JWST allows us to characterise the properties of gas and dust in the inner regions of protoplanetary disks with unprecedented sensitivity and spectral resolution. These planet-forming disks are dynamic objects. Solids grow in size and drift inward, potentially enriching the gas of the inner disk in volatile molecules transported from the outer disk as ices. Concurrently, the formation of substructures such as rings and vortices may prevent this material from being delivered to the inner disk, changing the chemical composition of the material available to forming planets. JWST spectra show emission from H₂O, CO₂, hydrocarbons, and multiple as yet unidentified species. Here, I present the first results from the MINDS (MIRI mid-IR Disk Survey, PI: Th. Henning) program, which has observed multiple disks around brown dwarf and T-Tauri stars. Observations include the first detections of benzene and ¹³CO₂ in protoplanetary disks and a range of derived gas-phase carbon to oxygen ratios. These data allow us to make preliminary connections between the composition of the inner disk and that of the outer disk.

VY CMa is a supermassive, late-type, oxygen-rich star surrounded by a dense envelope of dust and molecules. Radio observations have identified about 25 different molecular species (plus many isotopologues) in the vicinity of this star, but little is known about molecular features in the mid-IR wavelength range. In a recent (and ongoing) line survey, we investigated the region around 7 to 8 and 10 μm with the TEXES instrument at IRTF (Mauna Kea, Hawai'i) and the EXES spectrograph aboard the SOFIA airborne telescope. Both instruments are high-resolution instruments with R=100,000. Preliminary results on the observed NH₃ and SiO spectra will be presented. Other observed spectral features will be discussed. With the decommissioning of SOFIA in September 2022, a high-resolution mid-IR telescope will no longer be available for frequency ranges blocked by the Earth's atmosphere. However, for some applications, the space telescope JWST can be a very valuable tool for studying the envelope of VY CMa, even though it has only a resolution of R=3000. Possible synergies with the current mid-IR line survey and JWST will be discussed.

The near infrared region of the spectrum is useful for applications such as the JWST Near Infrared Spectrograph, but assigning peaks in that region can be challenging and could benefit from additional experimental validation. HD-2DIR is a new technique that is being developed to decongest rovibrational spectra and to experimentally assign peaks in the near infrared region using previously assigned peaks in the mid-infrared region.

Historical sketch: Charlie Townes and I are the only two astronomical spectroscopists who switched to infrared after few years of radio astronomy. Townes did atomic spectroscopy and discovered the black hole at the center of the Galaxy.Wollman, E.R., Geballe, T.R., Lacy, J.H., Townes, C.H. 1976, ApJ 205, L5; 1977, ApJ 218, L103 switched because H₃⁺, central in astrochemistry, has spectrum only in the infrared region. Dense and diffuse clouds: It took us 16 years to observe the spectrum of H₃⁺ in dense cloudsGeballe, T.R., Oka, T. 1996 Nature, 384, 334s theoretically predicted by Herbst and Klemperer and Watson, but had we tried diffuse clouds in the Galactic center we would have had found it withing a few years. Radio (ALMA) astronomy is for emission spectroscopy in dense clouds while infrared (JWST) spectroscopy is for absorption spectroscopy in diffuse clouds. Molecules of interest: So far astrochemistry has been mostly the science of dense clouds, but JWST will bring in rich chemistry in diffuse clouds. Dense clouds are localized. Diffuse clouds give a bigger picture. Patrick Thaddeus said, “One should not look at an elephant with a magnifying glass”. Spectra of the following molecules will be observed: HD, CH, NH, OH, HD⁺, CH⁺, NH⁺, OH⁺, H₃⁺, H₂D⁺, CH₂, NH₂, H₂O, CH₂⁺, NH₂⁺, H₂O⁺. These are kind of molecules observed by Herschel Observatory. Many of them were analyzed as in dense clouds, but they are all in diffuse clouds. Apart from H₃⁺ they are all polar molecules with high rotational constants therefore the spectrum is composed of 1 line apart from fine and hyperfine structure. For H₃⁺ three rotational levels (J,K) = (1,1), (1,0), and (3,3) levels are populated. Stars of interest: Absorption spectroscopy needs bright and young stars with a smooth continuum for the radiation source. Ben McCall found 27 stars that are usable to conduct absorption spectroscopy toward the Galactic disk.Indriolo, N., McCall, B.J. 2012, ApJ 745, 91e found 18 stars toward the Galactic centerOka, T., Geballe, T., Goto, M., Usuda, T., McCall, B.J., Indriolo, N. 2019, ApJ 883, 54(31pp)hese stars will be useful for the JWST observation.

