gas phase vibrational spectroscopy of V3O6-8+

We present gas phase vibrational spectra of the trinuclear vanadium oxide cations V3O6+·He1–4, V3O7+·Ar0,1, and V3O8+·Ar0,2 between 350 and 1200 cm−1. Cluster structures are assigned based on a comparison of the experimental and simulated IR spectra. The latter are derived from B3LYP/TZVP calculations on energetically low-lying isomers identified in a rigorous search of the respective configurational space, using higher level calculations when necessary. V3O7+ has a cage-like structure of C3v symmetry. Removal or addition of an O-atom results in a substantial increase in the number of energetically low-lying structural isomers. V3O8+ also exhibits the cage motif, but with an O2 unit replacing one of the vanadyl oxygen atoms. A chain isomer is found to be most stable for V3O6+. The binding of the rare gas atoms to V3O6–8+ clusters is found to be strong, up to 55 kJ/mol for Ar, and markedly isomer-dependent, resulting in two interesting effects. First, for V3O7+·Ar and V3O8+·Ar an energetic reordering of the isomers compared to the bare ion is observed, making the ring motif the most stable one. Second, different isomers bind different number of rare gas atoms. We demonstrate how both effects can be exploited to isolate and assign the contributions from multiple isomers to the vibrational spectrum. The present results exemplify the structural variability of vanadium oxide clusters, in particular, the sensitivity of their structure on small perturbations in their environment

The Integrated Carbon Observation System in Europe

Since 1750, land-use change and fossil fuel combustion has led to a 46% increase in the atmospheric carbon dioxide (CO2) concentrations, causing global warming with substantial societal consequences. The Paris Agreement aims to limit global temperature increases to well below 2 degrees C above preindustrial levels. Increasing levels of CO2 and other greenhouse gases (GH6s), such as methane (CH4) and nitrous oxide (N2O), in the atmosphere are the primary cause of climate change. Approximately half of the carbon emissions to the atmosphere are sequestered by ocean and land sinks, leading to ocean acidification but also slowing the rate of global warming. However, there are significant uncertainties in the future global warming scenarios due to uncertainties in the size, nature, and stability of these sinks. Quantifying and monitoring the size and timing of natural sinks and the impact of climate change on ecosystems are important information to guide policy-makers' decisions and strategies on reductions in emissions. Continuous, long-term observations are required to quantify GHG emissions, sinks, and their impacts on Earth systems. The Integrated Carbon Observation System (ICOS) was designed as the European in situ observation and information system to support science and society in their efforts to mitigate climate change. It provides standardized and open data currently from over 140 measurement stations across 12 European countries. The stations observe GHG concentrations in the atmosphere and carbon and GHG fluxes between the atmosphere, land surface, and the oceans. This article describes how ICOS fulfills its mission to harmonize these observations, ensure the related long-term financial commitments, provide easy access to well-documented and reproducible high-quality data and related protocols and tools for scientific studies, and deliver information and GHG-related products to stakeholders in society and policy.Peer reviewe

The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data

The FLUXNET2015 dataset provides ecosystem-scale data on CO2, water, and energy exchange between the biosphere and the atmosphere, and other meteorological and biological measurements, from 212 sites around the globe (over 1500 site-years, up to and including year 2014). These sites, independently managed and operated, voluntarily contributed their data to create global datasets. Data were quality controlled and processed using uniform methods, to improve consistency and intercomparability across sites. The dataset is already being used in a number of applications, including ecophysiology studies, remote sensing studies, and development of ecosystem and Earth system models. FLUXNET2015 includes derived-data products, such as gap-filled time series, ecosystem respiration and photosynthetic uptake estimates, estimation of uncertainties, and metadata about the measurements, presented for the first time in this paper. In addition, 206 of these sites are for the first time distributed under a Creative Commons (CC-BY 4.0) license. This paper details this enhanced dataset and the processing methods, now made available as open-source codes, making the dataset more accessible, transparent, and reproducible.Peer reviewe

Spectroscopic Investigation of Structure and Reactivity of Vanadium Oxide Clusters

