Dutch Astrochemistry Network

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Publication: Netherlands Organisation for Scientific Research (NWO) NWO Domain Science

E: astrochemistry@nwo.nl W: www.nwo.nl/astrochemistry

April 2018

Dutch Astrochemistry Network – II

Netherlands Organisation for Scientific Research Colophon

Text: Dutch Astrochemistry Community

Coordination and editing: Sebastiaan de Vet

Design: Christy Renard (Communications)

Printed by: Ipskamp printing

On the cover: Detail of the Galactic Plane visible from the southern hemisphere imaged during the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL). The APEX data, at a wavelength of 0.87 millimetres, shows up in red and the background blue image was imaged at shorter infrared wavelengths by the NASA Spitzer Space Telescope as part of the GLIMPSE survey. The fainter extended red structures come from complementary observations made by ESA’s Planck satellite. Credits: ESO/APEX/ATLASGAL consortium/NASA/ GLIMPSE consortium/ESA/Planck Dutch Astrochemistry Network – II

The Hague, April 2018 Netherlands Organisation for Scientific Research 2

Figure 1 Illustration of the lifecycle of molecules in the interstellar medium. Chemical processes take place at every stage in this process – from the birth of molecules in circumstellar shells, their passing through the physical gauntlet of the interstellar medium ultimately fuelling star and planet formation – and this controls the organic inventory of planetary systems. Preface

In 2010, the Netherlands Organisation for Scientific Research (NWO) funded the Dutch Astrochemistry Network as a coherent and integrated research program in the physics and chemistry of molecules in space involving all the major players in this field in the Netherlands. DAN-II is a continuation of this highly successful program. Dutch researchers are very active in astronomical observations and astrophysical modelling of the molecular Universe, in laboratory studies on the spectroscopic properties and excitation rates of astronomically relevant species, and in characterizing the surfaces of materials of astronomical relevance and the reactions thereon using experimental and quantum-chemical tools.

3 Astrochemistry

The origin and evolution of the molecular universe starts with the injection of material – much of it in molecular form – by stars in the later stages of their life. Subsequently, this material is processed in the interstellar medium by the prevalent ultraviolet radiation fields, energetic particles, and strong shocks. During their sojourn in the interstellar medium of galaxies, simple molecules and atoms combine to form larger species, they condense into ices where further chemical processing occurs in a bottom-up process. At the same time, complex molecules formed in stellar ejecta are broken down to smaller species by strong UV fields in a top-down fashion. Eventually, these simple and complex molecules can end up in the comets, asteroids, and planets of young protoplanetary disks. This ‘chemical dance’ of the elements leads to a rich and varied chemical inventory in the interstellar medium of galaxies. A major goal of 4 astrochemistry is to understand this chemical diversity under the extreme conditions of space.

Over the last 10 years, the reigning paradigm – life on Earth is unique – has shifted towards the opinion that life could be a common characteristic of the Universe. We have discovered that there are billions and billions of planets in our own Milky Way alone. Furthermore, it has been found that life started really very quickly on the early Earth and that life in the form of extremophiles can bloom under very adverse conditions on Earth. As a result, the key question has shifted from ‘Are we alone?’ to ‘How can we best search for the biomarkers of life on other planets in our Solar system and beyond?’. Life as we know it is largely chemical in nature. Therefore, studies on the origin of life start with astrochemistry and the quest to understand the raw materials of life produced by chemical evolution in space and how these are delivered to new planetary systems.

During their evolution in space, molecules exert a direct influence on their environment. Molecules dominate the cooling of gas inside dense molecular clouds. Molecules also control the ionization balance in such environments and thereby the coupling of magnetic fields to the gas. Through this influence on the forces supporting clouds against gravity, molecules will affect the process of star formation. Large molecules are also thought to be a major contributor to the heating of diffuse atomic gas in the interstellar medium. Thereby they affect the physical conditions in such environments and the phase structure of the interstellar medium, which sets the stage for the star formation process.

Molecules provide also key probes of the Universe. Molecules possess a myriad of electronic, vibrational, and rotational levels whose excitation is sensitive to the local physical conditions over a wide range of astrophysically relevant densities and temperatures. Molecular abundances are also sensitive to the local physical conditions. Hence, molecules provide a sensitive tool to study the dynamics and the physical and chemical conditions in a wide range of objects at scales ranging from protoplanetary systems to galactic 5 and extragalactic scale-sizes.

Molecules are directly interwoven into the fabric of the universe. They are an important component of the Universe and play a central role in many key processes that dominate the structure and evolution of galaxies. Understanding the origin and evolution of interstellar and circumstellar molecules is therefore a fundamental goal of modern astrophysics. Likewise, developing molecules as an astronomical tool to study the physical conditions and dynamics of a wide variety of objects in the Universe will be of key importance for astronomy in the coming decade. Furthermore, understanding the organic inventory of newly forming planetary systems, in particular in the habitable zone, may provide deep insight in the starting point of life in the Universe. National and international context Progress in astrochemistry is very much driven by new astronomy missions and the new views of the Universe that they open up. The Atacama Large Millimeter/submillimeter Array (ALMA) has become operational in 2013, allowing astronomers and astrochemists to study molecules in space in the sub- millimetre wavelength range. ALMA combines high sensitivity and high angular resolution, allowing revolutionary images of molecules in different environments to be made and resolving chemically different zones down to scales of a few astronomical units. The project benefits from a strong Dutch involvement. The Band 9 (602-720 GHz) receivers were built by the Netherlands Research School for Astronomy (NOVA). The Band 5 (162-211 GHz) receivers are currently also being produced by NOVA and will become operational during the DAN-II period. Over the last decade, the Spitzer Space Telescope and the Herschel Space Observatory, launched by the National Aeronautics and Space Agency (NASA) in 2003 and the European Space Agency (ESA) in 2009, respectively, have opened up the mid- and far-infrared sky for detailed spectroscopic studies of molecules. In 2020, NASA foresees the launch of the James Webb Space Telescope (JWST), a 6.5 meter telescope which promises even higher spectral & spatial resolution and sensitivity at mid-IR wavelengths. Indeed, the Mid InfraRed Instrument (MIRI) and the Near-InfraRed Spectrograph (NIRSPEC) will allow, for the first time, mid-infrared spectral 7 images to be made at sub-arcsecond resolution. This wavelength range is spectroscopically very rich and contains unique astrochemically relevant probes, including H2 and HD pure rotational lines, molecular rotation-vibration and pure rotation lines from small molecules (e.g., C2H2, CO2, HCN, NH3, SO2, H2O and OH), vibrational bands of PAHs and fullerenes, and vibrational bands of many ice components. NOVA is responsible for the design and building of the Spectrometer Main Optics Module (SMO) of MIRI. With these observatories, astrochemistry is poised to tackle key questions in astronomy; in particular, the distribution of organic material in the habitable zone of planet-forming disks around young stars and the processes that play a role in their origin and evolution. In the more distant future, these results feed into preparation for science with the METIS instrument for the Extremely Large Telescope (ELT), in which NOVA has the PI role.

