Star and planet formation is one of the most fundamental structure-formation processes in the Universe. Physical processes of star and planet formation have widely been investigated as one of the major targets of observational astronomy and astrophysics during the last few decades. Meanwhile, star and planet formation is inevitably accompanied with the evolution of interstellar matter. Increasing observational sensitivity allows us to identify about 200 interstellar molecules so far. This indicates high chemical complexity of interstellar clouds and star-forming regions despite their extreme physical condition of low temperature (10-100 K) and low density (10²-10⁷ cm⁻³). Such chemical complexity would ultimately be related to an origin of a huge variety of substances in the Solar System. Thus, both physical and chemical approaches are indispensable to bridge star/planet formation studies and the Solar System science. In the last two decades, it is clearly demonstrated that envelopes and disks around solar-type protostars have significant chemical diversity: some sources harbor various saturated-"complex"-organic molecules (COMs) such as HCOOCH₃ and (CH₃)₂O, whereas some others harbor unsaturated species instead. The chemical diversity would originate from different duration time of the starless core phase of each protostar. In fact, sources showing intermediate-type of chemistry have also been found. On the other hand, the most interesting issue to be studied is how the chemical diversity in the protostellar envelopes/disks is brought into the later stages toward protoplanetary disks. Fortunately, such studies are now feasible with high sensitivity and angular-resolution capabilities of ALMA (Atacama Large Millimeter/Submillimeter Array). During its 7 year/cycle operation, spectacular images are being obtained after another by ALMA. These results have newly reminded us of a lack of sufficient information on molecular properties, such as accurate rest frequencies of molecular lines, desorption mechanism of molecules, isotopic fractionations of molecules, and so on. Modern importance of molecular science in relation to astronomy will be discussed by introducing recent observations with ALMA.

The surfaces of astronomical dust grains are a crucial site for chemical reactions. Observations of polarized emission from dust grains provide a powerful tool for investigating the sizes and distribution of dust grains in protoplanetary disks. We present ALMA observations of three protostellar disks at 3 mm and 870 μm: Haro 6-13, RY Tau, and MWC 480. At 870 μm, all three disks show polarization morphologies consistent with those produced by self-scattering. At 3 mm, Haro 6-13 shows a polarization morphology that may indicate radiative or mechanical alignment of grains, while RY Tau and MWC 480 still show polarization patterns that are consistent with scattering. Additionally, we present models of the polarization patterns different polarization mechanisms would be expected to produce in these disks.

This work aims to reveal new information about the gas and ice compositions of early star-forming regions and planetary/cometary atmospheres. To shed light on this topic, a new approach for analyzing the desorbed products of laboratory ices is being developed. The technique consists of the submillimeter spectroscopic analysis of thermally and photo-processed ices. This is the same spectroscopic technique used to remotely probe gas-phase compositions of interstellar space and planetary/cometary atmospheres. Therefore, the laboratory spectroscopic data provided are directly comparable to spectra collected via ground- and space-based telescopes. Furthermore, this technique is capable of distinguishing branching ratios of desorbed isomers, something that traditional laboratory ice studies have always struggled with. Experimental design and new results will be discussed.

In the course of the investigation of the rotational spectrum of prebiotic hydantoic acid by Fourier transform microwave spectroscopy coupled to a laser ablation source in a supersonic expansion, rotational signatures of two cyclic molecules, hydantoin and 2,5-oxazolidinedione, have been unexpectedly observed along with the four most stable conformers of hydantoic acid.Kolesniková, L.; León, I.; Alonso, E. R. et al.: J. Phys. Chem. Lett. 2019, accepted, DOI: 10.1021/acs.jpclett.9b00208.nterestingly, two of them presented folded geometric arrangements that might act as precursors in the cyclization reactions assisted by laser ablation. They could play the role of near-attack conformations (NACs) in the framework of the NAC theory for intramolecular reactions. A detailed analysis of the spectrum further revealed the simultaneous formation of other species in the jet, showing that the laser ablation of solid organic precursors constitutes an alternative tool in the generation of new chemical species.^b It has been recently confirmed using diaminomaleonitrile as a solid precursor. Up to 30 different species (most of them detected in space) have been revealed in the supersonic expansion of our laser ablation chirped pulse Fourier transform microwave LA-CP-FTMW experiment.

