Focused ion beam-induced deposition (FIBID) relies on controlled ion-matter interactions, but the fundamental dissociation pathways of many potential precursor molecules remain largely unexplored. In this work, we investigate the ion-induced fragmentation of the FEBID/FIBID-relevant precursor Fe(CO) _4 (acrolein) in the gas phase. Using time-of-flight mass spectrometry, we measure the fragmentation patterns resulting from collisions with He ^+ (16 keV), Ne ^+ (6 keV), and Ne ^4+ (40 keV) projectiles, covering interaction regimes from predominantly electronic stopping to higher nuclear stopping contributions. The results reveal pronounced dissociation of the ligand framework and substantial loss of functional groups, consistent with efficient energy redistribution within the metal-carbonyl core. Ne ^+ is identified as a particularly efficient projectile for inducing molecular decomposition. The data provide new insight into the stability, energy-dissipation pathways, and FIBID-relevant behaviour of Fe(CO) _4 (acrolein), offering a basis for understanding its decomposition mechanisms and comparison to other iron precursors. Schematic representation of focused ion beam-induced deposition (FIBID) and mass spectrometric analysis.

We investigate two nitrogen-containing isomers of polycyclic aromatic hydrocarbons, quinoline and isoquinoline, of composition C9H7N in collisions with 7 keV O+ and 48 keV O6+ projectile ions. By employing ion–ion coincidence mass spectrometry, we determine branching ratios for H-loss, C2H2-loss, and HCN-loss dissociation channels of Q2+ and IQ2+. The overall contribution of HCN loss is found to be the dominant decay channel. A comparison with the results of a parallel experiment on naphthalene, the simplest PAH, reveals that HCN loss in both isomers has a higher propensity than the analogous C2H2 loss of naphthalene. The positional identity of the nitrogen atom in the two isomers mainly manifests in many-body fragmentation of their dications. Potential energy surfaces of Q2+ and IQ2+ are further computed to explore complete fragmentation mechanisms. Parent dications (Q2+ and IQ2+) are identified to isomerize via seven-membered ring structures before elimination of C2H2 and HCN. While prompt dissociation is the primary pathway, the dominant channel of each neutral-loss class also exhibits delayed fragmentation.

The present work is a continuation of our studies with iron pentacarbonyl, a model organometallic precursor for Focused Ion Beam-Induced Deposition (FIBID). Interactions of He2+(16 keV), Ne+(6 keV), Ne4+(40 keV), Ar2+(12 keV) and Ar8+(64 keV) projectile ions with [Fe(CO)5]n clusters are studied using TOF mass spectrometry. The clusters represent an intermediate between the gas phase and the bulk environment and can be used as a proxy for the processes in complex environments such as e.g. the nanostructure deposition. The addition of environment in the present study results in the observation of fragments with high kinetic energies ejected from clusters, an overall reduction of the fragmentation, and observation of a range of fragments associated with C-O bond dissociation, not observed for isolated molecules. On the other hand, the high efficiency of the Ne+ projectile in fragmenting the Fe(CO)5 isolated molecule is also observed in clusters.

We present a joint theoretical-experimental study on the inner-shell photoionization of hypoxanthine clusters in the gas phase. Simulations were performed using a computational strategy that combines molecular dynamics to explore the conformers of the clusters, density functional theory for geometry optimization and inner shell photoionization calculations. Two main intermolecular interactions are observed: hydrogen-bonds (HB) and pi - pi stacking. When increasing the cluster size, a combination of both kinds of interaction occurs. We show that such intermolecular interactions play a role in the chemical shift observed in X-ray photoemission spectroscopy experiments. In particular, we highlight the interplay between charge depletion and charge accumulation in regions where HBs stabilize the clusters.

We have investigated the fragmentation dynamics of the organometallic ferrocene molecule after interaction with multiply charged ions using multicoincidence mass spectrometry and quantum chemistry calculations. We observed unexpected fragmentation dynamics of the two-body breakup channels from ferrocene dications revealing a charge screening effect from the iron atom and delayed fragmentation dynamics. These observations are rationalized through the population of a specific long-lived excited state, where one positive charge is located on each cyclopentadienyl ring. Combined experiment/theory study on ionized ferrocene molecules. We found that, due to the population of a specific long-lived excited state, charge screening effects from the iron atom and delayed fragmentations occur leading to unexpected dynamics.

Bond-forming reactions induced in mixed clusters of coronene and C60 by energetic impact of argon ions are modeled using molecular dynamics simulations. A wide range of reaction products and growth mechanisms are identified.

