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The ExoMol database (www.exomol.com) provides molecular data for spectroscopic studies of hot atmospheres. These data are widely used to model atmospheres of exoplanets, cool stars and other astronomical objects, as well as a variety of terrestrial applications. The 2024 data release reports the current status of the database which contains recommended line lists for 91 molecules and 224 isotopologues giving a total of almost 10$^{12}$ individual transitions. New features of the database include extensive "MARVELization" of line lists to allow them to be used for high resolutions studies, extension of several line lists to ultraviolet wavelengths, provision of photodissociation cross sections and extended provision of broadening parameters. Some of the in-house data specifications have been rewritten in JSON and moved to conformity with other international standards. Data products, including specific heats, a database of lifetimes for plasma studies, and the ExoMolHR web app which allows exclusively high resolution data to be extracted, are discussed.

A new silicon monoxide ($^{28}$Si$^{16}$O) line list covering infrared, visible and ultraviolet regions called SiOUVenIR is presented. This line list extends the infrared EBJT ExoMol line list by including vibronic transitions to the $A\,{}^{1}\Pi$ and $E\,{}^{1}\Sigma^{+}$ electronic states. Strong perturbations to the $A\,{}^{1}\Pi$ band system are accurately modelled through the treatment of 6 dark electronic states: $C\,{}^{1}\Sigma^{-}$, $D\,{}^{1}\Delta$, $a\,{}^{3}\Sigma^{+}$, $b\,{}^{3}\Pi$, $e\,{}^{3}\Sigma^{-}$ and $d\,{}^{3}\Delta$. Along with the $X\,{}^{1}\Sigma^{+}$ ground state, these 9 electronic states were used to build a comprehensive spectroscopic model of SiO using a combination of empirical and ab initio curves, including the potential energy (PE), spin-orbit (SO), electronic angular momentum (EAM) and (transition) dipole moment curves. The ab initio PE and coupling curves, computed at the multireference configuration interaction (MRCI) level of theory, were refined by fitting their analytical representations to 2617 experimentally derived SiO energy levels determined from 97 vibronic bands belonging to the $X$-$X$, $E$-$X$ and $A$-$X$ electronic systems through the MARVEL procedure. 112 observed forbidden transitions from the $C$-$X$, $D$-$X$, $e$-$X$, and $d$-$X$ bands were assigned using our predictions, and these could be fed back into the MARVEL procedure. The SiOUVenIR line list was computed using published ab initio transition dipole moments for the $E$-$X$ and $A$-$X$ bands; the line list is suitable for temperatures up to 10,000 K and for wavelengths longer than 140 nm. SiOUVenIR is available from www.exomol.com and the CDS database.

Phosphine is now well established as a biosignature, which has risen to prominence with its recent tentative detection on Venus. To follow up this discovery and related future exoplanet biosignature detections, it is important to spectroscopically detect the presence of phosphorus-bearing atmospheric molecules that could be involved in the chemical networks producing, destroying or reacting with phosphine. We start by enumerating phosphorus-bearing molecules (P-molecules) that could potentially be detected spectroscopically in planetary atmospheres and collecting all available spectral data. Gaseous P-molecules are rare, with speciation information scarce. Very few molecules have high accuracy spectral data from experiment or theory; instead, the best available data is from the RASCALL approach and obtained using functional group theory. Here, we present a high-throughput approach utilising established computational quantum chemistry methods (CQC) to produce a database of approximate infrared spectra for 958 P-molecules. These data are of interest for astronomy and astrochemistry (importantly identifying potential ambiguities in molecular assignments), improving RASCALL's underlying data, big data spectral analysis and future machine learning applications. However, this data will probably not be sufficiently accurate for secure experimental detections of specific molecules within complex gaseous mixtures in laboratory or astronomy settings., Comment: 36 pages, 10 figures