Over the last few years, new methods in physical chemistry have been developed that carry the promise of opening up new avenues of research in astrochemistry. Various chemistry and molecular physics groups in the Netherlands are very active in this arena. These new physical chemistry methods include, in particular, the development of new numerical methods and software for fast calculation of inelastic collisional cross sections, including systems with a deep potential well. In addition, (cooled) ion traps allow, for the first time, the study of the photophysics and characteristics of large molecules and their fragmentation products. Such studies also benefit from newly developed sensitive state-selective detection techniques including IR-UV ion-dip schemes coupled with molecular beam and resonance- enhanced multiphoton ionization techniques combined with cavity-ringdown spectroscopy and velocity map imaging. The development of unique capabilities in performing collision experiments using molecular state cooling and manipulation techniques such as Stark decelerated molecular beams in combination with velocity mapped ion imaging will allow measurement of differential excitation cross sections. Ice chemistry studies will profit from low temperature surface chemistry techniques combining in-situ reflection absorption techniques with laser desorption and time of flight mass spectrometry detection. In addition, velocity map imaging (VMI) techniques have been extended to allow the study of molecular dynamics of photo-induced processes taking place at icy surfaces. On the quantum chemistry side, ab-initio and Density Functional Theory (DFT) techniques have steadily improved and allow for accurate calculations even on large species. Finally, new self-consistent 2D chemo-physical models of protoplanetary disks allow for detailed studies of gas phase and ice chemistry under a wider range of 8 astrophysical conditions. These developments now enable us to address questions and systems that could only be dreamt of 10 years ago.

The developing international perspective

Over the years, Dutch astrochemistry has benefitted from international networks. Specifically, the first Dutch Astrochemistry Network built upon the Marie Curie Initial Training Network ‘The Molecular Universe’ (2004-2008, coordinator: Xander Tielens) funded by the EU under FP6. This network was set up to support the analysis and interpretation of the HIFI instrument build by a large international consortium under the guidance of the SRON Netherlands Institute for Space Research. The HIFI instrument flew on the Herschel Space Observatory, launched by ESA in 2009. One of the key objectives of DAN was to study the organic inventory of regions of star and planet formation with HIFI. DAN also worked closely with the successor of ‘The Molecular Universe’, the LASSIE Network (2010-2014; research coordinator: Harold Linnartz), which focused on solid state astrochemistry issues that are of relevance for the chemical evolution of the Universe. This was also one of the themes of DAN and this has led to much synergy. On the educational side, joint summer schools were organized that were attended by students from both networks. In a similar way, DAN-II will coordinate its research in the Aromatic Universe theme with the Marie Curie Innovative Training Network, EUROPAH (2017-2021; research coordinator: Xander Tielens) funded under Horizon2020. EUROPAH investigates the extensive and ubiquitous role of PAHs in space a topic much aligned with the Aromatic Universe theme of DAN-II. As one immediate result, the DAN-II funding has been leveraged through joint research projects to further appointments. A first DAN-II summer school in collaboration with the EUROPAH network was organized in April 2018.

In the framework of DAN (the precursor of DAN-II) NWO and NASA have launched a collaborative venture, when the two parties signed a Memorandum for the Record in 2010. This Memorandum paved the way for exchange and cooperation with the NASA Ames Research Center’s network Carbon in the Galaxy. It has been instrumental in facilitating close collaboration, and has resulted in multiple exchanges and increased joint scientific output. NWO’s commitment to cooperation was a significant factor in helping NASA Ames Research Center to acquire funding for the NASA Astrobiology Institute (NAI) node. The 2016 Space Act between NASA and NWO has taken this collaboration to the next level 9 and forms a basis for cooperation for the coming years. With this agreement in place, joint research projects and new research initiatives can be implemented, while the parties involved can push ahead with joint workshops and researcher exchanges. Moreover, the collaborative framework will provide access to key facilities and will support joint participation in international experiments. A joint network meeting was organized at the 245th meeting of the American Chemical Society in Washington DC during August 2017 to explore future cooperative projects. The Goddard Center for Astrobiology (GCA) at the NASA Goddard Space Flight Center also joined in to explore complementary projects. Network goals and objectives The Dutch Astrochemistry Network is a highly interdisciplinary network combining the astronomical and chemical expertise in the Netherlands with the goal of understanding the origin and evolution of molecules in space and their role in the Universe.

The field of molecular astrophysics is a highly interdisciplinary field where molecular physics, laboratory spectroscopy, surface science, theoretical chemistry, astrochemistry, astronomical observations, and astronomical modelling intersect. The Dutch Astrochemistry Network has been specifically designed to bridge these disciplines with a coherent approach to astrochemistry leveraging the physical chemistry

Figure 2 The Atacama Large Millimeter/submillimeter Array (ALMA), on the Chajnantor Plateau in the Chilean Andes. The Large and Small Magellanic Clouds, two companion galaxies to our own Milky Way galaxy, can be seen as bright smudges in the night sky, in the centre of the photograph. Credit: ESO/C. Malin expertise and facilities in the Netherlands to address key astronomical questions. Building upon the results from DAN-I, three major astrochemical themes have been identified for DAN-II where Dutch astronomy and chemistry have particular strong expertise and experience as well as access to unique observational or experimental facilities. The three selected themes are:

1. The gaseous molecular Universe where formation and destruction as well as the excitation of simple molecules are studied; 2. The icy Universe where the role of ices is studied in the origin of molecular complexity in the Universe; 3. The aromatic Universe, which studies the contribution of aromatic species to the molecular inventory and their evolution in space.