Grazing incidence fast atom diffraction (GIFAD or FAD) has become a technique to track the surface topology of crystal surface at the atomic scale. The paper retraces the events that led to the discovery of unexpected quantum behavior of keV atoms during the thesis of Patrick Rousseau in Orsay and Andreas Schueller in Berlin. In Orsay, it started by diffraction spots whereas in Berlin supernumerary rainbows were first identified at keV. Though the discovery was not anticipated, it did not take place by accident, everything was in place several years before, waiting only for an interest in neutral projectiles with a touch of curiosity.

The GTS ion source, operated at 14.5GHz, provides multiply charged heavy ion beams for the ARIBE facility at GANIL. The facility variety is limited by the efficiency of the extraction especially in the few keV/q domain. In order to improve the ion source, the extraction system was upgraded numerically using IBSimu. The shape of the plasma and the puller electrodes was changed. It causes the increase of the electric field near the plasma meniscus and allows the use of lower extraction voltages at constant total ion beam current. The required beam parameters were taken from the experimental data. The opportunity of effective low energy beam formation (at a few keV/q or several hundreds eV/q beam energy) was studied. The high current and low energy ion beam production will provide new possibilities for ARIBE facility users.

In a recent work, we have shown that photon absorption can cause a chemical bond to be created between the two monomers within a protonated serine dimer, a process known as intra-cluster bond formation, despite this process not occurring following thermal excitation via low energy collision-induced dissociation (LE-CID). Here we show further evidence for non-statistical photon-induced dissociation (PID) of the protonated serine dimer. In addition we discuss LE-CID and PID studies of the protonated serine octamer, showing that in this case as well, PID leads to non-statistical fragmentation and to the formation of two bonds between three neighboring monomers.

Adamantane, the smallest diamondoid molecule with a symmetrical cage, contains two distinct carbon sites, CH and CH2. The ionization/excitation of the molecule leads to the cage opening and strong structural reorganization. While theoretical predictions suggest that the carbon site CH primarily causes the cage opening, the role of the other CH2 site remains unclear. In this study, we used advanced experimental Auger electron–ion coincidence techniques and theoretical calculations to investigate the fragmentation dynamics of adamantane after resonant inner-shell photoexcitation. Our results demonstrate that some fragmentation channels exhibit site-sensitivity of the initial core–hole location, indicating that different carbon site excitations could lead to unique cage opening mechanisms.

The valence ionization of uracil and mixed water-uracil clusters has been studied experimentally and by ab initio calculations. In both measurements, the spectrum onset shows a red shift with respect to the uracil molecule, with the mixed cluster characterized by peculiar features unexplained by the sum of independent contributions of the water or uracil aggregation. To interpret and assign all the contributions, we performed a series of multi-level calculations, starting from an exploration of several cluster structures using automated conformer-search algorithms based on a tight-binding approach. Ionization energies have been assessed on smaller clusters via a comparison between accurate wavefunction-based approaches and cost-effective DFT-based simulations, the latter of which were applied to clusters up to 12 uracil and 36 water molecules. The results confirm that (i) the bottom-up approach based on a multilevel method [Mattioli et al. Phys. Chem. Chem. Phys. 23, 1859 (2021)] to the structure of neutral clusters of unknown experimental composition converges to precise structure-property relationships and (ii) the coexistence of pure and mixed clusters in the water-uracil samples. A natural bond orbital (NBO) analysis performed on a subset of clusters highlighted the special role of H-bonds in the formation of the aggregates. The NBO analysis yields second-order perturbative energy between the H-bond donor and acceptor orbitals correlated with the calculated ionization energies. This sheds light on the role of the oxygen lone-pairs of the uracil CO group in the formation of strong H-bonds, with a stronger directionality in mixed clusters, giving a quantitative explanation for the formation of core-shell structures.

Angewandte ChemieVolume 135, Issue 15 e202381511 Graphisches InhaltsverzeichnisFree Access Graphisches Inhaltsverzeichnis: Angew. Chem. 15/2023 First published: 26 March 2023 https://doi.org/10.1002/ange.202381511AboutPDF ToolsRequest permissionAdd to favorites ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Volume135, Issue15April 3, 2023e202381511 This is the German version of Angewandte Chemie. Note for articles published since 1962: Do not cite this version alone. Take me to the International Edition version with citable page numbers, DOI, and citation export. We apologize for the inconvenience. RelatedInformation

Possible routes for intra-cluster bond formation (ICBF) in protonated serine dimers have been studied. We found no evidence of ICBF following low energy collision-induced dissociation (in correspondence with previous works), however, we do observe clear evidence for ICBF following photon absorption in the 4.6-14 eV range. Moreover, the comparison of photon-induced dissociation measurements of the protonated serine dimer to those of a protonated serine dipeptide provides evidence that ICBF, in this case, involves peptide bond formation (PBF). The experimental results are supported by ab initio molecular dynamics and exploration of several excited state potential energy surfaces, unraveling a pathway for PBF following photon absorption. The combination of experiments and theory provides insight into the PBF mechanisms in clusters of amino acids, and reveals the importance of electronic excited states reached upon UV/VUV light excitation.

