Calculated line lists for H$_{\text{2}} \mkern0.1mu ^{\text{16}}$O and H$_{\text{2}} \mkern0.1mu ^{\text{18}}$O with extensive comparisons to theoretical and experimental sources including the HITRAN2016 database
Eamon K. Conway, Iouli E. Gordon, Aleksandra A. Kyuberis, Oleg L. Polyansky, Jonathan Tennyson, Nikolai F. Zobov
New line lists are presented for the two most abundant water isotopologues; H$_{2}$$^{16}$O and H$_{2}$$^{18}$O. The H$_{2}$$^{16}$O line list extends to 25710 cm$^{-1}$ with intensity stabilities provided via ratios of calculated intensities obtained from two different semi-empirical potential energy surfaces. The line list for H$_{2}$$^{18}$O extends to 20000 cm$^{-1}$. The minimum intensity considered for all is $10^{-30}$ cm molecule$^{-1}$ at 296~K, assuming 100\% abundance for each isotopologue. Fluctuation of calculated intensities caused by changes in the underlying potential energy are found to be significant, particularly for weak transitions. Direct comparisons are made against eighteen different sources of line intensities, both experimental and theoretical, many of which are used within the HITRAN2016 database. With some exceptions, there is excellent agreement between our line lists and the experimental intensities in HITRAN2016. In the infrared region, many H$_{2}$$^{16}$O bands which exhibit intensity differences of 5-10\% between to the most recent 'POKAZATEL' line list (Polyansky \textit{et al.}, [Mon. Not. Roy. Astron. Soc. \textbf{480}, 2597 (2018)] and observation, are now generally predicted to within 1\%. For H$_{2}$$^{18}$O, there are systematic differences in the strongest intensities calculated in this work versus those obtained from semi-empirical calculations. In the visible, computed cross sections show smaller residuals between our work and both HITRAN2016 and HITEMP2010 than POKAZATEL. While our line list accurately reproduces HITEMP2010 cross sections in the observed region, residuals produced from this comparison do however highlight the need to update line positions in the visible spectrum of HITEMP2010. These line lists will be used to update many transition intensities and line positions in the HITRAN2016 database.
The ExoMol database aims to provide comprehensive molecular line lists for exoplanetary and other hot atmospheres. The data are expanded by inclusion of empirically derived line lists taken from the literature for a series of diatomic molecules, namely CH, NH, OH, AlCl, AlF, OH$^+$, CaF, MgF, KF, NaF, LiCl, LiF, MgH, TiH, CrH, FeH, C$_2$, CP, CN, CaH, and triplet N$_2$. Generally, these line lists are constructed from measured spectra using a combination of effective rotational Hamiltonian models for the line positions and ab initio (transition) dipole moments to provide intensities. This work…
A methane line list for the HITEMP spectroscopic database, covering 0-13,400 cm$^{-1}$ ($>$746 nm), is presented. To create this compilation, ab initio line lists of $^{12}$CH$_{4}$ from Rey et al. (2017) ApJ, 847, 105 (provided at separate temperatures in the TheoReTS information system), are now combined with HITRAN2016 methane data to produce a single line list suitable for high-temperature line-by-line calculations up to 2000 K. An effective-temperature interpolation model was created in order to represent continuum-like features at any temperature of interest. This model is advantageous t…
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, Landé 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 an…
Any future detection of the calcium monohydroxide radical (CaOH) in stellar and exoplanetary atmospheres will rely on accurate molecular opacity data. Here, we present the first comprehensive molecular line list of CaOH covering the \A--\X\ rotation-vibration-electronic and \X--\X\ rotation-vibration bands. The newly computed OYT6 line list contains over 24.2 billion transitions between 3.2 million energy levels with rotational excitation up to $J=175.5$. It is applicable to temperatures up to $T=3000$~K and covers the 0\,--\,35\,000~cm$^{-1}$ range (wavelengths $λ> 0.29$~$μ$m) for rotational,…
Currently, the meteor shower part of Meteor Data Center database includes: 112 established showers, 563 in the working list, among them 36 have the pro tempore status. The list of shower complexes contains 25 groups, 3 have established status and 1 has the pro tempore status. In the past three years, new meteor showers submitted to the MDC database were detected amongst the meteors observed by CAMS stations (Cameras for Allsky Meteor Surveillance), those included in the EDMOND (European viDeo MeteOr Network Database), those collected by the Japanese SonotaCo Network, recorded in the IMO (Inter…
