HFML-FELIX user meeting / EPSRC UK users of FELIX workshop

8 Jul 2025, 00:30 → 10 Jul 2025, 23:40 Europe/Amsterdam

HG00.304 (Huygens)

Elvina Dilmieva (HFML), Joost Bakker (Radboud University), Piero Ferrari (HFML-FELIX)

From 8th to 10th July 2025 the FELIX-HFML User Workshop will take place. This is the biennial meeting for researchers using the intense infrared and terahertz FELIX free-electron lasers and high-field magnets. 
This year’s event will also host the 2025 EPSRC-sponsored UK Users of FELIX workshop, a dedicated session for existing and prospective UK users to explore new opportunities for FELIX-based research.

Booklet HFML-FELIX User meeting.pdf

Conference pictures

• IMG_20250709_160622_682.jpg
• IMG_20250709_160622_745.jpg
• IMG_20250709_160623_072.jpg
• Thanks.pptx

Tuesday 8 July

Arrival & Registration

Lunch

Oral sessions: Tuesday PM-1

1 Welcome - HFML-FELIX as a national institute

Speaker: Jos Oomens (HMFL-FELIX)

2 Technical installations of HFML-FELIX, an update and outlook

In this short contribution, we will briefly describe the general characteristics of our free-electron lasers and magnet installations. We will also address recent upgrades of the infrastructure, such as the replacement of the FEL modulator in January 2025 or the start of cooldown of the hybrid magnet aimed to operate at 45 T.

Speakers: Wouter Stumpel (HMFL-FELIX), Andries den Ouden (HFML-FELIX)

3 IR spectroscopy of ionized endohedral fullerenes

Fullerenes, in both neutral and ionized forms, are the largest molecular species identified in the interstellar medium. Among their many derivatives, ionized species—including protonated, oxidized, and other exohedral variants— have attracted considerable astrophysical interest. Recent advances in synthesis methods have enabled the encapsulation of small molecules within fullerene cages, making the spectroscopic investigation of ionized endohedral fullerenes possible.

We present the gas-phase experimental vibrational spectra of H2O@C60 in its protonated and radical cationic forms. The spectra of the ionized endohedral fullerenes are compared to the vibrational spectra of C60H+ and C60+. We found that the vibrational spectra of the ionized fullerenes are almost entirely identical to their endohedral versions. The phenomenon is likely due to a shielding effect, where the polarization of the fullerene cage reduces the dipole moment of the whole system, thereby suppressing the IR intensities associated with the vibrational modes of the encapsulated water molecule.

Consequently, ionized endohedral fullerenes have the same astrophysical signatures as the ionized fullerenes they derive from, making them potentially indistinguishable in spectra detected from the interstellar medium.

Speaker: Julianna Palotas (University of Edinburgh)

Coffee break

Oral sessions: Tuesday PM-2

4 Using FELIX to Investigate IR Photon Induced Desorption From Astrophysically Relevant Ice Surfaces

Ice-covered dust grains are found in many astrophysically relevant environments, including comets, proto-planetary disks and the interstellar medium, and provide surfaces upon which many of the molecules found in space can be made. These ice-covered dust grains undergo so called processing by bombardment with particles such as atoms and ions, by irradiation with light and by heating (thermal processing). Processing leads to the release of species from the icy surface into the gas phase, where they can undergo reaction to form other molecules, and also to chemical reactions that can lead to the production of complex, pre-biotic, species.
We have undertaken a detailed study of the infrared photodesorption of astrophysically relevant molecules using high intensity, tuneable, infrared light from FEL-2 at FELIX. Irradiated ices consisted of CO or N2 mixed with amorphous H2O ice, adsorbed on a cryogenically cooled (9 K) metallic substrate surface. Isotope effects were also investigated using 13CO and D2O in place of the 12CO and H2O ice. Ices were irradiated with light in the mid-IR range from 2.8 – 16 µm, at wavelengths corresponding to the vibrational modes of the H2O/D2O and 12CO/13CO or N2 vibrational modes. Changes in the ices were monitored using a combination of pre- and post-irradiation reflection absorption infrared spectroscopy to monitor changes in the ice morphology, and photon induced desorption using a quadrupole mass spectrometer, to measure desorption during irradiation.
Studies show that CO and N2 desorb from the mixed ices, following irradiation at wavelengths corresponding to the H2O/D2O vibrational modes. These results show that a number of different desorption channels exist on these icy surfaces, and also demonstrate that infrared induced desorption should be included in astrophysical models of ices on dust grain surfaces.