Within each theme a number of specific and highly interwoven science projects have been defined that together address the joint astrochemical objectives of that particular theme. For each theme, these 12 projects comprise laboratory studies and/or quantum chemical studies that are then combined with astronomical modelling studies and supplemented by observations of molecules in space. The themes are very complementary with projects addressing common science questions from different perspectives. A key goal of each theme is also to assess the implications for the organic inventory and physical characteristics of planet forming disks. In this way, the network proposes a coherent and integrated end-to-end scientific program that transcends in many ways the goals and objectives of the individual research projects. Further cross-fertilization will occur through the use of complementary experimental, theoretical, and observational techniques. Finally, the network will provide a unique learning experience for the students working on the projects. They will be provided with a well-rounded education where they will experience at first hand the multi-disciplinary approach associated with joint research objectives, as well as the educational efforts provided at the network level such as summer schools in the field of astrochemistry. In this way, the Dutch Astrochemistry Network will create the putative future scientific leaders of this field. 13

Figure 3 An artist impression of the James Webb Space Telescope. Credit: ESA (C. Carreau). NationalTheme 1: and internationalThe gaseous contextUniverse Of the nearly 200 different molecules that have been detected in interstellar space, the vast majority has been observed in the gas phase in interstellar clouds. The James Webb Space Telescope (JWST), in concert with the Atacama Large Millimeter/submillimeter Array (ALMA), will provide the next main push for gas-phase studies. Together, the infrared and millimetre lines allow a number of key questions to be addressed, especially on high temperature (200-1000 K) gas-phase chemistry such as found in the planet- forming zones of disks around young stars. For example, what is their chemical inventory, including the overall C/O and C/N ratios of the gas that may end up in the atmospheres of giant planets? Can we see chemical signatures of the accretion shock as matter enters the forming disk? What is the origin of chemical complexity: gas or ice? Also, what does the molecular excitation tell us about the physical structure and impinging radiation field of the emitting gas?

The gas-phase theme focuses on two types of processes that are essential for addressing these questions and in which the Netherlands is particularly strong.

Specifically, it includes a theoretical study (Nijmegen) on state-to-state inelastic collision rate coefficients 15 for rotational-vibrational transitions of molecules that will be prime targets for JWST (i.e. C2H2, CO2, and CH4). This is supported by experimental studies (Nijmegen) on rotational energy transfer of NH3 and H2CO in collisions with H2 using state-of-the-art velocity map imaging that will test these potential energy surfaces and molecular scattering processes to the limit. In addition, the VUV photoabsorption and photodissociation spectrum of CH and more complex, carbon-based radicals will be measured (Amsterdam) using advanced expertise on lasers and detection techniques. These spectra may also provide insight into possible carriers of the Diffuse Interstellar Bands, a century-old mystery in interstellar spectroscopy. These projects will provide key input to state-of-the-art models (Leiden) of the excitation and chemistry of simple molecules in protoplanetary disks and shocks for comparison with guaranteed time observations of JWST. Conversely, sensitivity analyses of the model results will guide the calculations and experiments of the experimental and quantum chemical studies.

The astrochemical models developed for the gas-phase theme link in a very natural way with the other two themes. In particular, PAH’s are part of the chemical networks and their influence on the model results will be studied as well, especially since JWST will automatically cover the PAH bands for the same sources as the gas-phase lines. Similarly, ice absorption bands will be observed with the JWST together with the gas-phase lines toward protostars and will be part of the model analysis of gas/solid ratios. Finally, the photodissociation studies provide key parameters for both gas and in ice mantle chemistry.

Projects in this theme

−− Photo-absorption and dissociation of CH and carbon-based radicals — Prof. Wim Ubachs (VU) −− Protostellar and protoplanetary disk chemistry: from basic data to astrochemical models — Prof. Ewine van Dishoeck (UL) −− Rotation-vibration inelastic collision rates of polyatomic molecules — Prof. Gerrit Groenenboom (RU), Prof. Ad van der Avoird (RU) −− It takes two to tango: bi-molecular (half) collisions of astrochemical relevance — Prof. David Parker (RU), Prof. Bas van de Meerakker (RU)

Figure 4 Simulated JWST-MIRI spectrum of the molecular emission from the inner regions of a protoplanetary disk around a solar-mass star. Note the wealth of ro-vibrational bands of simple molecules. Credit: F. Lahuis. 17

Figure 5 Overview of the gas-phase theme projects and their relations. The JWST-MIRI will provide unique data to the Dutch community (upper left), especially on the planet-forming zones of disks (centre). The analysis of the observations will make use of molecular data obtained from quantum theoretical calculations (lower right). The theory will be tested against laboratory collision experiments making use of Stark decelerator controlled molecular beams and advanced molecular imaging techniques (lower left). The star emits copious UV photons resulting in photodissociation of molecules, whose rates and product branching ratios will be measured and put into models. Credit: NASA/ESA/ESO/Vogels et al., 2015. NationalTheme 2: and Theinternational icy contextUniverse Interstellar ices are composed of mixtures and layers of water, CO2, CO, NH3 and other molecules frozen or formed on cold dust grains. They are the main reservoir of heavy elements in the large clouds in space from which stars and planets form. Ultimately, these ices end up in comets in planetary systems, where they can enrich young planets with the volatiles needed to form oceans and atmospheres, and to construct he building blocks of life. During this voyage, chemical modification by thermal, energetic (ultraviolet photons, cosmic rays, electrons) and non-energetic (atom-addition) processes takes place. As a result rather simple and also complex organic molecules are formed. The primary goal of the four research projects within the icy Universe theme is a quantitative astronomical and chemical characterization of these processes, studied with telescopes, laboratory experiments and astrochemical models.

