A5103018914- Quantum, superfluid, helium dynamics
- Advanced Chemical Physics Studies
- Crystallization and Solubility Studies
- Molecular Spectroscopy and Structure
- Cold Atom Physics and Bose-Einstein Condensates
- Atomic and Subatomic Physics Research
- X-ray Diffraction in Crystallography
- Astrophysics and Star Formation Studies
- Fullerene Chemistry and Applications
- Hydrogen Storage and Materials
- Electron Spin Resonance Studies
- Spectroscopy and Quantum Chemical Studies
- Atomic and Molecular Physics
- Tree-ring climate responses
- Physics of Superconductivity and Magnetism
- Solid-state spectroscopy and crystallography
- Spacecraft and Cryogenic Technologies
- Photosynthetic Processes and Mechanisms
- Advanced NMR Techniques and Applications
- Methane Hydrates and Related Phenomena
- Arctic and Antarctic ice dynamics
- Climate change and permafrost
- Surface Chemistry and Catalysis
- Photoreceptor and optogenetics research
- High-pressure geophysics and materials
Universität Innsbruck
1978-2022
Osnabrück University
2004-2005
Freie Universität Berlin
2004
Institut de Biologie Structurale
2004
Centre National de la Recherche Scientifique
2004
Laboratoire d'Ingénierie des Systèmes Macromoléculaires
2004
Abstract Helium has a unique phase diagram and below 25 bar it does not form solid even at the lowest temperatures. Electrostriction leads to formation of layer helium around charged impurities much lower pressures in liquid superfluid helium. These so-called ‘Atkins snowballs’ have been investigated for several simple ions. Here we He n C 60 + complexes with exceeding 100 via electron ionization nanodroplets doped . Photofragmentation these is measured by merging tunable narrow-bandwidth...
In 2015, Campbell et al. (Nature 523, 322) presented spectroscopic laboratory gas phase data for the fullerene cation, C$_{60}^+$, that coincide with reported astronomical spectra of two diffuse interstellar band (DIB) features at 9633 and 9578 \AA. following year additional were linked to three other weaker DIBs 9428, 9366, 9349 The obtained using wavelength-dependent photodissociation spectroscopy small (up three) He-tagged C$_{60}^+-$He$_n$ ion complexes, yielding rest wavelengths bare...
In the last decade, joint efforts of biologists, chemists and physicists have helped in understanding dominant factors determining specificity directionality transmembrane transfer processes proteins. this endeavor, electron paramagnetic resonance (EPR) spectroscopy has played an important role. Characteristic examples such are hydrogen-bonding patterns polarity effects microenvironment protein sites involved process. These may undergo characteristic changes during reaction and, thereby,...
We report the first experimental observation of negatively charged hydrogen and deuterium cluster ions, H_{n}^{-} D_{n}^{-}, where n≥5. These anions are formed by an electron addition to liquid helium nanodroplets doped with molecular or deuterium. The ions stable for at least lifetime experiment, which is several tens microseconds. Only odd values n detected, some specific show anomalously high abundances. sizes these "magic number" suggest icosahedral framework H_{2} (D_{2}) molecules in...
Helium is considered an almost ideal tagging atom for cold messenger spectroscopy experiments. Although helium bound very weakly to the ionic molecule of interest, tags can lead shifts and broadenings that we recorded near 963.5 nm in electronic excitation spectrum C60+ solvated with up 100 atoms. Dedicated quantum calculations indicate inhomogeneous broadening due different binding energies pentagonal hexagonal faces C60+, their dependence on state, numerous isomeric structures become...
We report the first experimental study of attachment multiple foreign atoms to a cationic polycyclic aromatic hydrocarbon (PAH). The chosen PAH was coronene, C24H12, which added liquid helium nanodroplets and then subjected electron bombardment. Using mass spectrometry, coronene cations decorated with were clearly seen spectrum shows peaks anomalously high intensities (“magic number” peaks), represent ion-helium complexes stability. data suggest formation rigid layer consisting 38 that...
The pore-forming bacterial toxins of the colicin family undergo massive protein refolding, while attacking a target cell, to convert from water-soluble conformational state membrane-associated with subsequent insertion helical hairpins into cytoplasmic membrane. To explore validity proposed models for mechanism by which soluble channel-forming domain A turns inside out upon membrane association, five site-specific cysteine mutants A, each singly spin labeled nitroxide side chains, were...