Speaker: Wendy Brown (University of Sussex, UK)

5 IR spectroscopy in high magnetic fields: Performing combination experiments at HFML-FELIX

The abstract for my talk can be found in the attachment.

Speaker: Dr Maurice Bal (HFML-FELIX)

6 Cryogenic IR Spectroscopy of the Hydrogen-Bonded Phosphoric Acid Dimer

Phosphates are ubiquitous in nature and play a crucial role in biochemical processes such as protein synthesis, metabolism, and energy production. One unique property of phosphoric acid is that it exhibits the highest intrinsic proton conductivity of any known substance and is used in low-temperature batteries as well as in phosphoric acid fuel cells (PAFCs). The detailed mechanism of proton transport, however, is not yet fully understood.
In this study, we examine the mass-selected deprotonated dimer of phosphoric acid in the gas phase using infrared action spectroscopy in helium nanodroplets, employing tunable infrared photons from the Free-Electron Laser at the Fritz Haber Institute (FHI-FEL). This technique enables the acquisition of spectra at a cryogenic temperature of 0.37 K, reducing spectral congestion and yielding well-resolved vibrational bands. Studying hydrogen-bonded systems at these temperatures provides unique insights into their fundamental properties, enhancing our understanding of phosphoric acid chemistry and its interactions across various environments. Our investigation reveals molecular structures that can serve as calibration points for quantum chemistry calculations. The elucidation of experimental vibrational bands, hydrogen-bond interactions between the two moieties, and associated spectroscopic details will be discussed.

Speaker: América Torres Boy

Posters

Wednesday 9 July

Oral sessions: Wednesday AM-1

7 Spectroscopic studies of cold, trapped anions in radiofrequency multipole traps

Speaker: Kartrin Dulitz (Universität Innsbruck)

8 Isomer-selective formation methods of astrochemical ions characterized by IR action spectroscopy

The study of gas-phase ion-neutral reactions is a subject of significant research interest for astrochemistry, due to their higher reaction rates at low temperatures and pressures than the equivalent neutral-neutral processes [1]. Furthermore, following recent increases in observational capabilities, a growing appreciation has developed regarding the importance of isomers in astrochemistry [2,3], with the low-temperature conditions in many environments making barriers to interconversion inaccessible. This means that the relative densities of different isomers can deviate significantly from what would be predicted by a thermochemical equilibrium, instead reflecting the relative rates of formation and destruction. As a result, to accurately reproduce the chemistry of these astrochemical environments, modelers require isomer-specific experimental data.

While some isomeric species can be synthesized selectively, allowing isomeric ions to be generated through direct ionization of the isomer-specific neutral samples, many relevant ionic isomers lack stable neutral equivalents, and so alternative methods must be developed. One particularly promising approach to this has been the use of dissociative ionization processes [4,5], where larger neutral molecules are ionized into excited states that can then dissociate into the ionic isomer of interest along with a corresponding neutral fragment or fragments, with the target ion typically being selected based on their mass-to-charge (m/z) ratio. However, this doesn’t allow for any discrimination against isobaric ions, including other isomers that can result from structural rearrangement prior to fragmentation. Spectroscopic measurements are therefore needed for structural identification of the ions formed by such processes.

Sulphur is among the ten most abundant elements in astrochemical environments, and S-containing species have been detected in environments ranging from photodissociation regions and protoplanetary disks to dense cores and exoplanetary atmospheres [6-8]. An environment where a diverse range of S-containing species have been detected is the carbon-rich cold, dark cloud TMC-1, with the recent observation of HCCS+ marking the first observation of a protonated radical species in a cold dark cloud [9]. While the H2CCS•+ ion has not yet been observed, HCCS neutral has been [10], with the protonation of HCCS to give H2CCS•+ potentially proceeding similarly to the protonation of CCS, which is believed to be the major pathway for HCCS+ formation in TMC-1 [9]. Importantly, extremely limited experimental data for both HCCS+ and H2CCS•+ is currently available, largely due to a lack of known generation methods for either species [11].

