About 75% of observing time with JWST is used for spectroscopy. With its versatile infrared spectroscopic instrumentation, JWST is powerful tool for enabling new understanding of the universe. From the Solar System and exoplanets, over star- and planet formation, and to the distant Universe, JWST is already revealing new aspects of our molecular universe, and at the same time posing intriguing new questions. We are seeing new detections of molecules in exoplanetary atmospheres from sensitive transit spectroscopy, revealing complex organic molecules in prestellar ices, and opening a new window on bulk volatile chemistry in protoplanetary disks. I will provide an overview of the status of the JWST mission, and in particular discuss how JWST spectroscopy is becoming a driving force in astrochemistry and beyond. I will present highlights from key JWST observing programs, including new observations of protostellar and protoplanetary chemistry, and look ahead to the next year of infrared spectroscopy from space.

The HITRAN and HITEMP molecular spectroscopic databases are critical for interpreting and modeling planetary spectra, including those of moons and exoplanets. With the launch of JWST, we have a unique opportunity to observe exoplanetary atmospheres that are very diverse in temperature, pressure, and composition. However, to fully utilize this opportunity, we need to ensure that the spectroscopic databases are up for the challenge.
To this end, the HITRAN2020 edition has made significant improvements to enhance the scientific output of the JWST mission. For example, broadening parameters due to the ambient pressure of He-, H₂-, CO₂, and H₂O gases have been added for many HITRAN molecules. This addition is crucial since hydrogen and helium are the primary constituents in the atmospheres of gas giants, while carbon dioxide and water vapor dominate the atmospheres of many rocky planets. Furthermore, spectral and dynamic ranges for many relevant molecules have been extended, and new isotopologues have been added. Additionally, six new molecules have been included bringing the total to 55. There are also experimental cross-sections for over 300 molecules for which no reliable quantum mechanical models exist yet. Another significant improvement is the substantial update that has been made to the database of collision-induced absorption.
This presentation will highlight the state-of-the-art data available in HITRAN, as well as the significant updates that HITEMP is currently undergoing. We will also discuss the next steps and data demands required to continue advancing our understanding of planetary atmospheres.

With a new generation of observatories coming online this decade, the process of characterizing exoplanet atmospheres will need to be reinvented. Currently mostly on the instrumental side, characterization bottlenecks will soon stand by the models used to translate spectra into atmospheric properties. Limitations stemming from our stellar and atmospheric models have already been highlighted. Here, we show that the current limitations of the opacity models used to decode exoplanet spectra propagate into an accuracy wall at  ∼ 0.5-1.0 dex (i.e., 3 to 10×) on the atmospheric properties, which is an order of magnitude above the precision targeted by some JWST Cycle 1 programs and needed for, e.g., meaningful C/O-ratio constraints and biosignatures identification. We perform a sensitivity analysis using nine different opacity models and find that most of the retrievals produce harmonious fits owing to compensations in the form of > 5σ biases on the derived atmospheric parameters translating in the aforementioned accuracy wall. We suggest a two-tier approach to alleviate this problem involving a new retrieval procedure and guided improvements in opacity data, their standardization and optimal dissemination.

    Accurate knowledge of the absorption fingerprint of the species expected in the atmospheres of the hot Jupiter exoplanets is required to allow their detection. MethaneM. R. Swain, G. Vasisht, G. Tinetti, Nature, 463 (7281), 637-639 (2008)nd acetyleneP. Giacobbe, et al., Nature, 592 (7853), 205-208 (2021)ere already detected in such environments, and the presence of other small hydrocarbons such as ethylene (C₂H₄) is expected. However, spectral assignment of C₂H₄ transitions is not available at wavenumbers higher than 3500 cm⁻¹, partly due to its highly congested absorption spectrum at room temperature. To provide accurate assignments of the cold transitions, we perform cavity ring-down spectroscopy of a jet-cooled ethylene gas sample in the 1.6-1.7 μm spectral range. The gas contained in a high pressure reservoir is expanded into a low-pressure chamber through an 8.5cm-long slit with a tunable opening width ranging from 0 to 350 μm. This process induces a simplification of the absorption spectrum by reducing drastically the rotational temperature and by narrowing the absorption line widths. Three spectra were recorded with a vibrational temperature of about 220K but different rotational temperatures: 5K, 35K and 75K. Unambiguous assignment of the observed lines is performed using the TheoReTS ab initio line listM. Rey, A. V. Nikitin, Y. L. Babikov, and V. G. Tyuterev, J. Mol. Spectrosc., 327, 138–158 (2016)nd the temperature dependence of the transition intensities.