Figure 6 SURFRESIDE2, a laboratory setup fully optimized to study the formation of molecules on icy grains under dense cloud conditions. Credit: H. Linnartz / Leiden Observatory. The initial ice structure and composition as well as the nature and extent of the modification processes are still surrounded by many questions. This is largely due to the lack of information, both from astronomical observations and ice simulations in laboratories as well as astrochemical models and theoretical calculations. In recent years in situ laboratory experiments have shown that the level of molecular complexity that can be reached in the solid state is high. It comprises small sugars, fats and it is only a matter of time before the first amino acids will be formed under fully controlled conditions. Other laboratory data show how ices evaporate thermally and upon vacuum UV irradiation or undergo structural changes, linking these molecular processes to the position of snowlines in protoplanetary disks. The resulting parameters, reaction networks and rates, are needed as input for astrochemical

Figure 7 ALMA images of molecules in the UV irradiated outer disk zones. Compilation from: Oberg et al.,2015; Loomis et al., 2015 and Guzman et al., 2015. models that bridge typical timescales in a laboratory to those needed to interpret the observational snapshots of interstellar environments, covering millions of years. This is particularly true for the planet formation stage in which ices play a key role and models are needed to visualize how ices behave with time. For example, it is still an open question whether the ices formed in the molecular clouds get incorporated into disks and/or whether the ices form from scratch in the disks again. Within this context, the presence or absence of snowlines determines the efficiency with which planets can form and likely also determines the chemical composition of planets and their moons. Theoretical calculations, finally, focus on the solid state molecular processes, putting a chemical base under the processes at play, such as low temperature surface diffusion and solid state segregation.

With the forseen launch of the JWST in 2020 it is likely that soon new ice molecules will be discovered soon. It is also expected that new data will become available that show how ice in space links to gas phase abundances, molecular complexity and planet formation. The overall goals of the ice theme only can be realized by combining the Dutch expertise in surface and solid state laboratory astrophysics, astronomical observations, astrochemical modelling, and theoretical chemistry. The four projects are 21 highly complementary. The role of ices in protoplanetary disks is studied using ALMA observations and laboratory experiments, both in Leiden and Nijmegen. Theoretical models (Nijmegen) are used to simulate surface events on interstellar ices and astrochemical networks that lead to molecular complexity in space. The latter follows the outcome of experimental studies in the Sackler Laboratory at the Leiden Observatory.

Projects in this theme

−− Circumstellar ice and snow lines - Photochemistry at the edge — Prof. Michiel Hogerheijde (UL), Prof. Harold Linnartz (UL) −− Molecular complexity in interstellar ices – a combined experimental / theoretical study — Prof. Harold Linnartz (UL), Prof. Herma Cuppen (RU) −− Mobility and restructuring in interstellar ices — Prof. Herma Cuppen (RU), Dr Britta Redlich (RU) −− Velocity Map Imaging at Icy Surfaces — Prof. David Parker (RU). 22

Figure 8 Breakdown of gaseous naphthalene leads to the formation of pentalene (2 fused 5-membered rings) as identified by IR action spectroscopy. Facile conversion of 6- to 5-membered ring species supports possible conversion of PAHs to fullerenes. Credit: Bouwman et al., Chem. Commun. 2016, 52, 2636-2638. Theme 3: The aromatic Universe Polycyclic aromatic hydrocarbon (PAH) molecules are now widely accepted to be omnipresent in the interstellar medium (ISM), as evidenced by the observation of a diagnostic set of emission bands in the IR spectra of nearly all inter- and circumstellar objects. The emission is due to radiative cooling of these PAH species taking place after UV excitation. An estimated 10% of all interstellar carbon atoms may be in the form of PAHs, having an average size in the range of 50 to 100 C-atoms. The presence of PAHs not only influences the IR signatures of interstellar objects, but is also hypothesized to have pronounced influence on the chemical evolution of the ISM. For instance, PAHs may affect the charge and heat balance, drive H2 formation, initiate and sustain grain and dust formation, and lead to greater molecular complexity involving perhaps even biogenic molecules.

Both spectroscopy and chemical evolution of PAHs can be studied, by experiment as well as theory, in our laboratories under conditions that – to some extent – resemble those of interstellar environments. Where DAN-I addressed such studies on relatively small, widely available PAH molecules, DAN-II will push these studies forward towards PAHs of larger, astrophysically relevant sizes. Increasing the size of 24 the systems inherently increases complexity. DAN-II will address the challenges related to increasingly complex experiments and computations. How can we maintain good spectral resolution for increasingly complex systems? What are the levels of theory that provide the best compromise between efficiency and accuracy for such large systems? To what extent can we map the dissociation pathways of large PAHs, for which a virtually infinite number of paths seem imaginable? Can we resolve branching ratios between different pathways for such large systems? With larger system sizes comes also the possibility of isomerization between different carbon allotropes, such as fullerenes and diamondoids; here we can truly start to investigate whether there are chemical routes ‘from rings to planes and cages’. And with higher degrees of curvature of the PAH comes higher reactivity. Moreover, π-stacking interactions become substantial for large PAHs and spectroscopic investigations of non-covalently bound PAH clusters are an interesting but uncharted territory.

The research projects within the Aromatic Universe theme of DAN-II combine expertise at Amsterdam, Leiden, Nijmegen and Utrecht. They are highly interwoven as experimentalists will work in close collaboration with theorists within this theme and across the entire Network. Several of the projects involving experimental IR spectroscopy make use of the free electron laser FELIX and various mass spectrometry-based action spectroscopy schemes. Studies involving UV spectroscopy will cross-connect with spectroscopic investigations of smaller species in the Gaseous Universe theme of DAN-II. The Figure 9 : PAH and fullerene cations are isolated in an ion trap and irradiated by UV/VIS laser light at different fluences. After irradiation, the products are analysed with a time-of-flight mass spectrometer. Left: irradiation at 266 nm. Fullerenes evolve by sequential loss of C2 units, shrinking their cages. The presence of magic numbers reflects the stability of the species formed. PAHs are quickly stripped of their H atoms and then evolve also by loss of C2 units. The pattern of magic numbers mimics that of the fullerenes. Right: irradiation at 532 nm. Buckminsterfullerene, C60, does not absorb at 532 nm and does not evolve even at 25 very high laser fluences. For comparison, C70 breaks down to C60 when further evolution is halted. Likewise, starting with the large PAH C66H26 leads to a highly enhanced C60 production, providing evidence that buckminsterfullerene is also formed by laser processing of this species. Credit: J. Zhen. involvement of a surface science group focusing on PAHs on surfaces is novel in DAN-II and allows for interesting comparisons with gaseous species. At the same time it provides a natural connection to the Icy Universe theme of the Network.