In these studies, we have identified methods for the selective generation of both HCCS+ and H2CCS•+, using 2,5-dibromothiophene and thiophene, respectively. These formation methods have been probed through both computational potential energy surface (PES) calculations and experimental vibrational spectroscopy. Experimental measurements utilised the FELion instrument [12], in conjunction with the FELIX beamline [13], to perform infrared pre-dissociation (IR-PD) spectroscopy of the ions formed by dissociative ionization. Comparison of these experimental spectra with theoretical predictions and the calculated fragmentation PESs allows us to conclusively identify the fragment ions as the target species.

These results not only expand our understanding of fragmentation dynamics but enable future reactivity measurements of these ions. These measurements also provide vibrational spectra that can be used as the basis for future observations, in particular by the vibrational spectrometer of the James Webb Space Telescope.

References
[1] M. Larsson, W. D. Geppert, and G. Nyman, “Ion Chemistry in Space”, Reports on Progress in Physics, 75, 066901 (2012)
[2] M. A. Cordiner, N. A. Teanby et al. “ALMA Spectral Imaging of Titan Contemporaneous with Cassini’s Grand Finale”, The Astronomical Journal, 158, 76 (2019)
[3] R. C. Woods, C. S. Gudeman et al. “The [HCO+]/[HOC+] abundance ratio in molecular clouds”, The Astrophysical Journal, 270, 583-588 (1983)
[4] V. Richardson, C. Alcaraz et al. “The reactivity of methanimine radical cation (H2CNH•+) and its isomer aminomethylene (HCNH2•+) with methane”, Chem. Phys. Lett., 775, 138611 (2021)
[5] V. Richardson, L. Alcock et al. “Experimental Characterization of the Isomer-Selective Generation of the Astrochemically Relevant Hydroxymethylene Radical Cation (HCOH•+/DCOH•+)”, J. Phys. Chem. Lett., 15, 10888-10895 (2024)
[6] J . R. Goicoechea, J. Pety et al. “Low sulfur depletion in the Horsehead PDR”, A&A, 456, 565-580 (2006)
[7] C. Vastel, D. Quénard et al. “Sulphur chemistry in the L1544 pre-stellar core”, Monthly Notices of the Royal Astronomical Society, 478, 5514-5532 (2018)
[8] R. Le Gal, K. I. Öberg et al. “Sulfur Chemistry in Protoplanetary Disks: CS and H2CS”, The Astrophysical Journal, 876, 72 (2019)
[9] C. Cabezas, M. Agúndez et al. “Discovery of the elusive thioketenylium, HCCS+, in TMC-1”, A&A, 657, L4 (2022)
[10] J. Cernicharo, C. Cabezas et al. “TMC-1, the starless core sulfur factory: Discovery of NCS, HCCS, H2CCS, H2CCCS, and C4S and detection of C5S”, A&A, 648, L3 (2021)
[11] T. J. Millar, C. Walsh et al. “The UMIST Database for Astrochemistry 2022”, A&A, 682, A109 (2024)
[12] P. Jusko, S. Brünken et al. “The FELion cryogenic ion trap beam line at the FELIX free-electron laser laboratory: Infrared signatures of primary alcohol cations” Faraday Discuss. 217, 172-202 (2019)
[13] D. Oepts, A. F. G. Van der Meer, and P. W. Van Amersfoort, “The free-electron-laser user facility FELIX”, Infrared Phys. Technol. 36, 297-308 (1995)
[14] J. A. Diprose, K. Steenbakkers et al. “Selective formation and spectroscopic characterization of the H2CCS•+ radical cation via dissociative ionization of thiophene” J. Chem. Phys. 162, 164304 (2025)

Speaker: Vincent Richardson (Department of Physics, University of Liverpool)

