X-ray absorption spectroscopy of FeH to aid its identification in astrochemical environments.

We present the first absorption spectrum of the unperturbed diatomic molecular ion FeH in any wavelength range. The cryogenic X-ray absorption spectrum at the L and L edge is consistent with an iron 3d occupation of 6.24e.

Symmetry reduction induced by argon tagging gives access to low-lying excited states of FeH in the overtone region of the Fe-H stretching mode.

Iron is the most abundant transition metal in the interstellar medium (ISM), and is thought to be involved in a variety of astrochemical processes. Here, we present the infrared multiple photon dissociation (IRMPD) spectra of ArFeH and their deuterated isotopologues in the region of 2240-14 000 cm. The Fe-H overtone stretching mode in ArFeH and ArFeH is observed at 3636 ± 28 cm and 3659 ± 13 cm, respectively.

Multiconfigurational Character of Repulsive AΣ State Leaves Strong Signature in the Photodissociation Spectrum of Zn.

For the excitation to a repulsive state of a diatomic molecule, one expects a single broad peak in the photodissociation spectrum. For Zn, however, two peaks for the spin- and symmetry-allowed AΣ ← XΣ transition are observed. A detailed quantum-chemical analysis reveals pronounced multiconfigurational character of the AΣ state.

Master equation modeling of blackbody infrared radiative dissociation (BIRD) of hydrated peroxycarbonate radical anions.

Molecular cluster ions, which are stored in an electromagnetic trap under ultra-high vacuum conditions, undergo blackbody infrared radiative dissociation (BIRD). This process can be simulated with master equation modeling (MEM), predicting temperature-dependent dissociation rate constants, which are very sensitive to the dissociation energy. We have recently introduced a multiple-well approach for master equation modeling, where several low-lying isomers are taken into account.

Magic cluster sizes of cationic and anionic sodium chloride clusters explained by statistical modeling of the complete phase space.

As one of the main components of sea salt aerosols, sodium chloride is involved in numerous atmospheric processes. Gas-phase clusters are ideal models to study fundamental physical and chemical properties of sodium chloride, which are significantly affected by the cluster size. Of particular interest are magic cluster sizes, which exhibit high intensities in mass spectra.

Iron Complexes as Potential Carriers of Diffuse Interstellar Bands: The Photodissociation Spectrum of Fe(HO) at Optical Wavelengths.

The fullerene ion C is the only carrier of diffuse interstellar bands (DIBs) identified so far. Transition-metal compounds feature electronic transitions in the visible and near-infrared regions, making them potential DIB carriers. Since iron is the most abundant transition metal in the cosmos, we here test this idea with Fe(HO).

Spectroscopy of cluster aerosol models: IR and UV spectra of hydrated glyoxylate with and without sea salt.

Glyoxylic acid is formed in the troposphere by oxidation of organic molecules. In sea salt aerosols, it is expected to be present as glyoxylate, integrated into the salt environment and strongly interacting with water molecules. In water, glyoxylate is in equilibrium with its -diol form.

Carbon Dioxide and Water Activation by Niobium Trioxide Anions in the Gas Phase.

Transition metals are important in various industrial applications including catalysis. Due to the current concentration of CO in the atmosphere, various ways for its capture and utilization are investigated. Here, we study the activation of CO and HO at [NbO] in the gas phase using a combination of infrared multiple photon dissociation spectroscopy and density functional theory calculations.

Surface or Internal Hydration - Does It Really Matter?

The precise location of an ion or electron, whether it is internally solvated or residing on the surface of a water cluster, remains an intriguing question. Subtle differences in the hydrogen bonding network may lead to a preference for one or the other. Here we discuss spectroscopic probes of the structure of gas-phase hydrated ions in combination with quantum chemistry, as well as H/D exchange as a means of structure elucidation.

Thermally Activated vs. Photochemical Hydrogen Evolution Reactions-A Tale of Three Metals.

Molecular processes behind hydrogen evolution reactions can be quite complex. In macroscopic electrochemical cells, it is extremely difficult to elucidate and understand their mechanism. Gas phase models, consisting of a metal ion and a small number of water molecules, provide unique opportunities to understand the reaction pathways in great detail.

Simplified Multiple-Well Approach for the Master Equation Modeling of Blackbody Infrared Radiative Dissociation of Hydrated Carbonate Radical Anions.

Blackbody infrared radiative dissociation (BIRD) in a collision-free environment is a powerful method for the experimental determination of bond dissociation energies. In this work, we investigate temperature-dependent BIRD of CO(HO) at 250-330 K to determine water binding energies and assess the influence of multiple isomers on the dissociation kinetics. The ions are trapped in a Fourier-transform ion cyclotron resonance mass spectrometer, mass selected, and their BIRD kinetics are recorded at varying temperatures.

Toward Detection of FeH in the Interstellar Medium: Infrared Multiple Photon Dissociation Spectroscopy of ArFeH.

The iron hydride molecular cation FeH is expected to be present in the interstellar medium. Because of the lack of laboratory data, it is yet to be identified in spectrally resolved astronomic observations. As a benchmark for computational predictions and to guide an experimental search for the ro-vibrational lines of FeH, we performed infrared multiple photon dissociation (IRMPD) spectroscopy of FeH tagged with two argon atoms.

Size-dependent H and H formation by infrared multiple photon dissociation spectroscopy of hydrated vanadium cations, V(HO), = 3-51.

Infrared spectra of the hydrated vanadium cation (V(HO); = 3-51) were measured in the O-H stretching region employing infrared multiple photon dissociation (IRMPD) spectroscopy. Spectral fingerprints, along with size-dependent fragmentation channels, were observed and rationalized by comparing to spectra simulated using density functional theory. Photodissociation leading to water loss was found for cluster sizes = 3-7, consistent with isomers featuring intact water ligands.