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Footnotes:

Kolesniková, L.; León, I.; Alonso, E. R. et al.: J. Phys. Chem. Lett. 2019, accepted, DOI: 10.1021/acs.jpclett.9b00208.I

The formation of so-called complex molecules in the early stages of star formation has implications not only for how we decipher the evolution of planetary systems but also how we understand the evolution of molecules themselves. Interstellar complex molecules, which are simple by terrestrial standards, with only six or more atoms, are key precursors to the rich chemical diversity found in comets and meteorites and on planetary bodies. Isotopologues have proven useful in other areas of chemistry, for instance in pinning down formation mechanisms of molecules in synthetic organic chemistry, but there has been relatively little work done using isotopologues to understand how interstellar molecules form. Isotopologues have been used, however, in constraining the formation of molecules such as methyl cyanide (CH₃CN) and methanol (CH₃OH) in the Orion Kleinmann-Low nebula (Orion KL). Previous low-spatial-resolution studies of methanol in Orion KL have been inconclusive, and thus we have obtained high-resolution imaging data of deuterated methanol (CH₂DOH, CH₃OD) toward Orion KL with the Atacama Large Millimeter/submillimeter Array (ALMA). These data show the distribution of deuterated methanol on spatial scales commensurate with local star formation. Comparing the ratios of CH₂DOH and CH₃OD with ¹³CH₃OH, we aim to assess how methanol chemistry varies across the nebula and determine observationally whether the molecule is formed predominantly on the surfaces of icy dust grains as predicted by laboratory experiments and computational models. These results will be discussed as will the use of isotopologues in the laboratory. Constraining the formation of complex organic molecules in star-forming regions is a first step in understanding how even more complex chemistry-perhaps even prebiotic chemistry-evolved over the history of the universe.

The observation of radioactive isotopes, like ²⁶Al, gives insights in the earlier nucleosynthesis processes of stellar cores. Until now, the characteristic γ-photons released during radioactive decay have been used to record their spatial distribution on a large scale, but this method generally fails to identify individual stellar objects due to the limited detection sensitivity.
An alternative approach is the observation of molecules containing radioactive isotopes, like ²⁶AlF. The stable ²⁷Al-bearing molecule is known to condensate in the outer atmosphere of late-type stars. Radio-telescope facilities, like ALMA, can identify these species via their rotational fingerprint. To enable an unambiguous identification the rotational transition frequencies of ²⁶AlF need to be known with high accuracy.
In this work, the first detection of ²⁶AlF in the merger object CK Vulpeculae is reported. The mass-independent molecular parameterization of AlF using a Dunham approach is shown in detail. Further candidate stellar sources of ²⁶Al will be discussed.

Detection of isomers in the interstellar medium is a valuable tool toward a better understanding of the formation and destruction mechanisms at play, especially because kinetics effects are thought to be as important as thermodynamic ones, if not preponderant. About a third of the interstellar species discovered so far are isomers but little remains known on reactive isomers of relatively large astrophysical species (5 atoms and more), in part due to the difficulty to both produce and detect these species in the laboratory. Ketene is one such species: the molecule is a known interstellar species but none of its isomers has so far been detected by mean of rotational spectroscopy, preventing any interstellar detection so far. We have undertaken an experimental and theoreticcal investigation of the rotational spectrum of the isomers of ketene, and in particular of its two close-shell isomers, hydroxyacetylene (HCCOH) and oxirene (c-C₂H₂O). We will report our results on these compounds and propects of using a recent experimental technique - spectral taxonomy - to investigate isomers of astrophysical interest in the millimeter and submillimeter domains.