9 Catalysis meets Astrochemistry: Ultra-Small Magnesium-Silicates in the Gas-Phase

Magnesium-silicates are ubiquitously found as small dust grains throughout the interstellar medium (ISM). Formed in the dense and warm environments of dying (evolved) oxygen-rich stars, they are subject to sporadic energetic processing in the diffuse ISM, where they are broken up into ultra-small silicate fragments. Such fragments likely serve as seeds for subsequent re-condensation in dense interstellar clouds but might also be highly relevant catalyst for the activation and conversion of small molecules into complex organic molecules (COMs).
In our work, we apply experimental and theoretical methods, that are well established in cluster catalysis research, to study fundamental problems of silicate dust related astrochemistry: infrared multiple-photon dissociation (IR-MPD) spectroscopy combined with ion trap and flow tube reaction studies and density functional theory (DFT) computations. With this approach we aim to gain insight into the geometric structure of ultra-small silica and silicate fragments, their potential growth through oxygen1 and/or dissociative water adsorption2 as well as their reactive and catalytic properties, especially with respect to the activation and conversion of CO2. In addition, silicate-based dust particles are likely also the origin of meteoric smoke particles (MSP) that result from dust impacting on the upper atmosphere and are thus probably involved in the formation of mesospheric ice-based noctilucent clouds (NLC). We show that highly oxidized anionic silicate clusters exhibit all the necessary chemical, electronic and optical properties to be highly credible candidates for such MSP-based NLC nucleation seeds.3 Besides structural and mechanistic studies we also aim to provide infrared spectroscopic reference data for the potential identification of such clusters in the interstellar medium (ISM) by the James Webb Space Telescope.

[1] J. Mariñoso Guiu, B.-A. Ghejan, T.M. Bernhardt, J.M. Bakker, S.M. Lang, S.T. Bromley, ACS Earth Space Chem. 6 (2022) 2465
[2] A.A. de Donato, B.-A. Ghejan, J.M. Bakker, T.M. Bernhardt, S.T. Bromley, S.M. Lang, ACS Earth Space Chem. 8 (2024) 1154
[3] J. Mariñoso Guiu, J.M. Bakker, T.M. Bernhardt, J.M.C. Plane, S.T. Bromley, S.M. Lang, npj Clim. Atmos. Sci. 8 (2025) 153

Speaker: Sandra Lang (Ulm University)

10 IR-FEL Investigation of NO activation on Cobalt Clusters

Please find attached my abstract for an oral presentation

Speaker: Peter Rubli (Department of Chemistry, University of Oxford)

Coffee break

Oral sessions: Wednesday AM-2

11 Orbital FF/LO Phases in NbSe2 Multilayers

Recent advances in two-dimensional materials have opened new avenues for exploring unconventional superconductivity in engineered multilayers. Among them, transition metal dichalcogenides (TMDs), such as NbSe2, offer a unique platform to investigate Ising superconductivity and quantum phase transitions under strong spin-orbit coupling. In this talk, I will show Fulde-Ferrell-Larkin-Ovchinnikov FFLO state arises from Josephson coupling between adjacent superconducting layers, enabling the formation of finite-momentum pairing states. I will present evidence for identifying orbital Fulde–Ferrell (FF) and Larkin–Ovchinnikov (LO) states in multilayer NbSe2, where field-tunable inversion symmetry breaking emerges spontaneously within a globally centrosymmetric system. These FF/LO phases exhibit distinctive features such as nonreciprocal transport, Berezinskii–Kosterlitz–Thouless (BKT) criticality near phase boundaries, and strongly anisotropic I–V characteristics. Our findings reveal that inversion symmetry breaking can be a dynamic and emergent property of finite-momentum condensates, offering a new pathway to polar superconductivity and exotic collective behavior in 2D quantum systems.

