Surface reactions of radicals play important roles in the formation of complex molecules on interstellar dust grains. Under interstellar conditions, because the coverage of adsorbates on dust is significantly low, surface reactions are often limited by precedent processes, namely, the adsorption and diffusion of reactants. Therefore, to appropriately incorporate dust surface reactions into chemical models, information on the adsorption and diffusion of radicals is crucial. However, it is not easy to follow the behaviour of radicals on surfaces by conventional experimental methods. To monitor radicals on interstellar dust analogues, we have recently succeeded in applying a combination of photostimulated desorption and resonance-enhanced multiphoton ionization methods. In this paper, we briefly review our recent experiments for clarifying radical behaviour on water ice, pure solid CO and diamond-like carbon.

Episodic accretion is an important process in the evolution of young stars and their surroundings. A consequence of an episodic accretion event is a luminosity burst, which heats the protostellar environment and has a long lasting impact on the chemical evolution of the disk and envelope of young stars. We present a new model for the chemistry of episodic accretion based on the 2D radiation thermo-chemical disk code ProDiMo. We discuss the impact of an episodic accretion burst on the chemical evolution of CO and its observables. Furthermore we present a model for the outbursting source V883 Ori where we fitted available observational data to get an accurate physical structure that allows for a detailed study of the chemistry.

Recent observations revealed that there is a difference in the spatial distribution of both nitrogen and oxygen bearing species towards massive star forming regions. These differences can be explained under different temperature regimes in hot cores. In this study, we attempt to model the chemistry of few nitrogen species; namely, vinyl cyanide (CH2CHCN), ethyl cyanide (CH3CH2CN), and formamide (NH2CHO), using gas-grain chemical models. A special attention is given to the role and efficiency of surface chemistry as it is suggested to play one of the main key roles in manufacturing these species.

Thermal desorption experiments of Formamide (NH2CHO) and methylamine (CH3NH2) were performed in LERMA-Cergy laboratory to determine the values of the desorption energies of formamide and methylamine from analogues of interstellar dust grain surfaces, and to understand their interaction with water ice. We found that more than 95 % of solid NH2CHO diffuses through the np-ASW ice surface towards the graphitic substrate, and is released into the gas phase with a desorption energy distribution Edes = (7460 – 9380) K, measured with the best-fit pre-exponential factor A=1018 s-1. Whereas, the desorption energy distribution of methylamine from the np-ASW ice surface (Edes =3850-8420 K) is measured with the best-fit pre-exponential factor A=1012s-1. A fraction of solid methylamine, of about 0.15 monolayer diffuses through the water ice surface towards the HOPG substrate, and desorbs later, with higher binding energies (5050-8420 K), which exceed that of the crystalline water ice (Edes =4930 K), calculated with the same pre-exponential factor A=1012 s-1.

The search for complex organic molecules in the interstellar medium (ISM) has revealed species of ever greater complexity. This search relies on the progress made in the laboratory to characterize their rotational spectra. Our understanding of the processes that lead to molecular complexity in the ISM builds on numerical simulations that use chemical networks fed by laboratory and theoretical studies. The advent of ALMA and NOEMA has opened a new door to explore molecular complexity in the ISM. Their high angular resolution reduces the spectral confusion of star-forming cores and their increased sensitivity allows the detection of low-abundance molecules that could not be probed before. The complexity of the recently-detected molecules manifests itself not only in terms of number of atoms but also in their molecular structure. We discuss these developments and report on ReMoCA, a new spectral line survey performed with ALMA toward the high-mass star-forming region Sgr B2(N).

Experimental evidence for the formation of hydrogenated fullerene molecules is presented. Films of C60 were grown on a highly oriented pyrolytic graphite (substrate) and exposed to a beam of deuterium atoms. Thermal desorption combined with mass spectrometry was used to determine the deuterated fullerene products formed, revealing a maximum degree of deuteration corresponding to C60D36. Release of D2 from the deuterated C60 film occurs at a much higher temperature than for D-saturated graphite.

VLT instruments and ALMA with their high spatial resolution have revolutionized in the past five years our view and understanding of how disks turn into planetary systems. This talk will briefly outline our current understanding of the physical processes occurring and chemical composition evolving as these disks turn into debris disks and eventually planetary systems like our own solar system. I will especially focus on the synergy between disk structure/evolution modeling and astrochemical laboratory/theoretical work to highlight the most recent advances, and open questions such as (1) how much of the chemical composition in disks is inherited from molecular clouds, (2) the relevance of snowlines for planet formation, and (3) what is the origin of the gas in debris disks and what can we learn from it. For each of the three, I will outline briefly how the combination of theory/lab astrochemistry, astrophysical models and observations are required to advance our understanding.