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Footnotes:

Wollman, E.R., Geballe, T.R., Lacy, J.H., Townes, C.H. 1976, ApJ 205, L5; 1977, ApJ 218, L103I Geballe, T.R., Oka, T. 1996 Nature, 384, 334a Indriolo, N., McCall, B.J. 2012, ApJ 745, 91W Oka, T., Geballe, T., Goto, M., Usuda, T., McCall, B.J., Indriolo, N. 2019, ApJ 883, 54(31pp)T

C₃, a pure carbon chain molecule that has been identified in different astronomical environments, is considered a good probe of kinetic temperatures through observation of transitions involving its low-lying bending mode (ν₂) in its ground electronic state. With the aim to investigate this bending mode with multiple quanta of excitation, we have undertaken high resolution optical and mid-infrared investigations on the species produced in discharge experiments. We report here the most complete analysis of the \TildeX and \TildeA states of C₃ (literature and present study) using a single PGOPHER file. New experimental measurements, reported in the past years at ISMS, result in 36 rovibronic \TildeA ¹Π_u− \TildeX ¹Σ_g⁺ bands (originating from \TildeX(0v₂0), v₂ = 0−5, levels) recorded by laser induced fluorescence spectroscopy at the University of Science and Technology of China and the rovibrational ν₃ band (revealing hot bands involving up to 5 quanta of excitation in ν₂) recorded by Fourier-transform infrared spectroscopy using a globar source on the AILES beamline of the SOLEIL synchrotron facility. The combined fit allows for the accurate determination of the rotational parameters and absolute energy levels of C₃, in particular for states involving the bending mode. The spectroscopic information derived from this work enables new interstellar searches for C₃, not only in the infrared and optical regions investigated here but also notably in the ν₂ band region (around 63 cm⁻¹) where vibrational satellites can now be accurately predicted. This makes C₃ a universal diagnostic tool to study very different astronomical environments, from dark and dense to translucent clouds.

The methyl cation (CH₃⁺), one of the simplest cations, is postulated to play a pivotal role in the chemistry of interstellar and circumstellar environments, but remains so far elusive outside the Solar System. We report the detection of a series of infrared lines in a protoplanetary disk in Orion using the JWST, which we attribute to CH₃⁺. The presence of CH₃⁺ results from the hot UV-driven chemistry, initiated at the surface of the disk by the nearby massive stars of the Trapezium cluster. The detection of this species, which is at the root of carbon chemistry in space, opens the possibility to study yet unexplored pathways of hot gas-phase organic chemistry at play in planet forming disks and beyond.

A large number of astrophysically relevant molecules can be clearly identified by characteristic spectra in the mid-infrared range. Among them are important species such as CO₂ or C₃, which cannot be detected in the microwave range due to the lack of a permanent dipole moment. The broad spectral coverage of the MIRI spectrometer aboard JWST allows detection of a large number of molecules in the envelopes of aging stars. Together with observations in the microwave and optical spectral regions, the infrared region provides valuable information about the physical and chemical processes in the gas surrounding these stars. While infrared observations with Earth-based telescopes such as the IRTF on Mauna Kea / Hawaii are limited due to infrared absorption in the Earth's atmosphere, JWST will provide an unrestricted view over the entire spectral range from 5 - 28 μm. The spectral resolution of JWST (R = 2000 - 3000) is sufficient to detect rotational vibrational transitions of small diatomic to triatomic molecules as well as characteristic vibrational bands of larger molecules. A large number of new molecules are expected to be discovered in the infrared spectra of late-type stars, provided their spectral signatures are known from precise laboratory studies. The laboratory astrophysics group in Kassel is conducting experiments in the 3-12 μm range with quantum cascade lasers and OPO lasers. In combination with electric discharge sources and laser ablation, a variety of molecules such as Si₂C [1], C₃, TiO [2], Al₂O and VO can be produced in cold supersonic jets, which are studied with high resolution infrared spectroscopy. The talk will give a brief insight into the ongoing work.
[1] D. Witsch, V. Lutter, A.A. Breier, K.M.T. Yamada, G.W. Fuchs, J. Gauss, T.F. Giesen, JPC A, 123, 4168 (2019). [2] D. Witsch, A.A. Breier, E. Döring, K.M.T. Yamada, T.F. Giesen, G.W. Fuchs JMS, 377, 111439 (2021).

