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Massive stars disrupt their natal molecular cloud material through radiative and mechanical feedback processes. These processes have profound effects on the evolution of interstellar matter in our Galaxy and throughout the universe, from the era of vigorous star formation at redshifts of 1–3 to the present day. The dominant feedback processes can be probed by observations of the Photo-Dissociation Regions (PDRs) where the far-ultraviolet photons of massive stars create warm regions of gas and dust in the neutral atomic and molecular gas. PDR emission provides a unique tool to study in detail the physical and chemical processes that are relevant for most of the mass in inter- and circumstellar media including diffuse clouds, proto-planetary disks, and molecular cloud surfaces, globules, planetary nebulae, and star-forming regions. PDR emission dominates the infrared (IR) spectra of star-forming galaxies. Most of the Galactic and extragalactic observations obtained with the James Webb Space Telescope (JWST) will therefore arise in PDR emission. In this paper we present an Early Release Science program using the MIRI, NIRSpec, and NIRCam instruments dedicated to the observations of an emblematic and nearby PDR: the Orion Bar. These early JWST observations will provide template data sets designed to identify key PDR characteristics in JWST observations. These data will serve to benchmark PDR models and extend them into the JWST era. We also present the Science-Enabling products that we will provide to the community. These template data sets and Science-Enabling products will guide the preparation of future proposals on star-forming regions in our Galaxy and beyond and will facilitate data analysis and interpretation of forthcoming JWST observations.

We have studied the profile of the 2140 cm−1fundamental band of solid carbon monoxide CO at low temperature 10–15 K by infrared transmission spectroscopy and by reflection absorption infrared RAIR spectroscopy. In particular, transmission spectra have been taken after CO had been adsorbed on a bare crystalline silicon substrate and on pre-adsorbed solid N2layers of different thickness. RAIR spectra have been taken after CO had been adsorbed on a bare gold substrate and on pre-adsorbed solid N2layers of different thickness. Laboratory spectra show that the profile of the fundamental CO band at about 2140 cm−1is different in the different instances considered. In particular, we have found that the relative intensity of the LO and TO modes of the CO band depends on the thickness of the N2layer. Here we present the experimental results and show that these can be predicted by the elementary electromagnetic theory.

A large variety of carbon rich macromolecules has been studied in our laboratory, before, during, and after ion irradiation (3‐60 keV ions), by in situIR and Raman spectroscopies. In this paper we present results obtained on: (a) Films of frozen H2O:CH4:N2mixtures that have been deposited at low temperature (12 K) on a silicon substrate, and irradiated with fast ions. Irradiation causes the formation of organic refractory residues whose spectra have been recorded and studied also after further irradiation at room temperature. (b) Pentacene (a Polyciclic Aromatic Hydrocarbon, PAH) whose Raman spectra have been studied also during ion irradiation at room temperature. (c) Thin samples of fullerene (C60) films also irradiated at room temperature.

Silicates are one of the principal components present in Solar System objects.Silicates evolve in space modifying their physical properties according to theastronomical environments they go through. To characterise the nature of TNOsin the framework of the formation and evolution of the Solar System, experimentson structural transitions of silicates have been performed in the laboratoryto simulate some of the processing suffered by the dust. The infrared spectralproperties of possible silicate candidates thought to be present in TNOs have beenstudied. The results of thermal annealing of amorphous silicates and amorphisationof crystalline forsterite (pure-Mg olivine) by ion irradiation are presented. Theobservable properties of TNOs surfaces are inferred.

Compact pressure effects on Sb-doped tetragonal zirconia have been monitored using XRD, Raman and FTIR spectroscopies. A martensitic tetragonal→monoclinic transformation, driven by compact pressure, has been observed upon pelletisation of stabilised samples. By contrast, no monoclinic phase has been observed on amorphous powders upon pelletisation and firing. Sb surface segregation has been observed upon firing of pellets. The phenomenon has been quantitised by angle resolved XPS using the recent Gries algorithms to evaluate the Zr 3d photoelectron inelastic mean free path in ZrO2 which, in turn, compares well with previous experimental data. Surface Sb segregation occurs over a depth range and involves many ionic planes. An experimental estimate of the Sb segregation enthalpy has been evaluated.