculations are then used in the program Duo to produce a potential energy curve for the ground state, X ${}^{2}{\rm{\Sigma }}$, and to fit an improved potential energy curve for the first excited state, A ${}^{2}{\rm{\Pi }}$, including a spin–orbit coupling term, a Λ-doubling state to state (A–X states) coupling term, and Born–Oppenheimer breakdown terms for both curves. These, along with a previously computed ab initio dipole curve for the X and A states are used to generate vibrational-rotational wavefunctions, transition energies and A-values. From the transition energies and Einstein coefficients, accurate assigned synthetic spectra for BeH and its isotopologues are obtained at given rotational and vibrational temperatures. The BeH spectrum is compared with a high resolution hollow-cathode lamp spectrum and the BeD spectrum with high resolution spectra from JET giving effective vibrational and rotational temperatures. Full A–X and X–X line lists are given for BeH, BeD and BeT and provided as supplementary data on the ExoMol website.

Recently a new ammonia line list BYTe was reported comprising more than 1.1 billion transitions and designed for temperatures up to 1500 K. In this study we present an application of this line list for modelling spectra of cool star. We generated oscillator strengths of NH3 using BYTe for a frequency range of 1–5 µm and applied it for computing synthetic spectra of cool carbon giants using the WITA program. A possibility of detection of ammoniain spectra of cool carbon giants is discussed.

Published high-resolution rotation-vibration transitions of H212C16O, the principal isotopologue of methanal, are analyzed using the MARVEL (Measured Active Rotation-Vibration Energy Levels) procedure. The literature results are augmented by new, high-accuracy measurements of pure rotational transitions within the ground, ν3, ν4, and ν6 vibrational states. Of the 16 596 non-redundant transitions processed, which come from 43 sources including the present work, 16 403 could be validated, providing 5029 empirical energy levels of H212C16O with statistically well-defined uncertainties. All the empirical rotational-vibrational energy levels determined are used to improve the accuracy of ExoMol's AYTY line list for hot formaldehyde. The complete list of collated experimental transitions, the empirical energy levels determined, as well as the extended and improved line list are provided as Supplementary Material.