Speaker: Jianting Ye (University of Groningen)

12 Interaction of infrared free electron lasers with metasurfaces: present status and future directions

The interaction of light with metasurfaces, two-dimensional arrays of subwavelength-spaced nanostructures, or "meta-atoms", paves the way for the advanced study of their optical properties. Metasurfaces can be meticulously designed to introduce desired localized and spatially varying electromagnetic responses, thereby collectively imparting arbitrary phase, amplitude, and polarization transformations upon an incident wavefront. The fundamental principle hinges on the resonant coupling of incident light with the meta-atoms, which can be precisely tailored by controlling their geometry, material composition, and arrangement. Consequently, by systematically measuring the far-field optical response—such as the intensity and polarization state of transmitted, reflected, or scattered light—one can retrieve the effective optical parameters of the metasurface. This characterization process enables the direct quantification of key performance metrics, including polarization conversion efficiency, phase modulation depth, and operational bandwidth, thereby providing critical insights into the underlying light-matter interactions that govern the metasurface's functionality. These interactions are often studied by conventional benchtop lasers, while the interaction of Free-Electron Lasers (FELs) with metasurfaces is a cutting-edge field driven by the unique properties of FELs (high intensity, ultrashort pulses, broad tunability, and spatial coherence) and the unprecedented light control offered by metasurfaces. However, the ability of FELs to probe metasurfaces is so far limited to pump-probe spectroscopies, which are informative but do not exploit their potential in full. In this presentation, the interaction of FELs with metasurfaces is revisited from a comparison point of view with their counterpart, conventional benchtop lasers. The extraordinary ability of FELs to study metasurfaces is discussed, which can be used as a guideline by researchers in the field of metamaterials and nanophotonics. Finally, some of our recent results on investigating the plasmonic metasurfaces using Free Electron Lasers for Infrared eXperiments (FELIX) are discussed. In this investigation, we studied how the geometrical features of plasmonic metasurfaces will affect the dynamic optical response using time-resolved pump-probe spectroscopy. The transient transmission change was measured for plasmonic metasurfaces with different plasmonic resonances, emphasizing the crucial role of resonance position.

Speaker: Amirmostafa Amirjani (Quantum Solid-State Physics, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200d, 3001, Leuven, Belgium)

13 Sum- Frequency Generation Spectro-Microscopy using the FHI-FEL

Speaker: Dorothee Mader (Fritz-Haber-Institut)

HFML_FELIX_User_Meeting_Abstract_Mader.pdf

Lunch

Oral sessions: Wednesday PM-1

14 Controlling order with light

see attached file

Speaker: Michael Först

15 Fractional Quantum Hall Experiments on Twisted Graphene and Parton-Based Topological States

We report experimental measurements of the fractional quantum Hall effect (FQHE) in twisted graphene aligned with hexagonal boron nitride, where the formation of a moiré superlattice and sublattice symmetry breaking gives rise to a rich landscape of correlated electronic phases We report on the FQHE at filling factors ν = k/2 and ν = k/3 with ν > 1, and on the composite fermions at in the ν < 1 lowest landau Level, including ν = 4/5, 5/7 and 2/3. These fractional states can be described with a partons model, in which the electron is broken down into sub-particles each one residing in an integer quantum Hall effect state; partons are fictitious particles that, glued back together, recover the physical electrons. This model captures the observed hierarchy of FQHE states and describes the existence of exotic anyons with Abelian and non-Abelian statistics. Our results reveal the power of combining band structure engineering with strong correlations to stabilize unconventional quantum Hall states, offering new avenues for exploring topological phases of matter.

J. Salvador-Sánchez, A. Pérez-Rodriguez, V. Clericò, O. Zheliuk, U. Zeitler, K. Watanabe, T. Taniguchi, E. Diez, M. Amado and V. Bellani, "Composite fermions and parton wavefunctions in twisted graphene on hexagonal boron nitride", Eur. Phys. J. Plus 139, 979 (2024).

Speaker: Vittorio Bellani (Department of Physics "A. Volta", University of Pavia, 27100 Pavia, Italy)