Two compounds with a C₂H₄O₂ formula have been detected in the Interstellar Medium (ISM): acetic acid (CH₃CO₂H) and methyl formate (CH₃OC(O)H), the latter being thermodynamically less stable than the former but more abundant. Among the higher homologues with a C₃H₆O₂ formula where a hydrogen atom in C₂H₄O₂ has been replaced by a CH₃ group, two compounds have already been detected: ethyl formate (EtOC(O)H) and methyl acetate (CH₃OC(O)CH₃). The higher thermodynamic stability of another isomer, the propionic acid (EtCO₂H), pushed us to record its rotational spectrum, since this compound has a high probability of being present in the ISM. The methyl top internal rotation should be taken into account, therefore the analysis is performed using RAM36 code.Ilyushin, V.V. et al;J. Mol. Spectrosc. 259, (2010) 26he spectroscopic results and its search in ISM will be presented.
This work was supported by the CNES and the Action sur Projets de l'INSU, PCMI

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Footnotes:

Ilyushin, V.V. et al;J. Mol. Spectrosc. 259, (2010) 26T

The radical, first observed by Herzberg and Ramsay,Herzberg and Ramsay, J. Chem.\ Phys. 20 (1952) 347s dominated by a strong Renner-Teller effectDressler and Ramsay, Phil.\ Trans. R. Soc. A 25 (1959) 553iving rise to two electronic states: a bent X̃ ²B₁ ground state and a quasi-linear à²A₁ excited state. The radical has been the subject of numerous high-resolution investigations and its rotational, vibrational, and electronic transitionsHadj Bachir, Huet, Destombes, and Vervloet, J. Molec.\ Spectrosc. 193 (1999) 326; McKellar, Vervloet, Burkholder, and Howard, ibid. 142 (1990) 319; Morino and Kawaguchi, ibid. 182 (1997) 428; and Martin-Drumel, Pirali, and Vervloet, J. Phys. Chem.\ A 118 (2014) 1331ave been measured. In the most recent investigation, a value of the rotational quantum number N as large as 26 could be reached and the line position analysis revealed that, even in the X̃ ²B₁ ground electronic state, an anomalous centrifugal distortion occurs and originates from the strong coupling between the overall rotation and the bending ν₂ mode, as in the case of the water molecule.Camy-Peyret and Flaud, Molec. Phys. 32 (1976) 523wo theoretical approaches accounting for the Renner-Teller effect are setup to compute the rovibronic energy levels of . The first one is an effective approach in which the large amplitude bending mode and the overall rotation are treated simultaneously.Coudert, Gans, Garcia, and Loison, J. Chem. Phys. 148 (2018) 054302he second one is an exact approach, based on a tridimensional potential energy surface, in which all three vibrational modes are considered in addition to the overall rotation.Coudert, Gans, Holzmeier, Loison, Garcia, Alcaraz, Lopes, and Röder, J. Chem.\ Phys. 149 (2018) 224304n the talk, both approaches will be tested fitting experimental high-resolution data pertaining to the radical. The first approach will be applied to data involving the ground and (010) vibrational states. The second approach should allow us to treat any vibrational states and to adjust the tridimensional potential energy surface of the radical.Jensen, Odaka, Kraemer, Hirano and Bunker, Spectrochim. Acta Part A 58 (2002) 763html:<hr /><h3>Footnotes: Herzberg and Ramsay, J. Chem.\ Phys. 20 (1952) 347i Dressler and Ramsay, Phil.\ Trans. R. Soc. A 25 (1959) 553g Hadj Bachir, Huet, Destombes, and Vervloet, J. Molec.\ Spectrosc. 193 (1999) 326; McKellar, Vervloet, Burkholder, and Howard, ibid. 142 (1990) 319; Morino and Kawaguchi, ibid. 182 (1997) 428; and Martin-Drumel, Pirali, and Vervloet, J. Phys. Chem.\ A 118 (2014) 1331h Camy-Peyret and Flaud, Molec. Phys. 32 (1976) 523T Coudert, Gans, Garcia, and Loison, J. Chem. Phys. 148 (2018) 054302T Coudert, Gans, Holzmeier, Loison, Garcia, Alcaraz, Lopes, and Röder, J. Chem.\ Phys. 149 (2018) 224304I Jensen, Odaka, Kraemer, Hirano and Bunker, Spectrochim. Acta Part A 58 (2002) 763