The ExoMol database (www.exomol.com) provides molecular data for spectroscopic studies of hot atmospheres. While the data is intended for studies of exoplanets and other astronomical bodies, the dataset is widely applicable. The basic form of the database is extensive line lists; these are supplemented with partition functions, state lifetimes, cooling functions, Land\'e g-factors, temperature-dependent cross sections, opacities, pressure broadening parameters, $k$-coefficients and dipoles. This paper presents the latest release of the database which has been expanded to consider 80 molecules and 190 isotopologues totaling over 700 billion transitions. While the spectroscopic data is concentrated at infrared and visible wavelengths, ultraviolet transitions are being increasingly considered in response to requests from observers. The core of the database comes from the ExoMol project which primarily uses theoretical methods, albeit usually fine-tuned to reproduce laboratory spectra, to generate very extensive line lists for studies of hot bodies. The data has recently been supplemented by line lists deriving from direct laboratory observations, albeit usually with the use of ab initio transition intensities. A major push in the new release is towards accurate characterisation of transition frequencies for use in high resolution studies of exoplanets and other bodies.

The GYT line list covering rotational, rovibrational and rovibronic transitions of the mercapto radical SH is presented. This work extends and replaces the SNaSH line list [Yurchenko et al., 2018, MNRAS, 478, 270] which covers the ground (electronic) $X$ $^{2}\Pi$ state only. This extension is prompted by the tentative identification of the ultra-violet features of SH as being of importance in the transmission spectrum of the ultra-hot Jupiter exoplanet WASP-121b [Evans et al., 2018, AJ., 156, 283]. This GYT line list model is generated by fitting empirical potential energy, spin-orbit and electronic angular momenta functions to experimentally measured wavelengths within the $X$ $^{2}\Pi$ and $A$ $^{2}\Sigma^{+}$ states and to the $A$ $^{2}\Sigma^{+}$ - $X$ $^{2}\Pi$ band system using ab initio curves as a starting reference point. The fits are compatible with the quoted uncertainty of the experimental data used of $\sim$ 0.03 - 0.3 cm$^{-1}$. The GYT line list covers wavelengths longer than 0.256 $\mu$m and includes 7686 rovibronic states and 572 145 transitions for $^{32}$SH. Line lists for the $^{33}$SH, $^{34}$SH, $^{36}$SH and $^{32}$SD isotopologues are generated including a consideration of non-Born-Oppenheimer effects for SD. The line lists are available from the CDS (http://cdsarc.u-strasbg.fr) and ExoMol (www.exomol.com) data bases.

Line lists for the sulphur-containing molecules SH (the mercapto radical) and NS are computed as part of the ExoMol project. These line lists consider transitions within the $X$ ${}^2\Pi$ ground state for $^{32}$SH, $^{33}$SH, $^{34}$SH and $^{\text{32}}$SD, and $^{14}$N$^{32}$S, $^{14}$N$^{33}$S, $^{14}$N$^{34}$S, $^{14}$N$^{36}$S and $^{15}$N$^{32}$S. Ab initio potential energy (PEC) and spin-orbit coupling (SOC) curves are computed and then improved by fitting to experimentally observed transitions. Fully ab initio dipole moment curves (DMCs) computed at high level of theory are used to produce the final line lists. For SH, our fit gives a root-mean-square (rms) error of 0.03 cm$^{-1}$ between the observed ($v_{\rm max}=4$, $J_{\rm max} = 34.5$) and calculated transitions wavenumbers; this is extrapolated such that all $X$ $^2\Pi$ rotational-vibrational-electronic (rovibronic) bound states are considered. For $^{\text{32}}$SH the resulting line list contains about 81000 transitions and 2300 rovibronic states, considering levels up to $v_{\rm max} = 14$ and $J_{\rm max} = 60.5$. For NS the refinement used a combination of experimentally determined frequencies and energy levels and led to an rms fitting error of 0.002 cm$^{-1}$. Each NS calculated line list includes around 2.8 million transitions and 31000 rovibronic states with a vibrational range up to $v=53$ and rotational range to $J=235.5$, which covers up to 23000 cm$^{-1}$. Both line lists should be complete for temperatures up to 5000 K. Example spectra simulated using this line list are shown and comparisons made to the existing data in the CDMS database. The line lists are available from the CDS (http://cdsarc.u-strasbg.fr) and ExoMol (www.exomol.com) data bases.