#### Titel und Inhaltsverzeichnis 1. Einleitung 1 2. Methoden 5 3. Experimenteller Aufbau 23 4. Monovanadiumoxid-Kationen 45 5. Divanadiumoxid-Kationen 61 6. Trivanadiumoxid-Kationen 75 7. Vanadiumoxid-Anionen 91 8. Zusammenfassung und Ausblick 119 Literaturverzeichnis 123 A Dampfdruckkurve des Schwefeldioxides 131 B Transmissionskurven von Kbr und ZnSe 133 Veröffentlichungen 139 Kurzfassung 141 Danksagung 145Diese Arbeit wurde innerhalb des Sonderforschungsbereiches 546: Struktur, Stabilität und Reaktivität von Übergangsmetalloxid Aggregaten. durchgeführt und finanziert. Ihr Schwerpunkt liegt bei der systematischen Analyse von Vanadiumoxid-Clusterionen, bei denen es sich um wichtige Katalysatoren handelt. Zur Strukturuntersuchung wurde Infrarotspektroskopie verwendet. Die großen experimentellen Herausforderungen, die sich aus den geringen Teilchendichten und hohen Anforderungen an das Infrarotlasersystem ergeben, wurden durch Kopplung eines Tandemmassenspektrometers mit einem Freien Elektronen Laser gelöst. Durch die Verwendung indirekter Verfahren, wie der Botenatommethode, der IRMPD Spektroskopie sowie Ionenakkumulierung in einer Radiofrequenz Ionenfalle konnten trotz der geringen Teilchendichten genaue Infrarotspektren gemessen werden. Insgesamt stellt dies einen neuartigen experimentellen Ansatz zur Messung von Infrarotspektren von Gasphasenclustern dar. Für Mono- und Divanadiumoxide wurde so die Struktur und der elektronische Grundzustand eindeutig bestimmt. Hierdurch wurden zu Beginn der Arbeiten bestehende Widersprüche zwischen experimentellen und theoretischen Arbeiten behoben und vorhandene Lücken geschlossen. Die mit der Botenatommethode gemessenen Infrarot-Spektren wurden zusätzlich als Bewertungsmaß für mit Dichtefunktionaltheorie berechnete Schwingungsfrequenzen verwendet. Die systematische Analyse des Einflusses von Helium und Argon als Botenatom zeigte, dass Argon viel stärker als Helium an das Ion gebunden wird und das Infrarotspektrum des zu untersuchenden Ions beeinflusst. Beim V3O7+ führte die Adsorption von Argon z.B. zur Stabilisierung eines energetisch ungünstigen Isomers. Als wichtiges Ergebnis wird daher festgestellt, dass im Gegensatz zu Helium bei Vanadiumoxiden der Einfluss von Argon auf das zu spektroskopierende Ion nicht vernachlässigt werden kann. Eine individuelle Betrachtung jedes einzelnen Komplexes ist hier zwingend erforderlich. Bei Vanadiumoxid-Anionen kam IRMPD Spektroskopie zur Anwendung. Mit ihrer Hilfe wurde die Struktur der (V2O5-)n (n =2,3,4) Cluster bestimmt. Bei diesen drei Ionen wurde einen käfigförmiger Aufbau als gemeinsames Strukturmerkmal bestimmt. Weiterhin wurde bei diesen Ionen eine größeninduzierte d Elektron Lokalisierung nachgewiesen. Zusätzlich wurden die strukturellen Gemeinsamkeiten und Unterschiede zwischen Festkörper und diesen Clustern aufgezeigt. Vanadiumpentoxid spielt die Hauptrolle bei katalytischen Reaktionen in welche Schwefeldioxid involviert ist. Deshalb wurde die Reaktion von Schwefeldioxid mit (V2O5-)n (n =2,3,4) ebenfalls systematisch untersucht. Hierzu wurden infrarotspektroskopische Methoden mit reaktionskinetischen Experimenten verknüpft. Im Ergebnis dieser Experimente wurde der zur Bildung von Vanadiumoxid SO2 Komplexen führende Reaktionsmechanismus aufgeklärt. Die gemessenen Infrarotspektren an den entstandenen Komplexen gaben Hinweise auf eine schwache Bindung zwischen SO2 und den Vanadiumoxidanionen. Weiterhin scheint die geometrische Struktur der Vanadiumoxid Anionen durch die Schwefeldioxidadsorption nicht beeinflusst zu werden. Beim V4O10- ergaben sich Hinweise dafür, dass die Adsorption von Schwefeldioxid zu einer teilweisen Lokalisierung des im reinen Cluster delokalisierten Elektrons führt.This thesis has been funded by the Collaborative Research Center 546: Structure, stability and reactivity of transition metal oxide aggregates. . Main topic is the systematic investigation of structure and reactivity of gas phase vanadium oxide clusters. For structure investigation infrared spectroscopic methods have been used. Here experimental challenges, caused by small ion densities and high requirements on the infrared laser system were solved by coupling a tandem mass spectrometer with a Free Electron Laser. Using indirect methods, like the messenger atom method, IRMPD spectroscopy as well as ion accumulation within a radio frequency ion trap, accurate infrared spectra have been measured, despite the low ion densities. Altogether this setup represents a novel experimental approach to measure infrared spectra of gas phase cluster ions. For mono and divanadium oxide clusters a precise determination of structure and electronic ground state has been made. Thus, discrepancies between experimental and theoretical investigations, present at the beginning of this thesis, have been eliminated. Because of the high accuracy of the infrared spectra obtained by the messenger atom method, the experimental spectra were used to evaluate vibrational frequencies calculated by density functional theory. A systematic analysis of the influence of helium and argon as messenger atom has shown, argon interacts much stronger then helium with vanadium oxide cations. Thus adsorption of Argon affects structure and infrared spectroscopy of the ion, like a stabilization of an energetically unfavorable V3O7+ isomer for instance. Consequently, the influence of Argon to the ion under discover is not negligible and a special treatment of each system is necessary. For vanadium oxide anions IRMD spectroscopy has been used. Herewith the structure of (V2O5-)n (n =2,3,4) cluster anions have been identified. By this experiments polyhedral cage structures of cluster ions have been found for the first time by IRMPD spectroscopy. Evidence for size dependent charge localization has been found as well. Furthermore common and discriminating structural features of these gas phase clusters and solid vanadium oxide surfaces have been identified. Vanadium pentoxide is leading part at catalytic reactions where sulfur dioxide is involved. Consequently, reactions between sulfur dioxide and (V2O5-)n (n =2,3,4) have been investigated systematically as well. Here infrared spectroscopic methods have been combined with reaction kinetic experiments. Finally, the formation reaction mechanisms of vanadium-oxide-SO2 complexes have been found. The measured infrared spectra at the complexes formed, have given hints for a weak binding between SO2 and these vanadium oxide clusters. Consequently, the geometric structure of these anions seems not to change by adsorption of sulfur dioxide. However, at V4O10- an adsorption of sulfur dioxide seems to cause a partial localization of the electron which is total delocalized at the bare ion