16 Ultrafast all-optical modulation with strongly coupled mid-IR plasmonic metasurfaces

The rapid evolution of photonics has enabled unprecedented control over light-matter interactions on the picosecond time scale and even faster, with plasmonic metasurfaces (MSs) emerging as key components in next-generation optoelectronic devices. MSs composed of periodic gold nanostructures patterned on silicon substrates can offer both localized surface plasmon resonance (LSPR) and all-optical control. While the LSPR amplifies the light-matter interaction1, the silicon substrate facilitates rapid modulation of optical properties through field-enhanced impact ionization. Accelerated free carriers boost the generation of electron-hole pairs and dynamically alter the material’s optical response.2
When irradiated with intense mid-infrared pulses from a free-electron laser (FELIX), the carrier concentration in silicon undergoes significant changes, which can be tracked using time-resolved pump-probe spectroscopy. By modifying the configuration of MSs, namely single-type and coupled-type (Fig. 1), different mechanisms are excited, revealing the interplay between local field enhancement, carrier dynamics, and electromagnetic near-field coupling. These insights uncover novel pathways for ultrafast energy transfer in coupled plasmonic systems, offering a foundation for actively tunable resonant metasurfaces and the development of ultrafast all-optical technologies.

Speaker: The Linh Pham (KU Leuven)

Coffee break

Oral sessions: Wednesday PM-2

17 IRMPD spectra of [Fe,O,H]$^+$, [Fe,2O,H]$^+$, and [Fe,2O,2H]$^+$ in the 110-2000 cm$^{–1}$ spectral range

Transition metals play a role in astrochemistry, in particular, transition metal complexes are proposed to be astrochemically relevant. Iron is the most abundant transition metal in the interstellar medium (ISM), but only little amounts of pure atomic iron are present.[1] The oxide-hydroxide species [Fe,xO,yH]+, and especially [FeOH]+, are potential iron compounds in the ISM, but spectroscopic data for their identification is not available.
We investigate the structure and properties of three iron oxide-hydroxide cations using infrared multiple photon dissociation (IRMPD) spectroscopy. The experiments are performed using a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer (FT-ICR-MS) at the intra-cavity beam line FELICE of the Free Electron Laser (FEL).[2] We recorded the [Fe,O,H]+, [Fe,2O,H]+, and [Fe,2O,2H]+ spectra in the range from 110 cm–1 to 2000 cm–1. The intense light of the FELICE beam line allows for tag-free spectroscopy of those strongly bound systems. Tag-free spectroscopy is important for comparability with ISM data, as tags influence the spectrum.[3] Several characteristic bands are observed for [Fe,O,H]+, [Fe,2O,H]+, and [Fe,2O,2H]+ species that allow for structural assignments. Rotational substructure is observed in many vibrational modes. The infrared spectra are analyzed with high-level computational chemistry calculations and simulation of rotational structures for obtaining the best match of the band structures.

References
[1] N. Cox, “Allen's Astrophysical Quantities,” Springer New York, 2000.
[2] F. J. Wensink, M. G. Münst, J. Heller; M. Ončák, J. M. Bakker, C. van der Linde, “IR multiple photon dissociation spectroscopy of MO2+ (M = V, Nb, Ta),” J. Chem. Phys. 153, 171101 (2020).
[3] S. Jin, J. Heller, C. van der Linde, M. Ončák, M. K. Beyer, “Toward Detection of FeH+ in the Interstellar Medium: Infrared Multiple Photon Dissociation Spectroscopy of Ar2FeH+,” J. Phys. Chem. Lett. 13, 5867–5872 (2022).

Speaker: Christian van der Linde (Universität Innsbruck, Institut für Ionenphysik und Angewandte Physik)

18 Visualizing and Identifying Metabolites using Mass Spectrometry Imaging and IR Ion Spectroscopy

Speaker: Jelle Schuurman

04-07-2025 - HFML-FELIX User Meeting - Jelle Schuurman.docx

19 Integrated Electrochemistry and Mass Spectrometry for Molecular Insights into Electrochemical Reactions

Understanding the mechanisms of electrochemical reactions is essential for numerous applications, including the development of efficient electrocatalysts, redox flow batteries, and electrosynthesis processes. Traditional techniques like voltammetry and bulk electrolysis, while useful, offer limited molecular-level insights into these reactions. As a result, complementary spectroscopic methods are often needed to fully elucidate the mechanisms of electrocatalytic reactions at the molecular level.
Online coupling of electrospray mass spectrometric technique to the electrochemical methods provides a unique strategy in achieving the detailed molecular-level perspective in electrochemical reactions. During the presentation, I will show the key features that make electrochemistry-electrospray ionization mass spectrometry (EC-ESI-MS) a powerful technique for studying electrochemical reactions.[2] These include: transferring reaction intermediates from solution to the gas phase, which eliminates solution-phase interference and enables the detection of short-lived species, utilizing established mass spectrometric methods for complete characterization of intermediates; and allowing simultaneous monitoring of multiple interacting pathways in electrochemical reactions. I will focus on specific examples, such as the electrocatalytic reduction of CO2 and O2,[1] where EC-ESI-MS was instrumental in identifying reaction intermediates, tracking catalyst activation-deactivation, and observing changes to the catalyst itself during the reactions.