Many complex organic molecules (iCOMs) ranging from diatoms to molecules containing up to 70 atoms, including formaldehyde, protonated formaldehyde, and glycolaldehydeL.E. Snyder, D. Buhl, B. Zuckerman, P. Palmer, Phys. Rev. Lett. 22 (1969) 679–681.; M. Ohishi, S.I. Ishikawa, T. Amano, H. Oka, W.M. Irvine, J.E. Dickens, L.M. Ziurys, A.J. Apponi, Astrophys. J. 471 (1996) L61–L64.; J.M. Hollis, F.J. Lovas, P.R. Jewell, Astrophys. J. 540 (2000) L107–L110.ave been detected in space using astronomical observations. To understand the synthetic pathways of such potential prebiotic species in space, it is crucial to investigate their formation in the laboratory. In this work, we present results relevant to the synthesis of the simplest “sugar”, glycolaldehyde, using a cryogenic 22-pole ion trap stationed at the infrared free-electron laser laboratory FELIX.D.B. Rap, J.G.M. Schrauwen, A.N. Marimuthu, B. Redlich, S. Brünken, Nat. Astron. 6 (2022) 1059–1067.e investigate the ion-neutral gas-phase formation of (protonated) glycolaldehyde starting from neutral formaldehyde and its cationic forms, [H₂CO]⁺ and [H₃CO]⁺. Gas-phase vibrational spectra of the reactant [H₃CO]⁺ and the mass-spectroscopically identified products [H₅C₂O]⁺ and [H₅C₂O₂]⁺ were recorded using cryogenic IR action spectroscopy in the frequency range 650-1900 cm⁻¹, and are compared to results of quantum chemical calculations for structural characterization between different isomers. First insights into potential reaction pathways will be presented based on this combined approach, and they will be complemented with a Markov state model of the reaction mechanisms based on molecular dynamics simulationsW. Wang, X. Liu, J. Pérez-Ríos, J. Phys. Chem. A. 125 (2021) 5670–5680.^, X. Liu, W. Wang, S.C. Wright, M. Doppelbauer, G. Meijer, S. Truppe, J. Pérez-Ríos, J. Chem. Phys. 157 (2022) 074305.t

Apart of being the most abundant metal in earth and the well-known leading role in the field of organic prosthetic group of proteins, iron potentially represents a crucial element for understanding interstellar processes, the evolution of interstellar dust and interstellar medium (ISM) composition. Despite the presumable gas-phase presence of iron in the ISM due to its very high abundance in the galaxy, its difficult detection in the interstellar gas-phase to date may be due to depletion of iron hidden in interstellar dust. Nevertheless, although ISM observations show iron to be severely depleted, it is highly expected to find iron-containing gas-phase molecular species in the ISM. This idea is reinforced by detection of FeCN in the ISML.N. Zack, D.T. Halfen and L.M. Ziurys, Astrophys. J. Lett., 2011, 733(2), L36r observed evidence of FeO presence in interstellar molecular clouds.C.M. Walmsley, R. Bachiller, G.P. Des Forêts and P. Schilke, Astrophys. J., 2002, 566(2), L109-L112as-phase iron dihydrogen clusters and their deuterium substitutes were formed and stored in a cooled cell (ca. 80K) of a 4.7 T Fourier-Transform Ion Cyclotron Resonance instrument. Infrared photodissociation spectra were recorded in the H–H and D–D stretch region of 2230–4000 cm–1, supported by quantum chemical calculations. The spectral signature of the infrared photon absorption was reflected in the dissociation of intact H₂ or D₂ molecule. Additionally, to provide spectroscopic data on FeH⁺ and complete previous analysis of Ar₂FeH⁺,S. Jin, J. Heller, C. van der Linde, M. Ončák and M.K. Beyer, J Phys Chem Lett, 2022, 13(25), 5867e investigated overtone bands of Ar₂FeH⁺ and ArFeH⁺ in the 2300–4000 cm–1 region. We observed that while ArFeH⁺ exhibits only a Fe–H overtone vibration in this region other plausible electronic transitions appear for Ar₂FeH⁺, correlated with the ⁵D state of the iron atom. Ion FT-IR spectroscopy combined with mass spectrometry represent a proven high-resolution tool to determine the molecular composition and structural behavior. Furthermore, overtone bands recognition may be used as a valuable strategy to obtain unambiguous identification of polyatomic aggregates fingerprints and further understanding of ISM composition and reactivity.

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Footnotes:

L.N. Zack, D.T. Halfen and L.M. Ziurys, Astrophys. J. Lett., 2011, 733(2), L36o C.M. Walmsley, R. Bachiller, G.P. Des Forêts and P. Schilke, Astrophys. J., 2002, 566(2), L109-L112G S. Jin, J. Heller, C. van der Linde, M. Ončák and M.K. Beyer, J Phys Chem Lett, 2022, 13(25), 5867w