Projects in this theme

−− High-resolution vibrational and electronic spectroscopy of the isolated aromatic Universe — Prof. Wybren Jan Buma (UvA), Dr Anouk Rijs (RU) −− Reactions of PAHs: a route to chemically complex molecules? — Prof. Matthias Bickelhaupt (VU), Dr Ingmar Swart (UU) −− Photo-processing, reactivity and spectroscopic characteristics of large PAHs and their derivatives — Prof. Jos Oomens (RU), Prof. Xander Tielens (UL) −− The Reaction Dynamics of Ionic and Neutral PAHs — Dr Annemieke Petrignani (UvA) 26

Figure 10 The ubiquity of PAH emission in the Universe. Starting from the lower left corner and going clockwise: Spitzer composite image of Messier 81, a spiral galaxy like our own Milky Way, where the colour red corresponds to the 8.0 µm emission from PAHs; the iconic star forming region Pillars of Creation in the Eagle Nebula in the 8.0 µm Spitzer filter; the protoplanetary disk around the young star HD 97048 observed in the PAH filter with the Very Large Telescope (VLT); PAH spectrum in three different young stars with protoplanetary disks. The spectral changes implies that chemistry is taking an active role in shaping the PAH population. Image credits: M81, Pillar of Creations: NASA/JPL/Caltech/Harvard-Smithsonian Center for Astrophysics; HD 97048: ESO/C. Moutou. A kick-start for a young researcher Testimonial Dr Annemieke Petrignani “The Dutch Astrochemistry Network (DAN) has been an amazing new experience of doing research for me. It has proven to be a very efficient bottom-up approach into building a network that can yield answers to the key questions in the field. Personally, it was an extremely efficient way for me to easily integrate and make a contribution to the advances made, where the sum was and is by far more than that of the individual efforts.

When I started working for the Leiden Observatory in 2011, I had just switched fields, going from quantum molecular dynamics to astrochemistry. As a newcomer to this field, I did not know many scientists working in astrochemistry and they did not know me. I felt like an ignorant student, fresh from school, having to build up new research and a new network.

This feeling luckily did not last very long. My research project was part of DAN-I; meaning groups at different universities already had set up strong collaborations. This was, and still is, also true for the molecular dynamics group of Jos Oomens (Radboud University), the astrochemistry group of Xander 28 Tielens (Leiden Observatory), and the molecular photonics group of Wybren Jan Buma (University of Amsterdam). As such, I could perform spectroscopy and fragmentation experiments while directly being involved in the impact of the laboratory findings to astrochemical models and theory, and vice versa. For the first time, I was really involved in end-to-end research, with experimental research directly being used and applied to astrochemical models and observations and questions coming back to the lab. It was a perfect combination; I was both the expert and the student.

“It was a perfect combination; I was both the expert and the student.” — Dr Annemieke Petrignani about her start in the Dutch Astrochemistry Network

Lines became even shorter when I was given the opportunity to organise the Lorentz workshop on Interstellar PAHs in 2013 in Leiden together with Xander Tielens and Lou Allamandola (from NASA Ames Research Center). This workshop was strongly instigated by the collaboration between DAN-I and the Carbon in the Galaxy consortium of NASA. Almost instantly – this was at least what it felt like for me – I knew the majority of the people involved in interstellar PAHs and they knew me. I had ‘instantly’ gained access to a world I wasn’t part of before. Main players in the field suddenly were just a call or email away and fruitful collaborations were started. Lou Allamandola himself had become a friend and my youngest daughter still proudly wears the NASA shirt that my oldest daughter was wearing when she (accidently) featured on the background of the workshop screen.

The formation of a strong community was also marked by the beginning of the AstroPAH newsletter. Four other young researchers and I joined forces to set up this newsletter even though we had never worked together and came from different institutes, countries, and/or disciplines. I also had the opportunity to help form and join a supporting community for an Early Release Science proposal for JWST as in 2017, as I was able to co-organise a follow-up meeting on PAH research in the light of James Webb Space Telescope (JWST).

The strong collaborations and the short lines between scientists have resulted in a solid community that I feel very much part of. This consortium now includes a second bottom-up network on planetary and exoplanetary science (PEPSci) – and NASA Goddard, adding contacts in the field of Earth sciences and (astro)biology. I also joined the PEPSci, though only from the sidelines. That is, until the Origins 29 Center came into life. I now am involved in even more exciting new adventures within this centre. The foundation the PEPSci network offered, lead to a chance discussion on a mere perception of an idea changing into an exciting interdisciplinary project that we are currently pursuing.

The respective networks have meant a lot to my research and me. They have paved the way to the exciting Vidi research I’m doing and, recently, to new exciting projects on the origins of and search for life. They have also been the basis for some long-lasting friendships.” Astrochemists of the network Interaction between and coordination of the different science themes is the responsibility of the network Chair: Prof. Xander Tielens (Leiden University). The network Chair is responsible for the overall scientific progress of the network and provides the point of contact to the larger scientific community as well as NWO. In addition, the network Chair is also responsible for the coordination of international activities. The Chair is supported by two thematic coordinators for each of the three themes, one from astronomy and one from chemistry/molecular physics. For The gaseous molecular Universe, the icy Universe and the aromatic Universe these are respectively; Prof. Ewine van Dishoeck and Prof. Gerrit Groenenboom; Prof. Harold Linnartz and Prof. Matthias Bickelhaupt; and Prof. Xander Tielens and Prof. Jos Oomens.