We report the observation of sequential encounters fullerenes with C atoms in an extremely cold environment. Experiments were performed helium droplets at 0.37 K doped C60 molecules and derived from a novel, pure source atoms. Very high-resolution mass spectra revealed formation carbenes type C60(C:)n n up to 6. Bridge-type bonding adatoms form known dumbbell C60═C═C60 also was observed. Density functional theory calculations that elucidated carbene character species their structures. Mass...
The reactions of carbon atoms with dihydrogen have been investigated in liquid helium droplets at $T$ = 0.37 K. A calorimetric technique was applied to monitor the energy released reaction. barrierless reaction between a single atom and molecule detected. Reactions clusters studied by high-resolution mass spectrometry. formation hydrocarbon cations type C$_m$H$_n^+$, $m$ 1-4 $n$ 1-15 observed. With enhanced concentration dihydrogen, spectra demonstrated main "magic" peak assigned CH$_5^+$...
The parallel-displaced coronene dimer; the number of strongly adsorbed H<sub>2</sub> (red spheres) measures extent displacement.
Interactions of atomic cations with molecular hydrogen are interest for a wide range applications in technologies. These interactions fairly strong despite being non-covalent, hence one can ask whether molecules would form dense, solid-like, solvation shells around the ion (snowballs) or rather more weakly bound compound. In this work, between Cs+ and H2 studied both experimentally computationally. Isotopic substitution by D2 is also investigated. On hand, helium nanodroplets doped cesium...
Electron ionization of helium droplets doped with sodium, potassium or cesium results in doubly and triply charged cluster ions that are much smaller than previously observed.
We report the first observation of cations, dications and trications large clusters adamantane. Cluster formation was initiated near 0 K in helium droplets ionization achieved with one or more collisions energetic He species (He$^{\star}$, He$^{+}$ He$^{\star}$$^{-}$). The occurrence Coulomb explosion appeared to discriminate against small multiply charged clusters. High resolution mass spectrometry revealed presence "magic number" m/z peaks that can be attributed packing adamantane...
Helium nanodroplets are doped with cesium and molecular hydrogen subsequently ionized by electrons. Mass spectra reveal HxCs+ ions that contain as many 130 atoms. Two features in the striking: First, abundance of an odd number atoms is very low; HCs+ only 1% H2Cs+. The dominance even-numbered species stark contrast to previous studies pure or cluster ions. Second, (H2)nCs+ anomalies at n = 8, 12, 32, 44, 52. Guided work on solvated helium, we assign 44 formation three concentric, solid-like...
Adducts between gold cluster ions and helium atoms reveal the underlying ion structure.
Ionic complexes between gold and C60 have been observed for the first time. Cations anions of type [Au(C60)2]+/– are shown to particular stability. Calculations suggest that these ions adopt a C60–Au–C60 sandwich-like (dumbbell) structure, which is reminiscent [XAuX]+/– previously much smaller ligands. The can be regarded as Au(I) complexes, regardless whether net charge positive or negative, but in both cases, transfer Au incomplete, most likely because covalent contribution Au–C60 binding....
Double magic: 12 adamantane “nanodiamonds” surround, in an icosahedric arrangement, 21 water molecules that form a pentagon dodecahedral structure.
We investigate the photodissociation of helium-solvated cesium dimer cations using action spectroscopy and quantum chemical calculations. The spectrum Cs2He+ shows three distinct absorption bands into both bound dissociative states. Upon solvation with further helium atoms, considerable shifts are observed, exceeding 0.1 eV (850 cm-1) already for Cs2He10+, along significant broadening. highly sensitive to character excited state. Our calculations show that atoms adsorb on ends Cs2+....
We have studied complexes of gold atoms and imidazole (C$_3$N$_2$H$_4$, abbreviated Im) produced in helium nanodroplets. Following the ionization doped droplets we detect a broad range different Au$_m$Im$_n^+$ complexes, however find that for specific values $m$ certain $n$ are "magic" thus particularly abundant. Our density functional theory calculations indicate these abundant clusters sizes partially result stable e.g. AuIm$_2^+$, due to transition fragmentation patterns from loss neutral...
The adsorption of helium on charged hexabenzocoronene (Hbc, C42H18), a planar polycyclic aromatic hydrocarbon (PAH) molecule D6h symmetry, was investigated by combination high-resolution mass spectrometry and classical quantum computational methods. ion abundance HenHbc+ complexes versus size n features prominent local anomalies at = 14, 38, 68, 82, weak one 26, indicating that for these “magic” sizes, the evaporation energies are relatively large. Surprisingly, spectra anionic HenHbc−...