Infrared Multiple Photon Dissociation Spectroscopy Confirms Reversible Water Activation in Mn(HO), ≤ 8.

Controlled activation of water molecules is the key to efficient water splitting. Hydrated singly charged manganese ions Mn(HO) exhibit a size-dependent insertion reaction, which is probed by infrared multiple photon dissociation spectroscopy (IRMPD) and FT-ICR mass spectrometry. The noninserted isomer of Mn(HO) is formed directly in the laser vaporization ion source, while its inserted counterpart HMnOH(HO) is selectively prepared by gentle removal of water molecules from larger clusters.

Photochemical Hydrogen Evolution at Metal Centers Probed with Hydrated Aluminium Cations, Al (H O) , n=1-10.

Hydrated aluminium cations have been investigated as a photochemical model system with up to ten water molecules by UV action spectroscopy in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. Intense photodissociation was observed starting at 4.5 eV for two to eight water molecules with loss of atomic hydrogen, molecular hydrogen and water molecules.

Photochemistry and UV/vis spectroscopy of hydrated vanadium cations, V(HO), = 1-41, a model system for photochemical hydrogen evolution.

Photochemical hydrogen evolution provides fascinating perspectives for light harvesting. Hydrated metal ions in the gas phase are ideal model systems to study elementary steps of this reaction on a molecular level. Here we investigate mass-selected hydrated monovalent vanadium ions, with a hydration shell ranging from 1 to 41 water molecules, by photodissociation spectroscopy.

Asymmetric Solvation of the Zinc Dimer Cation Revealed by Infrared Multiple Photon Dissociation Spectroscopy of Zn(HO) ( = 1-20).

Investigating metal-ion solvation-in particular, the fundamental binding interactions-enhances the understanding of many processes, including hydrogen production via catalysis at metal centers and metal corrosion. Infrared spectra of the hydrated zinc dimer (Zn(HO); = 1-20) were measured in the O-H stretching region, using infrared multiple photon dissociation (IRMPD) spectroscopy. These spectra were then compared with those calculated by using density functional theory.

Getting Ready for the Hydrogen Evolution Reaction: The Infrared Spectrum of Hydrated Aluminum Hydride-Hydroxide HAlOH (H O) , n=9-14.

Hydrated singly charged aluminum ions eliminate molecular hydrogen in a size regime from 11 to 24 water molecules. Here we probe the structure of HAlOH (H O) , n=9-14, by infrared multiple photon spectroscopy in the region of 1400-2250 cm . Based on quantum chemical calculations, we assign the features at 1940 cm and 1850 cm to the Al-H stretch in five- and six-coordinate aluminum(III) complexes, respectively.

Spectroscopy and photochemistry of copper nitrate clusters.

The investigation of copper nitrate cluster anions Cu(ii)n(NO3)2n+1-, n ≤ 4, in the gas phase using ultraviolet/visible/near-infrared (UV/vis/NIR) spectroscopy provides detailed insight into the electronic structure of the copper salt and its intriguing photochemistry. In the experimentally studied region up to 5.5 eV, the spectra of copper(ii) nitrate exhibit a 3d-3d band in the vis/NIR and well-separated bands in the UV.

Infrared spectroscopy of CO (HO) and CO (HO).

Hydrated molecular anions are present in the atmosphere. Revealing the structure of the microsolvation is key to understanding their chemical properties. The infrared spectra of CO (HO) and CO (HO) were measured via infrared multiple photon dissociation spectroscopy in both warm and cold environments.

Microsolvation of Zn cations: infrared multiple photon dissociation spectroscopy of Zn(HO) (n = 2-35).

The structures, along with solvation evolution, of size-selected Zn(HO) (n = 2-35) complexes have been determined by combining infrared multiple photon photodissociation (IRMPD) spectroscopy and density functional theory. The infrared spectra were recorded in the O-H stretching region, revealing varying shifts in band position due to different water binding motifs. Concordant with previous studies, a coordination number of 3 is observed, determined by the sudden appearance of a broad, red-shifted band in the hydrogen bonding region for clusters n > 3.

Infrared multiple photon dissociation spectroscopy of anionic copper formate clusters.

We investigate the structure of copper formate and deuterated copper formate clusters using infrared multiple photon dissociation in combination with quantum chemical calculations. Symmetric and asymmetric C-O stretching vibrations along with C-H/C-D stretching vibrations were characterized. Fermi interactions between the C-H stretch and likely a C-O combination band and/or the overtone of a C-H in-plane bending motion have been confirmed by deuteration.

IR multiple photon dissociation spectroscopy of MO (M = V, Nb, Ta).

A laser vaporization cluster source is coupled to the Fourier-transform ion cyclotron resonance mass spectrometer beamline of the free-electron laser for intracavity experiments. Gas phase metal ions and their oxides (VO , NbO , and TaO ) are formed and spectroscopically characterized using IR multiple-photon dissociation spectroscopy via loss of atomic oxygen and overcoming fragmentation energies of 3 eV-6 eV. The signal is observed for all MO fundamental modes: the symmetric and anti-symmetric ν and ν stretch modes in the 900 cm-1000 cm range and the ν bending mode in the 300 cm-450 cm range.

Photochemical activation of carbon dioxide in Mg(CO)(HO).

We combine multi-reference ab initio calculations with UV-VIS action spectroscopy to study photochemical activation of CO on a singly charged magnesium ion, [MgCO(HO)], as a model system for the metal/ligand interactions relevant in CO photochemistry. For the non-hydrated species, two separated Mg 3-3 bands are observed within 5.0 eV.