Polycyclic Aromatic Hydrocarbon (PAHs) molecules are attracting much attention in the astrophysical and astrochemical communities because of their ubiquitous presence in space due to their ability to survive in the harsh environmental conditions of the interstellar medium (ISM). The objective of this work is to provide gas phase, high-resolution spectroscopic data on the electronic and vibronic transitions of PAHs and their nitrogenated derivatives measured in astrophysically relevant conditions.

The Belgian Repository of fundamental Atomic data and Stellar Spectra (BRASS) aims to provide one of the largest systematic and homogeneous quality assessment to date of literature atomic data required for stellar spectroscopy. By comparing state-of-the-art synthetic spectrum calculations with extremely high-quality observed benchmark spectra, we have critically evaluated fundamental atomic data, such as line wavelengths and oscillator strengths, for thousands of astrophysically-relevant transitions found in the literature and across several major atomic data repositories. These proceedings provide a short overview of the BRASS project to date, highlighting our recent efforts to investigate and quality-assess the atomic literature data pertaining to over a thousand atomic transitions present in FGK-type stellar spectra. BRASS provides all quality assessed data, theoretical spectra, and observed spectra in a new interactive database under development at brass.sdf.org.

Ubiquitous strong mid-infrared emission bands are observed towards many objects and are attributed to interstellar Polycyclic Aromatic Hydrocarbons (PAHs). PAHs are ionized, or even dissociate, when exposed to strong interstellar radiation fields. By means of ion trap mass spectrometry, light-induced dissociation patterns of PAH cations are measured and the mid-infrared spectroscopic signatures of the parent ion and its dissociation products are characterized. These results are then combined with density functional theory (DFT) calculations to obtain insight into the dissociation characteristics of interstellar PAHs at a molecular level.

The surfaces of interstellar and circumstellar dust grains are the sites of molecule formation, most of which, except H2, stick and form ice mantles. The study of ice evolution thus seems directly relevant for understanding our own origins, although the relation between interstellar and solar system ices remains a key question. The comparison of interstellar and solar system ices relies evidently on an accurate understanding of the composition and processes in both environments. With the accurate in situ measurements available for the comet 67P/Churyumov-Gerasimenko with the Rosetta mission, improving our understanding of interstellar ices is the more important. Here, I will address three specific questions. First, while laboratory experiments have made much progress in understanding complex organic molecule (COM) formation in the ices, the question remains, how does COM formation depend on environment and time? Second, what is the carrier of sulfur in the ices? And third, can ice absorption bands trace the processing history of the ices? Laboratory experiments, ranging from infrared spectroscopy to identify interstellar ice species, to surface experiments to determine reaction parameters in ice formation scenarios, to heating and irradiation experiments to simulate space environments, are essential to address these questions and analyze the flood of new observational data that will become available with new facilities in the next 2-10 years.

Effective Landé g-factors (geff) are fundamental quantities in order to derive stellar magnetic field intensities. The determination of geff involves both total angular momenta and Landé g-factors of the transition levels. Theoretical g-factors are generally adopted, and the corresponding geff, often quite different from the one obtained in laboratory, affects the accuracy on magnetic field strength measurements. In this work we discuss a method to experimentally determine geff for highly ionised species, based on high resolution spectropolarimetry applied to Electron Cyclotron Resonance laboratory plasmas.

Two laboratory emission spectrometers have been designed and described previously. Here, we present a follow-up study with special focus on absolute intensity calibration of the new SURFER-spectrometer (SUbmillimeter Receiver For Emission spectroscopy of Rotational transitions), operational between 300 and 400 GHz and coincident with ALMA (Atacama Large Millimeter/submillimeter Array) Band 7.

Furthermore, we present a feasibility study to extend the detection frequencies up to 2 THz. First results have been obtained using the SOFIA (Stratospheric Observatory for IR Astronomy) upGREAT laboratory setup which is located at the University of Cologne. Pure rotational spectra of the complex molecule vinyl cyanide have been obtained and are used to give an estimate on the sensitivity to record ro-vibrational transitions of molecules with astrophysical importance at 2 THz.