A variationally computed $^{28}$SiH$_4$ rotation-vibration line list applicable for temperatures up to $T=1200\,$K is presented. The line list, called OY2T, considers transitions with rotational excitation up to $J=42$ in the wavenumber range $0$--$5000\,$cm$^{-1}$ (wavelengths $λ> 2\,μ$m). Just under 62.7 billion transitions have been calculated between 6.1 million energy levels. Rovibrational calculations have utilized a new `spectroscopic' potential energy surface determined by empirical refinement to 1452 experimentally derived energy levels up to $J=6$, and a previously reported \textit{a…
New molecular line lists for calcium monohydride ($^{40}$Ca$^{1}$H) and magnesium monohydride ($^{24}$Mg$^{1}$H) and its minor isotopologues ($^{25}$Mg$^{1}$H and $^{26}$Mg$^{1}$H) are presented. The rotation-vibration-electronic (rovibronic) line lists, named \texttt{XAB}, consider transitions involving the \X, \A, and \BBp\ electronic states in the 0--30\,000~cm$^{-1}$ region (wavelengths $λ> 0.33$~$μ$m) and are suitable for temperatures up to 5000 K. A comprehensive analysis of the published spectroscopic literature on CaH and MgH is used to obtain new extensive datasets of accurate rovibro…
The Shower Database (SD) of the Meteor Data Center (MDC) has been operating for 15 years and is used by the entire community of meteor astronomers. It contains meteor showers categorised in individual lists on the basis of their status. Since the inception of the SD, no objective rules for moving showers between individual lists have been established. The content of the SD has not yet been checked for the correctness of the meteor data contained therein. Our aims are (1) to formulate criteria for nominating meteor showers for established status, (2) to improve the rules for the removal of show…
Stellar, substellar, and planetary atmosphere models are all highly sensitive to the input opacities. Generational differences between various state-of-the-art stellar/planetary models are primarily because of incomplete and outdated atomic/molecular line-lists. Here we present a database of pre-computed absorption cross-sections for all isotopologues of key atmospheric molecules relevant to late-type stellar, brown dwarf, and planetary atmospheres: MgH, AlH, CaH, TiH, CrH, FeH, SiO, TiO, VO, and H2O. The pressure and temperature ranges of the computed opacities are between 10$^{-6}$--3000~bar…
Comprehensive rotation-vibration line lists are presented for the two main isotopologues of methyl chloride, $^{12}$CH$_3{}^{35}$Cl and $^{12}$CH$_3{}^{37}$Cl. The line lists, OYT-35 and OYT-37, are suitable for temperatures up to $T=1200\,$K and consider transitions with rotational excitation up to $J=85$ in the wavenumber range $0$--$6400\,$cm$^{-1}$ (wavelengths $λ> 1.56\,μ$m). Over 166 billion transitions between 10.2 million energy levels have been calculated variationally for each line list using a new empirically refined potential energy surface, determined by refining to 739 experiment…
A new hot line list for $^{14}$NH$_3$ is presented. The line list CoYuTe was constructed using an accurate, empirically refined potential energy surface and a CCSD(T)/aug-cc-pVQZ ab initio dipole moment surface of ammonia, previously reported. The line list is an improvement of the ammonia line list BYTe [Yurchenko et al., Mon. Not. R. Astron. Soc., 413, 1828 (2011)]. The CoYuTe line list covers wavenumbers up to 20000 cm$^{-1}$, i.e. wavelengths beyond 0.5 $μ$m for temperatures up to 1500 K. Comparisons with the high temperature experimental data from the literature show excellent agrement fo…
This work describes the update of NO along with the incorporation of NO$_{2}$ and N$_{2}$O to the HITEMP database. Where appropriate, the HITRAN line lists for the same molecules have also been updated. This work brings the current number of molecules provided by HITEMP to seven. The initial line lists originating from \textit{ab initio} and semi-empirical methods for each molecule have been carefully validated against available observations and, where necessary, adjustments have been made to match observations. We anticipate this work will be applied to a variety of high-temperature environme…
Remote sensing experiments require high-accuracy, preferably sub-percent, line intensities and in response to this need we present computed room temperature line lists for six symmetric isotopologues of carbon dioxide: $^{13}$C$^{16}$O$_2$, $^{14}$C$^{16}$O$_2$, $^{12}$C$^{17}$O$_2$, $^{12}$C$^{18}$O$_2$, $^{13}$C$^{17}$O$_2$ and $^{13}$C$^{18}$O$_2$, covering the range 0-8000 \cm. Our calculation scheme is based on variational nuclear motion calculations and on a reliability analysis of the generated line intensities. Rotation-vibration wavefunctions and energy levels are computed using the D…