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Footnotes:

M. R. Swain, G. Vasisht, G. Tinetti, Nature, 463 (7281), 637-639 (2008)a P. Giacobbe, et al., Nature, 592 (7853), 205-208 (2021)w M. Rey, A. V. Nikitin, Y. L. Babikov, and V. G. Tyuterev, J. Mol. Spectrosc., 327, 138–158 (2016)a

In preparation for the upcoming observing facilities that will observe exoplanets, such as the ELT, ARIEL, and VLTI/ GRAVITY+ and the recently launched JWST, laboratory work is necessary. These facilities will provide an unprecedented sample of spectra of exoplanetary atmospheres and will, therefore, build a ‘standard model’ of how a planet’s chemistry depends on its star and the condition of its birth. Laboratory data on stable molecules that compose exoplanetary atmospheres, however, are far from complete, especially at high temperatures. The impact of dominant gases on the trace species is also rather unknown, thereby making the determination of molecular abundances difficult. Infrared laboratory spectra will therefore be critical to interpret the upcoming data on exoplanetary atmospheres. We use high resolution laboratory infrared spectroscopy to determine the effect of broadening and frequency shifts induced on N₂O from H₂ and He, and from temperature. This work will contribute to the growing database of spectral catalogues available to astronomers for the accurate characterisation of exoplanetary atmospheres.

Butene (C₄H₈) is one of many C₄-hydrocarbons predicted to be up to 10 ppb in Titan’s atmosphere by photochemical models, but yet to be detected most likely due to lack of reliable high-resolution spectroscopy, particularly at cold temperatures. As a continued work on high-resolution spectroscopy of trans-2-Butene (trans-2-C₄H₈: CH₃-CH=CH-CH₃), we present the pseudoline generation made from the same spectrum data sets in the 7 - 15 μm region (See F09 in the ISMS 2022). In total, 28 pure and N₂-mixture spectra were obtained at temperatures between 180 – 297 K using a Fourier transform spectrometer (Bruker IFS-125HR). All the spectra were fit together to derive a single set of pseudoline parameters, which includes line intensity and lower-state energy value at individual frequency bins that are considered as pseudoline positions. The pseudolines are found to reproduce the observed spectra via line-by-line radiative transfer calculations to within a few % across the spectral region. We have the pseudoline list compiled in a HITRAN database format to facilitate their implementation into existing radiative transfer codes, which use the HITRAN database for other molecules. We will present and discuss the results and performance of the pseudolines. It is anticipated that the results from this work will provide critical laboratory input toward a search for trans-2-Butene in Titan stratosphere that may be captured in the Cassini/CIRS spectra, or in future space-based (MIRI/JWST) and ground-based observations (e.g., TEXES/IRTF).Government support acknowledged.html:<hr /><h3>Footnotes: Government support acknowledged.

Accurate IR line lists of astronomically important molecules can help their quantitative analysis and modeling in planetary and exoplanetary atmosphere studies. To minimize the uncertainty of analysis resulting from IR line list or opacity data, the intensity prediction accuracy of semi-empirically computed IR line lists may be improved by using more accurately refined potential energy surface (PES) and more accurate ab initio dipole moment surface (DMS). Recently we reported Ames-1 296K IR line list for N₂O and its isotopologues, based on a PES refinement with σ_rms = 0.02 cm⁻¹for selected HITRAN2020 levels and band origins, and a DMS fitted from extrapolated CCSD(T)/aug-cc-pV(T,Q,5)Z dipoles in the range of 0 - 20,000 cm⁻¹, with fitting σ_rms = 2.7×10⁻⁵ a.u.. It has overall good agreement with published experimental data and effective dipole models, plus more reliable predictions for minor isotopologues. However, relatively larger discrepancies and extra sensitivities have been noticed on several bands, calling for further studies to verify and improve the accuracy of Ames intensity predictions. This investigation focuses on the dipole surface. A new CCSD(T) DMS series are fitted from various dipole sets computed on 8000 - 13,000 geometries with E_max = 10,000 - 17,000 cm⁻¹. With fitting σ_rms in the range of 10⁻⁵ - 10⁻⁷ a.u., we are able to track the DMS impact on IR intensities for each individual band or transition. Results and findings will be presented, e.g., the DMS sensitive predictions for bands like 1113←0000, and the stable predictions for other bands like ν₁←ν₂. The differences among the best performing DMS candidates increases beyond 10,000 cm⁻¹. It probably requires new experimental studies to consolidate a choice of Ämes-2" DMS and line lists. Other potential factors behind the intensity accuracy and uncertainties will also be discussed.