An international board of experts in the field of molecular astrophysics will review the overall functioning of the network and progress towards the goals and objectives of the network every two years. The International Board consist of Dr Timothy Lee (NASA Ames Research Centre, USA), Prof. Tom Millar (Queen’s University, Belfast, UK) and Prof. Stephan Schlemmer (Universität zu Köln, Germany). 31 In the proceeding pages the biographies of the Principal Investigators (PIs) and co-PIs provide an overview of the expertise combined in the network. They are listed in order of their thematic affiliation within DAN-II. Prof. W.M.G. (Wim) Ubachs leads a group at LaserLaB Vrije Universiteit Amsterdam, as well as at the Advanced Research Center for Nanolithography, also at Amsterdam. His work focuses on the spectroscopy of molecules in the gas phase, in a variety of wavelength ranges including the extreme ultraviolet for which he developed narrowband laser sources. The precision spectroscopic work aims at fundamental physics (Physics beyond the Standard Model) and at various applications in astrophysics, 32 astrochemistry and atmospheric physics. In the past decade he has been involved in astronomical observations of molecules, in the optical (at VLT and Keck), and in the radio domain (at Effelsberg, IRAM-30m, ALMA, EVLA) searching for possible variations of fundamental constants of nature. In 2015, prof. Ubachs received an ERC-Advanced grant. He has authored >300 refereed papers, of which 30 in Physical Review Letters, with some 9,000 citations and an h-index of 41. He has been PhD advisor or co-advisor for 35 PhD students. Prof. E.F. (Ewine) van Dishoeck is professor of molecular astrophysics at Leiden Observatory where she leads a group on the physics and chemistry of interstellar molecules, focusing on regions of star and planet formation. She combines observations and models, and has made important contributions to our understanding of the basic molecular processes in space. She is proud to have supervised the theses of more than 40 PhD students. Prof. van Dishoeck is the scientific director of the Netherlands Research School for Astronomy (NOVA), co-PI of the European JWST-MIRI consortium, and president-elect of the 33 International Astronomical Union (IAU), the worldwide organization of professional astronomers. She has received numerous honors and awards, including the Dutch Spinoza award (2000), an ERC Advanced grant (2012), the Dutch Academy Prize Professorship (2012), the Lise Meitner Göteborg award in physics (2014), the Albert Einstein world award for science (2015), and the US James Craig Watson medal (2018). She is a Member of the Dutch, German and US Academies of Sciences. She has more than 550 refereed publications, >35000 citations (ADS) and an h-index of 96. Prof. G.C. (Gerrit) Groenenboom is chair of the Theoretical Chemistry group in Nijmegen. He works on ab initio electronic structure calculations of weakly interacting complexes, radicals, and electronically excited states and he performs quantum dynamical studies of bound states, inelastic- and reactive scattering, photodissociation, and collision induced absorption. He was coordinator of the gas-phase theme in DAN I and is currently coordinator of the gas-phase theme of DAN II. He was a fellow of the Royal Dutch Academy of Science, received two NWO-CW 34 Young Chemist grants, an NWO-CW ECHO grant, two NWO-EW Astrochemistry grants, and he was an associated partner of the EuroQUAM Collaborative Research Project Cold Polar Molecules. He has supervised or co-supervised 10 PhD theses and he authored or co-authored more than 140 refereed publications, including 4 papers in Science and 7 papers in Nature Chemistry and Nature Astronomy and his current h-index is 31. He was the director of the Han-sur-Lesse winter-school on ‘Theory and Spectroscopy’ for 10 years and he was scientific advisor of the Kavli Institute for Theoretical Physics program on Universality in Few-Body Systems. Prof. A. (Ad) van der Avoird became part-time professor of Theoretical Chemistry at the (now Radboud) University in Nijmegen in 1968, while he was also head of the Molecular Physics group at the Unilever Research Laboratory in Vlaardingen. In 1971 he became full professor in Nijmegen and since 2008 he is emeritus. He held visiting professorships at Yeshiva University, New York (1970), at the University of California in Berkeley (1992), and at the University of Bielefeld (1996). In 2007 he received an Alexander von Humboldt Senior Research Award and he regularly worked for shorter periods as a visiting professor at the Fritz Haber Institute of the Max Planck 35 Society in Berlin and at the Technical University Munich. In 1979 he was elected member of the Netherlands Royal Academy of Arts and Sciences and in 1997 of the International Academy of Quantum Molecular Sciences. About 35 Ph.D. degrees were obtained under his supervision and he (co-)authored more than 300 scientific publications. He was in the Editorial Boards of several high-ranked international journals in Physical Chemistry and Chemical Physics. He is still very active in research: in 2018 he already co-authored 1 publication in Nature Astronomy, 3 in Nature Chemistry, 1 in Physical Review Letters and 2 in the Journal of Chemical Physics. Prof. D.H. (David) Parker leads the department of Molecular and Laser Physics at the Institute for Molecules and Materials at the Radboud University Nijmegen. His research concerns the development and application of ultrasensitive detection methods for the study of molecular interactions important in the gas phase and, recently, at gas-surface interfaces. He is most recognized for the invention of the velocity map imaging technique, which is used world-wide as the premier experimental method in physical 36 and chemical research on molecular interactions. In the past 10 years prof. Parker has supervised ~20 PhD thesis focused mainly on photodissociation and inelastic scattering of small molecules important in the Earth atmosphere and – as part of the Dutch Astrochemistry Network – on molecules relevant in astrochemistry. Prof. Parker has co-authored ~250 publications with nearly 8000 citations and a h-index of 42. He has coordinated several large EU networks, is member of the editorial board of the journals Molecular Physics and the Chinese Journal of Chemical Physics, and is a Fellow of the American Physical Society. Prof. S.Y.T. (Bas) van de Meerakker studied physics in Nijmegen. During his PhD at the FOM Institute Rijnhuizen in Nieuwegein (2000-2006), he constructed a new generation Stark decelerator to slow OH radicals to a standstill, and to subsequently load them into an electrostatic trap. He did a short postdoc with David Chandler at Sandia National Laboratories in Livermore, US, where he worked on methods to cool molecules in crossed beam collision experiments. In 2006, he became group leader at the Fritz-Haber-Institute of the Max Planck Society in Berlin, where he set up the first crossed beam scattering experiment using a Stark decelerator. He was awarded a Vidi grant from the Netherlands Organisation for Scientific Research (NWO) and returned to Nijmegen as Assistant Professor in 2011. Here, he set up a new crossed beam experiment using the combination of Stark deceleration and velocity map imaging. In 2013 he was awarded an ERC Starting Grant, which allowed him (together with other NWO grants) to extend his group, and to study molecular collision processes with unprecedented resolution, and at low collision 37 energies where the wave-character of the colliding molecules dominate the interaction. He also