A rovibronic line list for the ground ($X$ $^3Σ^-$) and first excited ($a$ $^1Δ$) states of phosphinidene, $^{31}$PH, is computed. The line list is designed for studies of exoplanetary and cool stellar atmospheres with temperatures up to 4000 K. A combination of empirical and ab initio data are used to produce the line list: potential energy curves (PECs) are fitted using experimental transition frequencies; these transitions are reproduced with a root mean square error of 0.01 cm$^{-1}$. The nuclear Schrödinger is solved using these PECs plus Born-Oppenheimer and spin splitting correction ter…
Line lists for the ground electronic ground state for six major isotopologues of nitric oxide are presented. The line lists are constructed using empirical energy levels (and line positions) and high-level {\it ab inito} intensities. The energy levels were obtained using a combination of two approaches, from an effective Hamiltonian and from solving the rovibronic Schrödinger equation variationally. The effective hamiltonian model was obtained through a fit to the experimental line positions of NO available in the literature for all six isotopologues using the programs SPFIT and SPCAT. The var…
The CDMS was founded 1998 to provide in its catalog section line lists of molecular species which may be observed in various astronomical sources using radio astronomy. The line lists contain transition frequencies with qualified accuracies, intensities, quantum numbers, as well as further auxilary information. They have been generated from critically evaluated experimental line lists, mostly from laboratory experiments, employing established Hamiltonian models. Seperate entries exist for different isotopic species and usually also for different vibrational states. As of December 2015, the num…
The ExoMol project is dedicated to providing molecular line lists for exoplanet and other hot atmospheres. The ExoMol procedure uses a mixture of ab initio calculations and available laboratory data. The actual line lists are generated using variational nuclear motion calculations. These line lists form the input for opacity models for cool stars and brown dwarfs as well as for radiative transport models involving exoplanets. This paper is a collection of molecular opacities for 52 molecules (130 isotopologues) at two reference temperatures, 300 K and 2000 K, using line lists from the ExoMol d…
A rotation-vibration line list for the electronic ground state ($\tilde{X}^{1}A_{1}$) of SiH$_2$ is presented. The line list, named CATS, is suitable for temperatures up to 2000 K and covers the wavenumber range 0 - 10,000 cm$^{-1}$(wavelengths $>1.0$ $μ$m) for states with rotational excitation up to $J=52$. Over 310 million transitions between 593 804 energy levels have been computed variationally with a new empirically refined potential energy surface, determined by refining to 75 empirical term values with $J\leq 5$ and a newly computed high-level ab initio dipole moment surface. This is th…
Silicon mononitride ($^{28}$Si$^{14}$N, $^{29}$Si$^{14}$N, $^{30}$Si$^{14}$N, $^{28}$Si$^{15}$N) line lists covering infrared, visible and ultraviolet regions are presented. The \name\ line lists produced by ExoMol include rovibronic transitions between six electronic states: \XS, \AS, \BS, \DS, \asi, \bsi. The \ai\ potential energy and coupling curves, computed at the multireference configuration interaction (MRCI/aug-cc-pVQZ) level of theory, are refined for the observed states by fitting their analytical representations to 1052 experimentally derived SiN energy levels determined from rovibr…
Computing and using opacities is a key part of modeling and interpreting data of exoplanetary atmospheres. Since the underlying spectroscopic line lists are constantly expanding and currently include up to ~ 10^10 - 10^11 transition lines, the opacity calculator codes need to become more powerful. Here we present major upgrades to the HELIOS-K GPU-accelerated opacity calculator and describe the necessary steps to process large line lists within a reasonable amount of time. Besides performance improvements, we include more capabilities and present a toolbox for handling different atomic and mol…
SiS has long been observed in the circumstellar medium of the carbon-rich star IRC+10216 CW Leo. Comprehensive and accurate rotation-vibrational line lists and partition functions are computed for 12 isotopologues of silicon sulphide ($^{28}$Si$^{32}$S, $^{28}$Si$^{34}$S, $^{29}$Si$^{32}$S, $^{28}$Si$^{33}$S, $^{30}$Si$^{32}$S, $^{29}$Si$^{34}$S, $^{30}$Si$^{34}$S, $^{28}$Si$^{36}$S, $^{29}$Si$^{33}$S, $^{29}$Si$^{36}$S, $^{30}$Si$^{33}$S, $^{30}$Si$^{36}$S) in its ground (X $^1Σ^+$) electronic state. The calculations employ an existing spectroscopically accurate potential energy curve (PEC) d…