Speaker: Abhinav Bairagi (Radboud University)

Lab tours HFML-FELIX

Conference dinner

Thursday 10 July

Oral sessions: Thursday AM-1

20 IR-MPD Studies of Molecular Activation at Metal Clusters

Please find attached abstract for oral presentation (invited).

Speaker: Christian Haakansson (Department of Chemistry, University of Oxford)

21 Vibrational spectra of singly and doubly hydrated TaO$_2^+$ cations

Transition metals and their oxides are relevant for fields like materials science or biochemistry, and have manifold industrial applications. They can serve as catalysts for water activation as an early step in the formation of molecular hydrogen [1]. Tantalum is a third row transition metal and in the past a variety of studies were performed on reactions involving water [2]. In order to be able to study these properties the systems are often simplified by going to small gas phase clusters and the method of argon tagging in combination with infrared spectroscopy is used to determine the structures formed in the reactions. However, using the intracavity free electron laser FELICE at the HFML-FELIX institute allows for the study of bare clusters by infrared multiple photon dissociation (IRMPD) without having to rely on an additional tag. In the present study, water activation on TaO$_2^+$ cations has been studied in the region of 350 cm$^{-1}$ - 1600 cm$^{-1}$. Additionally, quantum chemical calculations were performed using chemical reasonable structures as a starting point. Comparing the experimental spectra with the theoretical frequencies and intensities leads to the conclusion that for both the singly and doubly hydrated cations the hydroxide species are formed. The calculated potential energy surfaces, where TaO(OH)$_2^+$ and Ta(OH)$_4^+$ are the lowest lying minima, are consistent with this assignment. All results are in good agreement with the work of Wang et al. [3], who performed IRMPD of the O-H stretching modes.

Speaker: Sarah Madlener (Universität Innsbruck, Institut für Ionenphysik und Angewandte Physik)

22 Gas phase fullerene-metal complexes as reaction models

Metal clusters in the gas phase exhibit unique properties, such as size dependent reactivities. Those can be studied with mass spectrometry and laser spectroscopy. Along with direct comparison with quantum chemical calculation modelling, metal clusters excellent model systems for investigating chemical reactions and catalytic processes taking place at low-coordinated sites. Previous studies have demonstrated the novelty of reaction model systems. For example, the reactivities of CaMn3O4+ and CaMn4O5+ towards water molecules have been explored as the reaction models for oxygen-evolving complex in photosystem II.1, 2 To gain a comprehensive understanding of reaction mechanisms at the molecular level, it is essential to understand not only the role of active centers but also of the support. Carbonaceous-support metals are of interest in catalysis, hydrogen storage, and related fields. To establish reaction models for such systems, fullerene, serving as gas phase model systems for sp2-bound carbon materials, can be used. The reactivities of metal-fullerene complexes toward small molecules such as H2, H2O, CO2, were systematically investigated.3, 4 These studies have revealed that C60 can promote reaction processes such as water splitting and CO2 reduction. Furthermore, infrared multiple photon dissociation (IRMPD) spectroscopy was employed to examine the vibrational spectra of these complexes. The structures of fullerene-metal complexes and binding motifs of the adsorbates can be identified. Possible reaction pathways were elucidated through theoretical calculations, offering atomic-level insights into the reaction mechanisms.3–6

References
[1] S. Mauthe et al. Angew. Chem. Int. Ed. 131, 8592–8597 (2019).
[2] Y. Zhang et al. Chem. Commun., 55, 14327–14330 (2019).
[3] J. Vanbuel et al. ChemPhysChem 21, 1012–1018 (2020).
[4] G. Hou et al. Angew. Chem. Int. Ed. 60, 27095–27101 (2021).
[5] E. German et al. Carbon 197, 535–543 (2022).
[6] J. Xu et al. J. Am. Chem. Soc. 145, 22243−22251 (2023).