We investigate the fragmentation dynamics of adamantane dications produced after core-ionization at the carbon edge followed by Auger decay. The combination of high-resolution electron spectroscopy, energy-resolved electron-ion multi-coincidence spectroscopy and different theoretical models allows us to give a complete characterization of the processes involved after ionization. We show that energy- and site-sensitivity is observed even for a highly-symmetric molecule that lacks any unique atomic site.

The design and performances of a newly built electrostatic charge state analyzer constructed to act as a spectrometer for keV/u ions are reported. It consists of two 90∘ curved electrodes enclosed by Matsuda electrodes. This setup was recently tested using Ar9+ and Ar12+ ion beams at an energy of 10 keV per charge unit. This spectrometer achieves a good separation of different charge states formed by electron capture processes during collisions between primary ions and the residual gas. Thanks to these first tests, we have identified up to three different background contributions on the detector that need to be reduced or suppressed.

We present a combined experimental and theoretical study of the fragmentation of singly and doubly N-methylated glycine (sarcosine and N,N-dimethyl glycine, respectively) induced by low-energy (keV) O6+ ions. Multicoincidence mass spectrometry techniques and quantum chemistry simulations (ab initio molecular dynamics and density functional theory) allow us to characterise different fragmentation pathways as well as the associated mechanisms. We focus on the fragmentation of doubly ionised species, for which coincidence measurements provide unambiguous information on the origin of the various charged fragments. We have found that single N-methylation leads to a larger variety of fragmentation channels than in no methylation of glycine, while double N-methylation effectively closes many of these fragmentation channels, including some of those appearing in pristine glycine. Importantly, the closure of fragmentation channels in the latter case does not imply a protective effect by the methyl group.

The properties of mixed water-uracil nanoaggregates have been probed by core electron-photoemission measurements to investigate supramolecular assembly in the gas phase driven by weak interactions. The interpretation of the measurements has been assisted by multilevel atomistic simulations, based on semi-empirical tight-binding and DFT-based methods. Our protocol established a positive-feedback loop between experimental and computational techniques, which has enabled a sound and detailed atomistic description of such complex heterogeneous molecular aggregates. Among biomolecules, uracil offers interesting and generalized skeletal features; its structure encompasses an alternation of hydrophilic H-bond donor and acceptor sites and hydrophobic moieties, typical in biomolecular systems, that induces a supramolecular core-shell-like organization of the mixed clusters with a water core and an uracil shell. This structure is far from typical models of both solid-state hydration, with water molecules in defined positions, or liquid solvation, where disconnected uracil molecules are completely surrounded by water.

A detailed description of a custom-made gas aggregation cluster source is given as well as of its coupling to permanent molecular beam end-stations of the beamlines DESIRS and PLEIADES at the French national facility synchrotron SOLEIL. Using (hydrated) hypoxanthine clusters as a case study, the production of clusters with different source parameters is discussed based on Vacuum Ultra-Violet (VUV) mass spectrometry. The ability of the cluster source to perform photoelectron spectroscopy is illustrated by photoelectron spectra obtained for valence and core shells.

Emerging experimental techniques combined with theoretical advances allow unprecedented studies of the dynamics of gas phase molecules and clusters induced in interactions with photons, electrons, or heavy particles. Here, the authors highlight recent advances, key open questions, and challenges in this field of research with focus on experimental studies of dynamics of ions stored on millisecond timescales and beyond, and its applications in astrochemistry and astronomy.

The way molecules break after ion bombardment is intimately related to the early electron dynamics generated in the system, in particular, charge (or electron) migration. We exploit the natural positive-negative charge splitting in the zwitterionic molecule betaine to selectively induce double electron removal from its negatively charged side by impact of fast O6+ ions. The loss of two electrons in this localized region of the molecular skeleton triggers a competition between direct Coulomb explosion and charge migration that is examined to obtain temporal information from ion-ion coincident measurements and nonadiabatic molecular dynamics calculations. We find a charge migration time, from one end of the molecule to the other, of approximately 20 to 40 femtoseconds. This migration time is longer than that observed in molecules irradiated by ultrashort light pulses and is the consequence of charge migration being driven by adiabatic nuclear dynamics in the ground state of the molecular dication.