A new hot line list for the main isotopologue of CO$_2$ is presented. The line list consists of almost 2.5 billion transitions between 3.5 million rotation-vibration states of CO$_2$ in its ground electronic state, covering the wavenumber range 0-20000 cm$^{-1}$ ($λ>0.5$ $μ$m) with the upper and lower energy thresholds of 36 000 cm$^{-1}$ and 16 000 cm$^{-1}$, respectively. The ro-vibrational energies and wavefunctions are computed variationally using the Ames-2 accurate empirical potential energy surface. The ro-vibrational transition probabilities in the form of Einstein coefficients are com…
Silicon dioxide (SiO$_2$) is expected to occur in the atmospheres of hot rocky super-Earth exoplanets but a lack of spectroscopic data is hampering its possible detection. Here, we present the first, comprehensive molecular line list for SiO$_2$. The line list, named OYT3, covers the wavenumber range 0\,--\,6000~cm$^{-1}$ (wavelengths $λ> 1.67$~$μ$m) and is suitable for temperatures up to $T=3000$~K. Almost 33 billion transitions involving 5.69 million rotation-vibration states with rotational excitation up to $J=255$ have been computed using robust first-principles methodologies. The OYT3 lin…
Potassium hydroxide (KOH) and sodium hydroxide (NaOH) are expected to occur in the atmospheres of hot rocky super-Earth exoplanets but a lack of spectroscopic data is hampering their potential detection. Using robust first-principles methodologies, comprehensive molecular line lists for KOH and NaOH that are applicable for temperatures up to $T=3500$ K are presented. The KOH OYT4 line list covers the 0-6000 cm$^{-1}$ (wavelengths $λ> 1.67$ $μ$m) range and comprises 38 billion transitions between 7.3 million energy levels with rotational excitation up to $J=255$. The NaOH OYT5 line list covers …
Context. In 2020, the initial version of the Stellar Potential Perturbers Database (StePPeD) was presented with the aim to deliver up-to-date information on the stars and stellar systems that may perturb a long-period comet motion. We used the minimal distance between a star and the Sun as a selecting tool when compiling a list of interesting objects with close encounters with the Solar System, and our selection for that study was based on Gaia DR2 data. Aims. When the Gaia EDR3 data release was published, it became necessary to update this database. Additionally, we performed Monte Carlo simu…
A new line list for AlH is produced. The WYLLoT line list spans two electronic states $X\,{}^1Σ^+$ and $A\,{}^1Π$. A diabatic model is used to model the shallow potential energy curve of the $A\,{}^1Π$ state, which has a strong pre-dissociative character with only two bound vibrational states. Both potential energy curves are empirical and were obtained by fitting to experimentally derived energies of the $X\,{}^1Σ^+$ and $A\,{}^1Π$ electronic states using the diatomic nuclear motion codes Level and Duo. High temperature line lists plus partition functions and lifetimes for three isotopologues…
A new line list for hydronium (H$_3$$^{16}$O$^+$) is computed. The line list is based on a new ab initio dipole moment surface (CCSD(T)/aug-cc-pVQZ) and a new empirical potential energy surface (PES). The empirical PES of H$_3$O$^+$ was obtained by refining an ab initio surface through a global fit to the experimentally determined ro-vibrational energies collected from the literature covering the ground, $ν_1^{\pm}$, $ν_2^{\pm}$, $2ν_2^{\pm}$, $ν_3^{\pm}$ and $ν_4^{\pm}$ vibrational states. The line list covers the wavenumber range up to 10 000 cm$^{-1}$ (wavelengths $>1 μ$m) and should be com…
A new line list for H$_2$$^{16}$O is presented. This line list, which is called POKAZATEL, includes transitions between rotation-vibrational energy levels up to 41000 cm$^{-1}$ in energy and is the most complete to date. The potential energy surface (PES) used for producing the line list was obtained by fitting a high-quality ab initio PES to experimental energy levels with energies of 41000 cm$^{-1}$ and for rotational excitations up to $J=5$. The final line list comprises all energy levels up to 41000 cm$^{-1}$ and rotational angular momentum $J$ up to 72. An accurate ab initio dipole moment…
A new ro-vibrational line list for the ground electronic state of the main isotopologue of acetylene, $^{12}$C$_2$H$_2$, is computed as part of the ExoMol project. The aCeTY line list covers the transition wavenumbers up to 10,000 cm$^{-1}$ ($ λ>1$ $μ$m), with lower and upper energy levels up to 12,000 cm$^{-1}$ and 22,000 cm$^{-1}$ considered, respectively. The calculations are performed up to a maximum value for the vibrational angular momentum, $K_{\rm max}=L_{\rm max}$ = 16, and maximum rotational angular momentum, $J$ = 99. Higher values of $J$ were not within the specified wavenumber win…