Aminoacetonitrile is an interstellar molecule with a prominent prebiotic role, already detected in the chemically-rich molecular cloud Sagittarius B2(N) and postulated to be present in the atmosphere of the largest Saturn's moon, Titan. To further support its observation in such remote environments and laboratory experiments aimed at improving our understanding of interstellar chemistry, we report a thorough spectroscopic characterization of aminoacetonitrile. Fundamental bands as well as spectroscopic and molecular parameters have been accurately computed by exploiting a composite scheme rooted in the coupled-cluster theory that accounts for the extrapolation to the complete basis set limit and core-correlation effects. From the experimental side, we report the analysis of the three strongest fundamental bands of aminoacetonitrile observed between 500 and 1000 cm⁻¹ in high-resolution infrared spectra. More generally, all computed band positions are in excellent agreement with the present and previous experiments. The only exception is the ν₁₅ band, for which we provide a revision of the experimental assignment, now in good agreement with theory.

In support of planetary atmosphere remote sensing and exobiology, we studied spectroscopy of phosphine (PH₃) in the full Tetradecad range, involving 26 rotationally resolved bands, for the first time. For this, we analyzed high-resolution FT-IR spectra in the 3769 - 4763 cm⁻¹region recorded at temperatures 200 K and 296 K. Overall 3242 line positions were assigned and modeled by using a combined theoretical model based on ab   initio calculations. The total nuclear motion Hamiltonian, including ab   initio Potential Energy Surface (PES), was reduced to an effective Hamiltonian using the high-order contact transformation method adapted to vibrational polyads of the AB₃ symmetric top molecules, followed by empirical optimization of the parameters. At this step, the measured line positions could be reproduced with a standard deviation of 0.0026 cm⁻¹, providing unambiguous identification for the observed features. We also obtained the effective dipole transition moments of the bands by fitting to the intensities from variational calculations using the ab   initio Dipole Moment Surface (DMS). The assigned lines were used to additionally determine 1609 vibration-rotational levels up to Jmax = 18 with their energy in the range of 3896-6037 cm⁻¹. Transitions for all 26 sublevels of the Tetradecad were identified but with noticeably a fewer number of transitions for fourfold excited bands due to their weaker intensity. We present the latest results and comparison with existing experimental spectra in the discussion of their validation and applications toward planetary atmosphere characterization.

We have developed a mid-infrared Doppler-free saturation absorption spectroscopy apparatus using a continuous-wave optical parametric oscillator (CW-OPO). Here we report a comprehensive spectral scan of the Q branch transitions of the ν₃=1 band of methane (CH₄) with an average linewidth (FWHM) of 4.5 MHz. The absolute frequency calibration was achieved using previously reported transition frequencies determined using optical frequency combs, while an etalon was used for relative frequency calibration. We report 12 transitions with improved accuracies of  3 MHz. These measurements are then used to lock to a single transition, which then can be used to access the higher polyads with a second photon via a transition that is measured through CW-CRDS.

An extensive analysis of the available spectroscopic data on methane is being performed. The MARVEL (Measured Active Rotational-Vibrational Energy Levels) algorithm by Furtenbacher et al is used to provide accurate empirical rovibrational energy levels for methane. Experimental data are collected from 159 sources; these are evaluated and then added to a database of measured transitions with their experimental uncertainties. Each transition must have assigned quantum numbers for their upper and lower states and an uncertainty. The database is being built starting from lower and moving towards higher polyads and used as an input for MARVEL. The self-consistency of the input transitions is evaluated during the MARVEL procedure, and the uncertainties are adjusted accordingly until a self-consistent network of energy levels is achieved. As part of this process, a constant cleansing of the database of incorrect and wrongly assigned transitions is performed. The output of the procedure is a set of empirical energy levels with their respective uncertainties, derived from the inversion of the input measured lines which will be used to update our calculated line lists. At the same time, the resulting energy levels will be used for the attribution of quantum numbers to unassigned experimental transitions.