Syntheses of carbon dust analogues are key experiments in laboratory astrophysics, as an approach to study some chemical and topological features of interplanetary and interstellar carbon dust. We report a comparative experimental study for carbon dust analogues obtained in (1) an atmospheric pressure dielectric barrier discharge (DBD), fed with helium – saturated hydrocarbons gas mixtures, (2) a low pressure radio frequency (RF) discharge and (3) a pulsed laser deposition (PLD) experiment with a Nd:YAG laser and a graphite target. The aliphatic –C–H stretching band, known as the 3.4 micron feature, as well as the CH2/CH3 ratio, the H/C ratio value and the physical appearance at microscopic scale, show a variability that is influenced by the synthesis method and the experimental parameters of each specific technique.

Interstellar carbon has been detected in both gas-phase molecules and solid particles. The goal of this study is to identify the link between these two phases of cosmic carbon. Here we report preliminary results on the low temperature formation of carbonaceous dust grains from gas-phase aromatic hydrocarbon precursors. This is done using the supersonic expansion of an argon jet seeded with aromatic molecules and exposed to an electrical discharge. We report experimental evidence of efficient carbon dust condensation from aromatic molecules including benzene and naphthalene. The molecular content of the solid grains is probed with laser desorption mass spectrometry. The mass spectra reveal a rich molecular composition including fragments of the parent molecule but also growth into larger molecular species.

Recent experimental and theoretical works concerning gas-phase radical-neutral reactions involving Complex Organic Molecules are reviewed in the context of cold interstellar objects with a special emphasis on the OH + CH3OH reaction and its potential impact on the formation of CH3O.

Polycyclic aromatic hydrocarbons (PAH) and their derivatives, including protonated and cationic species, are suspected to be carriers of the unidentified infrared (UIR) emission bands observed from the galactic and extragalactic sources. We investigated the infrared (IR) spectra of protonated nonplanar PAHs: corannulene (C20H10) and sumanene (C21H12), that are regarded as a fragments of a fullerene,C60. The protonated corannulene H+ C20H10 and sumanene H+ C21H12 were produced in seperate experiments by bombarding a mixture of corannulene/sumanene and para-hydrogen (p-H2) with electrons during deposition at 3.2 K. During maintenance of the electron-bombarded matrix in darkness the intensities of IR lines of protonated corannulene decreased because of neutralization by electrons that were slowly released from the trapped sites whereas the hydrogenated species were produced. The observed lines were classified into several groups according to their responses to darkness and secondary irradiation at 365 nm/385 nm LEDs. Spectral assignments were derived based on a comparison of the observed spectra with those predicted with the B3PW91/6-311+ +G(2d,2p) method. The observed IR spectrum of hub-H+ C20H10, the most stable protonated isomer, resembles several bands of the Class-A UIR bands.

Chemistry in the interstellar medium is generally out-of-equilibrium and as such is kinetically controlled by a set of time-dependent equations, both for gas-phase chemistry and solid-state chemistry. The competition between the different possible reactions will determine toward which complex molecules the chemical network is driven to. The formation of complex molecules on the surface of the grains or in the ice mantle covering them is set by the diffusion-reaction equation, which is depending on temperature dependent reaction rate constants and diffusion coefficients. This paper shows how these two parameters can be experimentally determined by laboratory experiments. It also shows how the ice mantle reorganization plays an important role in the trapping and reactivity, which leads to the formation of complex organic molecules.

We describe recent simulations of interstellar and laboratory ices using the 3-D, off-lattice microscopic Monte Carlo kinetics model MIMICK. The simulations indicate that interstellar ices are capable of achieving porous structures, dependent on physical conditions. In some cases, such structures may be filled as they are formed, by mobile/volatile species such as H2 that become trapped in those structures. Simulations of laboratory water-ice deposition using MIMICK suggest that an additional non-thermal diffusion mechanism is required to reproduce the high degree of porosity achieved for experimental ices at temperatures less than ~80 K. This mechanism is related to the deposition process itself. Simulations of temperature-programmed desorption of mixed molecular ices are ongoing. The interstellar models have also recently been developed to incorporate a full gas-phase chemistry, coupled with the grain-surface chemistry.

The Titan Haze Simulation (THS) experiment is a unique experimental platform that allows to simulate Titan’s complex atmospheric chemistry at low Titan-like temperature by generating a plasma discharge in the stream of a plasma jet expansion. Both gas and solid phase products are generated and can be analyzed using different in-situ and ex-situ diagnostics. Here, we present an overall description of the work accomplished with the THS in the last 10 years, our current research efforts, and the important implications for the analysis of Cassini’s returned data and preparation for future Titan missions.