A computed line list for hydrogen peroxide, H$_2{}^{16}$O$_2$, applicable to temperatures up to $T=1250$~K is presented. A semi-empirical high accuracy potential energy surface is constructed and used with an {\it ab initio} dipole moment surface as input TROVE to compute 7.5 million rotational-vibrational states and around 20 billion transitions with associated Einstein-$A$ coefficients for rotational excitations up to $J=85$. The resulting APTY line list is complete for wavenumbers below 6~000 cm$^{-1}$ ($λ< 1.67$~$μ$m) and temperatures up to 1250~K. Room-temperature spectra are compared wit…
Line lists for magnesium oxide are computed and extensive comparisons are made with existing experimental spectra. The LiTY line lists cover all ro-vibration transitions within the five lowest-lying electronic states ($X\,{}^1Σ^+$, $a\,{}^3Π$, $A\,{}^1Π$, $B\,{}^1Σ^+$ and $b\,{}^3Σ^{+}$) and five isotopologues: $^{24}$Mg$^{16}$O, $^{25}$Mg$^{16}$O, $^{26}$Mg$^{16}$O, $^{24}$Mg$^{17}$O, $^{24}$Mg$^{18}$O, $^{24}$Mg$^{17}$O and $^{24}$Mg$^{18}$O. The calculation use potential energy cures, spin-orbit and electronic angular momentum couplings curves determined by fitting to empirical energy level…
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 $X$ $^{2}Π$ electronic state as well as transitions to the low-lying $A$ $^{2}Δ$ and $a$ $^{4}Σ^-$ 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 p…
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 $X$ ${}^2Π$ 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 produ…
Indications of aluminium monoxide in atmospheres of exoplanets are being reported. Studies using high-resolution spectroscopy should allow a strong detection but require high accuracy laboratory data. A \textsc{marvel} (measured active rotational-vibrational energy levels) analysis is performed for the available spectroscopic data on $^{27}$Al$^{16}$O: 22\,473 validated transitions are used to determine 6\,485 distinct energy levels. These empirical energy levels are used to provide an improved, spectroscopically accurate version of the ExoMol ATP line list for $^{27}$Al$^{16}$O; at the same t…
Comprehensive line lists for phosphorus monoxide ($^{31}$P$^{16}$O) and phosphorus monosulphide ($^{31}$P$^{32}$S) in their $X$ $^2Π$ 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 Schrödinger 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, $…
Accurate line lists for the carbon dimer, C$_2$, are presented. These line lists cover rovibronic transitions between the eight lowest electronic states: $X\,{}^{1}Σ_{g}^{+}$, $a\,{}^{3}Π_{u}$, $A\,{}^{1}Π_{u}$, $b\,^{3}Σ_{g}^{-}$, $b\,^{3}Σ_{g}^{-}$, $c\,^{3}Σ_{u}^{+}$, $d\,{}^{3}Π_{g}$, $B\,{}^{1}Δ_{g}$, $B^\prime\,{}^{1}Σ_{g}^{+}$. Potential energy curves (PECs) and transition dipole moment curves are computed on a large grid of geometries using the aug-cc-pwCVQZ-DK/MRCI level of theory including core and core-valence correlations and scalar relativistic energy corrections. The same level o…
A publicly available database of opacities for molecules of astrophysical interest, ExoMolOP, has been compiled for over 80 species, based on the latest line list data from the ExoMol, HITEMP and MoLLIST databases. These data are generally suitable for characterising high temperature exoplanet or cool stellar/substellar atmospheres, and have been computed at a variety of pressures and temperatures, with a few molecules included at room-temperature only from the HITRAN database. The data are formatted in different ways for four different exoplanet atmosphere retrieval codes; ARCiS, TauREx, NEME…
We present the first variational calculation of a hot temperature ab initio line list for the CH$_3$ radical. It is based on a high level ab initio potential energy surface and dipole moment surface of CH$_3$ in the ground electronic state. The ro-vibrational energy levels and Einstein $A$ coefficients were calculated using the general-molecule variational approach implemented in the computer program TROVE. Vibrational energies and vibrational intensities are found to be in very good agreement with the available experimental data. The line list comprises 9,127,123 ro-vibrational states ($J\le …
Calculations are reported on the rotation-vibration energy levels of the arsine molecule with associated transition intensities. A potential energy surface (PES) obtained from \textit{ab initio} electronic structure calculations is refined to experimental data, and the resulting energy levels display sub-wavenumber accuracy for all reliably known $J=0$ term values under 6500 cm$^{-1}$. After a small empirical adjustment of the band centres, our calculated ($J=1-6$) rovibrational states reproduce 578 experimentally derived energies with a root-mean-square error of 0.122 cm$^{-1}$. Absolute line…