developed a new type of Zeeman decelerator, the magnetic analogue of a Stark decelerator, to extend collision experiments to magnetic species like oxygen. In 2016 he was appointed full professor at Radboud University Nijmegen. He has received several prizes and awards for his work. He received the Otto Hahn Medal of the Max Planck Society in 2008. He was appointed guest professor at the University of Bordeaux (2012), and Feinberg Visiting Fellow at the Weizmann Institute in Israel (2014). In 2016 he was elected as JILA Visiting Fellow (Boulder, USA). In 2016 he received the Zdenek Herman Young Scientist Prize of the MOLEC conference, and the Broida Prize of the International Symposium on Free Radicals in 2017. Apart from his scientific work, he was appointed Director of the Radboud Pre-University College of Science in 2017. This College organizes a range of activities for high-school students and their teachers, both on University campus and within high schools, with the goal to establish a better connection between high school education and academia. Prof. M.R. (Michiel) Hogerheijde studies gas and dust in planet-forming disks, often employing high-resolution imaging. In 2005 he started a VIDI-funded research program using millimetre interferometers such as SMA and CARMA. This led to one of the first demonstrations of radial drift of mm-sized grains in a disk. With the Herschel Space Observatory, launched in 2009, he discovered cold water vapour extending across disks, betraying large reservoirs of ice locked up near the midplane. In 2012 he was co-author on the first ALMA publication on planet-forming disks. In 2013 he started a TOP-funded research program using ALMA to study the chemical imprint of the CO snow line in disks. This work has shown that the presence of molecules like DCO+, DCN, N2D+, 38 and H2CO yields critical information on the physical structure of the disk. Hogerheijde has supervised 11 PhD students and a large number of postdocs. He has authored 173 papers, including 20 as lead author. His most cited papers have 100+ citations, and he has an h-index of 49. Hogerheijde has served on the European and international ALMA Science Advisory Committees. He has initiated and led the ALMA Regional Centre node in the Netherlands, Allegro, since 2004. Allegro provides data quality control and user support for ALMA users in the Netherlands. Allegro also develops advanced image calibration methods, provides critical ALMA support for the calibration of high frequency and long baseline ALMA observations, plays a prominent role in mm-VLBI with ALMA, and performs software development for data modelling. In 2017, Hogerheijde was appointed adjunct professor at the University of Amsterdam. Prof. H.V.J. (Harold) Linnartz is the director of the Sackler Laboratory for Astrophysics (www.laboratory- astrophysics.eu) and holds the chair for Laboratory Astrophysics at Leiden Observatory. His research focuses on high resolution spectroscopy and photodynamics of molecular transients of astrochemical interest and the chemical processes taking place in inter/circumstellar ices that lead to the formation of larger complex organic molecules. These are considered to be the building blocks of species that are needed for life. His work allows to interpret and guide astronomical observations and provides the parameters needed for astrochemical models or to compare with theoretical 39 chemical findings. Since his start in Leiden, in 2005, Prof. Linnartz has supervised more than 20 PhD theses. He obtained a Springplank (~Vidi) and Vici grant, ‘to unlock the chemistry of the heavens’ and has been research coordinator of LASSIE, a large European Network focusing on solid state astrochemistry. He currently acts as co-PI on ‘Ice Age’, an early release science program on the James Webb Space Telescope. Prof. Linnartz is board member of several international meetings and scientific journals and coordinates worldwide activities in laboratory astrophysics. He has (co)authored more than 200 peer reviewed publications. Prof. H.M. (Herma) Cuppen is a professor in computational chemistry. Her research focuses on the understanding of mobility in molecular materials, in particular diffusion and chemistry in interstellar ices. She uses a range of different simulation techniques, but is also involved in experimental collaborations. She is known for her work on the microscopic kinetic Monte Carlo 40 technique, which she introduced to astrochemistry, to study the growth of ice layers in detail. Prof. Cuppen was a recipient of an ERC Starting Grant and Vidi grant. Moreover, she is a working group leader to COST action ‘Our Astro-Chemical History’ and she is a member of the IMM board. Prof. Cuppen has authored or co-authored 98 refereed papers with 2,510 citations (Web of Science) and an h-index of 29. Prof. Cuppen has (co)supervised 7 PhD theses. Dr B. (Britta) Redlich leads a group at Radboud University in Nijmegen on Infrared and THz spectroscopy using the FELIX free electron lasers to contribute to the understanding of modifications in interstellar ices and to perform cold ion spectroscopy to fingerprint molecules of interest to astronomy. She obtained her PhD on studies of the adsorption of small molecules on insulating surfaces using infrared spectroscopy from the University of Hannover (Germany) in 1998 and held a postdoctoral position at University of Münster (Germany) studying laser-induced desorption using the Free Electron Laser FELIX at the FOM Institute Rijnhuizen, 41 Nieuwegein, NL. She received an Emmy-Noether fellowship from the Deutsche Forschungsgemeinschaft (DFG) to continue this project at FOM Rijnhuizen. In 2003 she became FELIX Facility Manager and has been responsible for the user program and operation of the FELIX laser. In 2013 the FELIX lasers have been relocated to the Radboud University in Nijmegen and currently she is the director of the FELIX Laboratory. She has co-authored 65 peer reviewed papers and has an h-index of 19. She is member of the general assembly of LEAPS, LaserLab Europe, CALIPSOplus and the steering committee of FELs of Europe. Prof. W.J. (Wybren Jan) Buma holds the chair of Molecular Spectroscopy at the University of Amsterdam and the special chair in Spectroscopy of Photoactive Molecules and Materials at the Radboud University. He is also the Scientific Director of the Holland Research School of Molecular Chemistry (HRSMC). His research aims to advance the fundamental knowledge of the dynamics of excited states in molecules and nanosized objects, and to contribute with its expertise to applications of the photosciences. Another line of research focusses on the development of novel 42 spectroscopic techniques for analytical applications. Over the past years, his group has made a substantial contribution to the field of high-resolution spectroscopy of large, complex molecular systems. Prof. Buma has (co)supervised 19 PhD theses. He has been Coordinator of EC-funded Networks (Training and Mobility of Researchers (TMR), Marie Curie Training Site (2001-2004), and Specific Targeted Research or Innovation Project). He has authored 175 refereed papers (h-index 29). He was member of the SynNanoMotors team that was awarded the 2008 EU Descartes Prize for Transnational Research. Dr A.M. (Anouk) Rijs is an assistant professor in (bio)physical chemistry within the FELIX IR free electron laser Laboratory of the Radboud University (Nijmegen, the Netherlands). She is an expert on (far)-IR action spectroscopy combined with mass spectrometry for the structural characterization and conformation dynamics of biomolecules such as peptides and carbohydrates. Recently, the