SiH has long been observed in the spectrum of our Sun and other cool stars. Computed line lists for the main isotopologues of silicon monohydride, $^{28}$SiH, $^{29}$SiH, $^{30}$SiH and $^{28}$SiD are presented. These line lists consider rotation-vibration transitions within the ground $X$ $^{2}\Pi$ electronic state as well as transitions to the low-lying $A$ $^{2}\Delta$ and $a$ $^{4}\Sigma^-$ states. Ab initio potential energy (PECs) and dipole moment curves (DMCs) along with spin-orbit and electronic-angular-momentum couplings between them are calculated using the MRCI level of theory with the MOLPRO package. The PEC for the ground X $^2\Pi$ state is refined to available experimental data with a typical accuracy of around 0.01 cm$^{-1}$ or better. The $^{28}$SiH line list includes 11,785 rovibronic states and 1,724,841 transitions with associated Einstein-A coefficients for angular momentum $J$ up to $82.5$ and covering wavenumbers up to 31340 cm$^{-1}$ ($\lambda$ $<$ 0.319 $\mu$m). Spectra are simulated using the new line list and comparisons made with various experimental spectra. These line lists are applicable up to temperatures of ~5000 K, making them relevant to astrophysical objects such as exoplanetary atmospheres and cool stars and opening up the possibility of detection in the interstellar medium. These line lists are available at the ExoMol www.exomol.com and CDS database websites.

Comprehensive line lists for phosphorus monoxide ($^{31}$P$^{16}$O) and phosphorus monosulphide ($^{31}$P$^{32}$S) in their $X$ $^2\Pi$ electronic ground state are presented. The line lists are based on new ab initio potential energy (PEC), spin-orbit (SOC) and dipole moment (DMC) curves computed using the MRCI+Q-r method with aug-cc-pwCV5Z and aug-cc-pV5Z basis sets. The nuclear motion equations (i.e. the rovibronic Schr\"odinger equations for each molecule) are solved using the program Duo. The PECs and SOCs are refined in least-squares fits to available experimental data. Partition functions, $Q(T)$, are computed up to $T=$ 5000 K, the range of validity of the line lists. These line lists are the most comprehensive available for either molecule. The characteristically sharp peak of the $Q$-branches from the spin-orbit split components give useful diagnostics for both PO and PS in spectra at infrared wavelengths. These line lists should prove useful for analysing observations and setting up models of environments such as brown dwarfs, low-mass stars, O-rich circumstellar regions and potentially for exoplanetary retrievals. Since PS is yet to be detected in space, the role of the two lowest excited electronic states ($a$ $^4\Pi$ and $B$ $^2\Pi$) are also considered. An approximate line list for the PS $X - B$ electronic transition, which predicts a number of sharp vibrational bands in the near ultraviolet, is also presented. he line lists are available from the CDS (cdsarc.u-strasbg.fr) and ExoMol (www.exomol.com) databases., Comment: MNRAS (2017)

The ExoMol database (www.exomol.com) provides extensive line lists of molecular transitions which are valid over extended temperatures ranges. The status of the current release of the database is reviewed and a new data structure is specified. This structure augments the provision of energy levels (and hence transition frequencies) and Einstein $A$ coefficients with other key properties, including lifetimes of individual states, temperature-dependent cooling functions, Land\'e $g$-factors, partition functions, cross sections, $k$-coefficients and transition dipoles with phase relations. Particular attention is paid to the treatment of pressure broadening parameters. The new data structure includes a definition file which provides the necessary information for utilities accessing ExoMol through its application programming interface (API). Prospects for the inclusion of new species into the database are discussed., Comment: 68 pages, 24 Tables, 1 figure. Updated corrects minor errors in format statements