Infrared spectroscopy of hydrated sulfate dianions

Contains fulltext : 98838.pdf (publisher's version ) (Open Access

The Integrated Carbon Observation System in Europe

Since 1750, land use change and fossil fuel combustion has led to a 46 % increase in the atmospheric carbon dioxide (CO2) concentrations, causing global warming with substantial societal consequences. The Paris Agreement aims to limiting global temperature increases to well below 2°C above pre-industrial levels. Increasing levels of CO2 and other greenhouse gases (GHGs), such as methane (CH4) and nitrous oxide (N2O), in the atmosphere are the primary cause of climate change. Approximately half of the carbon emissions to the atmosphere is sequestered by ocean and land sinks, leading to ocean acidification but also slowing the rate of global warming. However, there are significant uncertainties in the future global warming scenarios due to uncertainties in the size, nature and stability of these sinks. Quantifying and monitoring the size and timing of natural sinks and the impact of climate change on ecosystems are important information to guide policy-makers’ decisions and strategies on reductions in emissions. Continuous, long-term observations are required to quantify GHG emissions, sinks, and their impacts on Earth systems. The Integrated Carbon Observation System (ICOS) was designed as the European in situ observation and information system to support science and society in their efforts to mitigate climate change. It provides standardized and open data currently from over 140 measurement stations across 12 European countries. The stations observe GHG concentrations in the atmosphere and carbon and GHG fluxes between the atmosphere, land surface and the oceans. This article describes how ICOS fulfills its mission to harmonize these observations, ensure the related long-term financial commitments, provide easy access to well-documented and reproducible high-quality data and related protocols and tools for scientific studies, and deliver information and GHG-related products to stakeholders in society and policy.ISSN:0003-0007ISSN:1520-047