Rijs group has advanced a research program on the chemistry of PAH formation and the characterization of PAHs in the mid- and far-IR. For her development of far-IR and THz spectroscopy applied to biomolecules, she received the FOM Minerva award as well as the Mildred Dresselhaus Guest Professor at The Hamburg Centre for Ultrafast imaging (CFEL, Max Planck for Structure and 43 Dynamics/Universität Hamburg, Germany). Her expertise in this area is evidenced by her excellent publication output; over 50 international peer-review journals as well as 10+ invited/keynote/ plenary lectures at international conferences in the 2017-2018. In addition to her work at Radboud University, she is leading editor and one of the authors of the book ‘Gas-Phase IR Spectroscopy and Structure of Biological Molecules’ (Springer), co-chair of the International Symposium on Molecular Beams (ISMB2017), chair of the conference on Isolated Biomolecules and Biomolecular Interactions (IBBI2018) and Associate Editor and member of the editorial board at Physical Chemistry Chemical Physics (PCCP) of the Royal Society of Chemistry. Prof. F.M. (Matthias) Bickelhaupt is chair and head of the Department of Theoretical Chemistry of Vrije Universiteit Amsterdam and holds an extraordinary chair in Theoretical Organic Chemistry at Radboud University Nijmegen. He is known for his developments in the analysis and theory of the chemical bond and methods for rationally designing molecules, nano-structures and materials as well as chemical processes toward these compounds, based on quantum mechanics and advanced computer simulations. Bickelhaupt’s research profile comprises four main directions of research that are intimately connected and of relevance for problems in astrochemistry and (exo)planetary sciences: (i.) Structure and chemical bonding in Kohn-Sham density 44 functional theory, (ii.) DNA replication, (iii.) Elementary chemical reactions, and (iv.) Rational, fragment-oriented catalyst design. With 286 published papers, over 17,000 citations and an h-index of 59, Bickelhaupt held an E.U. visiting professorship at Warsaw University of Technology (2013), was elected member of the Royal Holland Society of Sciences and Humanities (KHMW, 2014), Fellow of the Royal Society of Chemistry (FRSC, 2014), and member of the Advanced Research Center – Chemical Building Blocks Consortium (ARC CBBC, 2016). Among the academic offices he holds, are editorial board memberships of various international journals, among which Chem. Eur. J., chairman of the Holland Research School of Molecular Chemistry (HRSMC), and member of the Round Table Chemistry of the Netherlands Organisation of Scientific Research. Dr I. (Ingmar) Swart is an assistant professor of chemistry and physics at Utrecht University. His research focuses on chemistry at the single molecule level. He made important contributions to the development of atomic resolution imaging of molecules on surfaces with atomic force microscopy. Since his appointment at Utrecht University in 2012, Ingmar Swart supervised 45 4 PhD theses. He is a member of the Dutch Astrochemistry Network II. In 2011, Dr Swart received a Veni grant from NWO. Dr Swart has authored or co-authored 41 refereed papers with in excess of 2,300 citations, including 17 papers with more than 50 citations. His h- and i10-indices are 25 and 34, respectively. He has given five invited talks in the last three years. Prof. J. (Jos) Oomens leads a group in Molecular Structure and Dynamics embedded within the FELIX Laboratory of Radboud University in Nijmegen. Using the IR free electron laser, he developed a method to record IR spectra of ionized molecules in the gas phase. Polycyclic Aromatic Hydrocarbon (PAH) molecular ions were among the first species investigated with this new method, which was of particular relevance for the ‘PAH hypothesis’ and the astronomical UIR emission bands. The method is now also employed to study the gas-phase chemistry of ionized PAHs and more broadly 46 for applications in ion chemistry, biochemistry and analytical chemistry. Within the Dutch Astrochemistry Network, he is the coordinator of the Aromatic Universe theme and he is partner in the EuroPAH European Union ITN network. In 2011, Oomens received an NWO Vici grant for his work involving ion spectroscopy to investigate the dissociation reactions underlying peptide and protein sequencing. He has co-authored well over 300 peer-reviewed articles and has an h-index of 45. He was one of the editors of the book ‘Gas-phase IR Spectroscopy and Structure of Biological Molecules (Springer, 2015). Prof. A.G.G.M. (Xander) Tielens leads a group at Leiden Observatory on the origin, evolution, and role of large PAH molecules in the Universe. He was among the first to recognize the importance of such large molecules in space. He has also made important contributions to the study of interstellar ices, interstellar grain surface chemistry, processing of interstellar dust, and the physics and chemistry of gas in photodissociation regions. Over the past 10 years, prof. Tielens has supervised 14 PhD theses. He is the coordinator of the Dutch Astrochemistry Network. He is the Editor in Chief of the scientific journal, Molecular Astrophysics, Elsevier. He was the Project Scientist of HIFI, the heterodyne instrument on board of the Herschel Space Observatory (1997-2013), 47 the NASA Project Scientist of the Stratospheric Observatory for Infrared Astronomy (SOFIA) (2005-2007), and Coordinator of The Molecular Universe, a Marie Curie Research and Training Network funded under the European Commission Framework Program #6 (2004-2008). In 2012, prof. Tielens received the Spinoza Prize, the highest Dutch scientific award. Prof. Tielens has authored or co-authored >450 refereed papers with in excess of 35,000 citations (ADS), including 30 papers with more than 250 citations and an h-index of 106. He is the author of the textbook ‘Physics and Chemistry of the Interstellar Medium’ (Cambridge University Press), and editor of 5 conference proceedings. He has given 19 invited reviews over the last 10 years. Dr A. (Annemieke) Petrignani leads a research team at the University of Amsterdam on astro-molecular spectroscopy and -chemistry with an emphasis on the (photo) dynamics and signatures of hydrocarbons in space. She focuses on the infrared and optical behaviour as well as on the photo physics of species in ionic and neutral forms using molecular-beam setups and ion traps. Dr Petrignani has supervised multiple students of various levels, co-supervised 3 PhD theses, and (co-)authored over 35 refereed papers. In 2014, she received a NWO Vidi grant to investigate the shapes and sizes of hydrocarbons in space using high-resolution and high-sensitivity spectroscopic techniques. She is the editor of the AstroPAH newsletter. She did her PhD work at the 48 FOM Institute AMOLF performing experiments at the ion storage ring CRYRING in Stockholm investigating the molecular physics of planetary airglow. She was a postdoctoral researcher at the Max-Planck Institute for Nuclear Physics where she investigated the electron recombination and the spectroscopy of molecular ions of astrochemical interest using the TSR storage ring and a 22-pole trap. She worked for the Leiden Observatory at the FELIX Laboratory in Nijmegen to investigate the fragmentation of aromatic hydrocarbons using the free electron laser FELICE. Her current research takes place at both the UvA and the FELIX Laboratory. Colophon

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April 2018

Dutch Astrochemistry Network – II

Netherlands Organisation for Scientific Research