Speaker: Yufei Zhang (KU Leuven)

23 IR characterization of phenanthrene clusters and phenylsilane discharge products as potential astrochemical inventory

Speaker: Melanie Schnell

Coffee break

Oral sessions: Thursday AM-2

24 Molecular structure identification to identify novel biomarkers for metabolic disease

Human metabolism generates ten thousands of small molecules regulating important functions in our physiology. Dysruptions of metabolic enzymes by genetic mutations result in severe, debilitating diseases, called Inborn Metabolic Disorders (IMDs). IMDs are among the top 3 of most deadly diseases in children and therapies are available for only ~15%.
Modern high-resolution mass spectrometry techniques can detect thousands of metabolites in body fluids in a single run with the potential to discover a new generation of biomarkers for early diagnosis, with prognostic value and with relevance for monitoring the side effects and benefits of innovative (genetic) therapies. However, the key challenge is that the chemical structure of most of the detected metabolite features remains unidentified. This is essential to link biomarkers with functional pathways and thus disease symptoms.
We have been developing a computational metabolomics pipeline for molecular structure identification by integrating mass spectrometry and InfraRed Ion Spectroscopy (IRIS). In combination with chemical synthesis of defined standards, this has allowed us to identify novel biomarkers for early diagnosis in pyridoxin-dependent epilepsy, GLUT1 deficiency and several other IMDs.

Speaker: Dirk Lefeber (Radboud University Medical Center)

25 Gas phase IR spectroscopy in helium nanodroplets of non-classical carbocations

Carbocations, as reactive intermediates, play a significant role in many organic reactions. A detailed description of their structure and stability is relevant in the understanding of such reactions and thus crucial for modern synthetic chemistry. Carbocations are distinguished into two classes, classical (carbenium) and non-classical (carbonium) carbocations, where the non-classical carbocations are distinguished by a 2-center-3-electron bond at the central carbon atom. Historically, the debate around non-classical carbocations has been dominated by discussions about the structure of the 2-norbornyl cation. Its non-classical structure, proposed as early as 1949 by Saul Winstein, sparked a passionate debate, influencing and driving forward the advancement of several spectroscopic, experimental, and theoretical methods. In recent developments, XRD imaging of the crystal structure of the 2-norbornyl cation have shown its non-classical properties. Nevertheless, the gas phase structure remains unclear.
In this study, we investigated the non-classical structure and isomerization reactions of the norbornyl system in the gas phase, using infrared action spectroscopy in helium nanodroplets, employing coherent infrared photons from the Free-Electron Laser at the Fritz Haber Institute (FHI-FEL). The well resolved IR action spectra, obtained at the cryogenic temperature of 0.37 K, aided by quantum chemistry calculations, are extremely useful to determine the molecular structure of ionic species. For the norbornyl system, three possible isomerization products were investigated, and the product composition gave insight into energy contributions from experimental parameters via kinetic selectivity. By this, the isomerization of the norbornyl system was partially prevented, allowing the investigation of the non-classical structure of the 2-norbornyl cation in the gas phase for the first time.

Speaker: David Battke (Fritz-Haber-Institut)

26 Fragmentation mechanisms of corticosteroids, androgens and progestogens revealed by IRMPD spectroscopy

Steroidal hormones play a crucial role as chemical messengers within organisms. Their profound influence on various physiological processes makes them a prime focus for analysis in healthcare and many other biochemical fields. While their metabolic pathways are extensively studied and numerous MS(/MSn) spectra are available (e.g., in the HMDB), the fragmentation pathways of steroidal hormones and their derivatives in tandem mass spectrometry are yet to be completely understood. The complex fragmentation mechanisms of steroids pose significant challenges in interpreting MSn spectra and elucidating fragment structures. This work aims to characterize MS/MS fragments using infrared ion spectroscopy (IRIS) and propose potential candidate structures.

Speaker: Laura Finazzi (HFML-FELIX)

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