Themed collection Astrochemistry at high resolution

Martin McCoustra, Chair of the Scientific Organising Committee, introduces the Faraday Discussion volume on Astrochemistry at high resolution.

We investigate possible chemical conditions on a canonical Hycean world, focusing on the present and primordial molecular composition of the atmosphere, and the inventory of bioessential elements for the origin and sustenance of life in the ocean.

The Mid-InfraRed Instrument/Medium-Resolution Spectrometer (MIRI/MRS) on board the James Webb Space Telescope reveals the rich and diverse chemistry in the planet forming regions around Sun-like and low-mass stars.

This paper presents a brief history of astrochemistry, summarises recent research presented at this Faraday Discussion and offers some thoughts on the future development of the subject.

We present an astrochemical modeling study with the aim of comparing shock chemistry traced by HNCO and SiO in two distinctively different environments: the AGN dominated region in the CND of NGC 1068 and the starburst-dominated region in the CMZ of NGC 253.

We use Bayesian inference together with the MOPED compression algorithm to help determine which species should be prioritised for future detections in order to better constrain the values of binding energies in the ISM.

Direct frequency comb spectroscopy of HCN is performed using a high resolution, cross-dispersed spectrometer. Short-wave and mid-wave infrared instrumentation for precision molecular spectroscopy to test line lists is discussed.

This Spiers Memorial Lecture introduces the Faraday Discussion on ‘Astrochemistry at high resolution’, focusing on the special case of interstellar complex organic molecules (iCOMs).

Early results from JWST-MIRI programs on low- and high-mass protostars and disks show significant diversity in their mid-infrared spectra, most notably for CO₂, H₂O and C₂H₂. Benzene is detected in disks around very low mass stars.

Low temperature kinetics, crossed beam experiments, calculations of the underlying potential energy surface and of the product branching fractions for the N(²D) + benzene reaction are reported. The results have been used in a photochemical model of Titan.

The first AGB chemical kinetics model that includes porosity, dust–gas chemistry and companion UV photons, allows us to unravel the interplay of the complexities and identify suites of molecules to determine the presence of a companion star.

The first rovibrational (IR) and rotational (mm-wave) spectra are measured for c-C₃H₂D⁺, a potential detection target in interstellar space.

The reaction of NH₂ and CH₃CHO becomes fast at low temperatures, and may be a potential source of CH₃CO radicals in the interstellar medium.

Silicates are the main constituent of interstellar dust. Direct observations of nanometre-sized silicate grains would provide a smoking gun for the occurrence of grain condensation in the diffuse interstellar medium.

We analyse deuterated water (HDO) and sulfur dioxide (SO₂) at high-angular resolution in the binary system SVS13-A. We propose that molecular emission is produced by an accretion shock at the interface between the accretion streamer and the disk.

Resonant excitation of CO and water-containing ices with a free-electron laser leads to CO photodesorption.

Fragmentation pathways of benzonitrile and pyridine are elucidated using cryogenic infrared ion spectroscopy, quantum-chemical calculations and molecular dynamics simulations.

Our systematic computational study suggests that the nature of the binding site or the reaction site has a significant effect on the computed binding energies or reaction barriers.

Continuous-wave-cavity ring-down spectroscopy (CRDS) coupled with a pulsed uniform supersonic flow (Laval flow) are used to measure the reaction kinetics of the reaction of CN (v = 1) with 1,3- and 1,2-butadiene isomers at low temperature.

Flash vacuum pyrolysis or DC discharge are exploited for the production of unstable/reactive species. A strategy relying on the interplay of experiment and theory is presented, which ultimately leads to line catalogs for astronomical searches.

Cometary ice analogs: amorphous H₂O ice can trap other molecules up to ∼30% by number, which are outgassed during ice crystallization (130 K to 150 K). Beyond 160 K, crystalline ice sublimes with only a minor fraction (<1%) of other molecules with it.

Destruction of large, interstellar organic molecules with high proton affinities is amplified due to proton transfer from NH₄⁺. Chemical kinetic models indicate a strong destructive effect on NH₂-bearing species, including methylamine and glycine.

The UV photodesorption of neutrals from ices comprising HCOOH and HCOOCH₃ is studied. Photodesorption yields are provided from a variety of different desorbing species, highlighting the preponderant role played by photodissociation of the organics.

Laboratory rotational spectra of norbornadiene and its cyano derivatives were recorded using chirped-pulse millimetre-wave spectroscopy. These molecules were then searched for in the starless core TMC-1 using the QUIJOTE line survey.

The so-called molecular ring has been mostly absent from astrochemical observations despite containing the bulk of the Milky Way’s molecular matter. A pilot survey of 11 molecular-ring giant molecular clouds with ALMA reveals new chemical stockrooms.

The radiative cooling rate of cationic 1-cyanonaphthalene is determined from storage ring experiments and shown to be consistent with recurrent fluorescence. The rapid cooling helps explain the abundance of the neutral molecule in molecular clouds.

Calculated infrared absorption intensities of PAHs that underlie the interpretation of infrared emission from the ISM are validated with experiments. An adjusted emission model implies that typical PAH sizes are smaller than previously estimated.