Organic Rankine Cycles including fluid selection

peer reviewedAn Organic Rankine Cycle (ORC) is similar to a steam Rankine cycle, except that the working fluid is not water but an organic compound, such as a refrigerant or a hydrocarbon, characterized by a lower ebullition temperature than that of water. Hence lower temperature heat sources can be exploited such as solar energy, geothermal energy and waste heat recovery from many different processes. During the design phase of an ORC system, the selection of the working fluid must be conducted in parallel with the selection and the sizing of the components (mainly the expansion machine, the pump and the heat exchangers) and with the definition of the cycle architecture. This approach allows taking into consideration all technical constraints. Relevant properties of working fluids that should be considered during their selection are listed. Major characteristics of available displacement and turbo-expander technologies are described. The impact of the pump performance on the overall performance is discussed and strategies to increase the available NPSH are proposed. Finally, improved cycle architectures are introduced. Major applications of ORC systems are described: geothermal power plants, biomass CHP plants, waste heat recovery in industry, waste heat recovery on internal combustion engines and solar power plants. All these applications differ by the nature of the heat source and heat sink, the integration of the ORC with these sources and sinks, and the range of installed capacities. These differences yield specific designs, which are described. Performance achieved by systems in operation or prototypes are presented

The Integrated Carbon Observation System in Europe

Since 1750, land use change and fossil fuel combustion has led to a 46 % increase in the atmospheric carbon dioxide (CO2) concentrations, causing global warming with substantial societal consequences. The Paris Agreement aims to limiting global temperature increases to well below 2°C above pre-industrial levels. Increasing levels of CO2 and other greenhouse gases (GHGs), such as methane (CH4) and nitrous oxide (N2O), in the atmosphere are the primary cause of climate change. Approximately half of the carbon emissions to the atmosphere is sequestered by ocean and land sinks, leading to ocean acidification but also slowing the rate of global warming. However, there are significant uncertainties in the future global warming scenarios due to uncertainties in the size, nature and stability of these sinks. Quantifying and monitoring the size and timing of natural sinks and the impact of climate change on ecosystems are important information to guide policy-makers’ decisions and strategies on reductions in emissions. Continuous, long-term observations are required to quantify GHG emissions, sinks, and their impacts on Earth systems. The Integrated Carbon Observation System (ICOS) was designed as the European in situ observation and information system to support science and society in their efforts to mitigate climate change. It provides standardized and open data currently from over 140 measurement stations across 12 European countries. The stations observe GHG concentrations in the atmosphere and carbon and GHG fluxes between the atmosphere, land surface and the oceans. This article describes how ICOS fulfills its mission to harmonize these observations, ensure the related long-term financial commitments, provide easy access to well-documented and reproducible high-quality data and related protocols and tools for scientific studies, and deliver information and GHG-related products to stakeholders in society and policy

Standards and Open Access are the ICOS Pillars: Reply to “Comments on ‘The Integrated Carbon Observation System in Europe’”

In his comment (Kowalski 2023) on our recent publication (Heiskanen et al. 2022) where we present the Integrated Carbon Observation System (ICOS) research infrastructure, Andrew Kowalski introduces three important and, in our opinion, different potential issues in the definition, collection, and availability of field measurements made by the ICOS network, and he proposes possible solutions to these issues