88 research outputs found

    Charge and proton dynamics in molecules and free clusters : from atomic to nanometer scale

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    The origin of properties in complex systems can often be traced to mechanisms involving charge and energy transfer in only a few embedded molecules. The detailed study of the time evolution of these mechanisms in their original environment is a challenging task. In this thesis we develop experimental tools and methods to enable the study of charge and energy transfer. A new ion and electron momentum imaging spectrometer, along with advanced data treatment methods has been succesfully designed, built and tested. The developed spectrometer is optimized for the measurement of the ion and electron momentum correlation that results from the fragmentation of complex systems, from molecules to molecular clusters.We have conducted photodissociation studies on such complex systems, using the newly developed experimental tools.The use of modern X-ray sources allows to localize the initial energy and charge to sites and/or elements in the system, from where the transfer is initiated.The energy and charge transfer is investigated in molecules by the local (multi-)photon absorption at a controlled site. Among other studies, we investigate the origin of the site-dependence of the fragmentation, be it the population of electronic excited states, conformational isomerization, fast hydrogen evaporation and migration, or secondary breakup. The influence of these processes on the fragmentation are investigated in two ways: through the C1s ionization of chemically distinct carbon sites (ethyl trifluoroacetate), and through the C1s excitation of a model system for conjugated (π) hydrocarbons (1,3 trans butadiene).The migration of charge and transfer of energy in embedded molecular systems is studied by the use of molecular clusters as model systems. The photo-induced energy and charge transport can be facilitated by intermolecular electronic decay, hydrogen migration, proton transfer, the Grotthus mechanism and nuclear rearrangement. The role of these processes in the stabilization and fragmentation of clusters is investigated in clusters of molecules containing N-H and O-H groups that form hydrogen bonds. Among other findings, we conclude that water is an effective stabilizer in multiply-charged hydrated ammonia clusters, which can play an important role in the nucleation process and photochemistry in atmospheric nanoparticles

    Ioonsete ja vesiniksidemetega molekulide fragmenteerumine sĂŒnkrotronkiirguse mĂ”jul

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    VĂ€itekirja elektrooniline versioon ei sisalda publikatsiooneSelles töös uuriti eksperimentaalselt ja arvutuslikult fragmenteerumisprotsesse ioonsetes ja vesiniksidemetega seotud molekulides. Uurimisobjektiks oli neli proovi: ioonne vedelik 1-etĂŒĂŒl-3-metĂŒĂŒlimidasoolium tetrafluoroboraat (EMImBF4) ja vesiniksidemetega seotud molekulaarsed klastrid atsetamiidist (CH3CONH2), atsetamiid-2,2,2-d3-st (CD3CONH2) ja ÀÀdikhappest (CH3COOH). Antud teadustöö esmĂ€rgiks oli uurida footoni energia mĂ”ju proovide stabiilsusele ja fragmenteerumismehhanismidele. Gaasfaasis olevate molekulide ioniseerimiseks kasutati sĂŒnkrotron- vĂ”i gaaslahenduslambi kiirgust vaakumultravioleti piirkonnas. KĂ”iki proove uuriti massispektromeetria abil, ioonne vedelik oli tĂ€iendavalt uuritud fotoelektronspektroskoopia abil. Erinevate fragmenteerumiskanalite energeetiliste omaduste vĂ€lja selgitamiseks mÔÔdeti ioonide osasaagised. NĂ€idati, et mĂ”lemad uuritud ĂŒhenditĂŒĂŒbid kipuvad ulatuslikult fragmenteeruma vaakumultravioletkiirguse mĂ”jul. Erinevad fragmenteerumismehhanismid olid vĂ€lja selgitatud ja mitmed sarnasused ioonse ja vesiniksidemetega seotud molekulaarsete sĂŒsteemide fragmenteerumisel vĂ€lja toodud. Olulise aspektina vĂ”ib vĂ€lja tuua, et erinevate fragmentatsioonikanalite esinemine ei sĂ”ltu mitte ainult footoni energiast, vaid on tugevalt mĂ”jutatud ka uuritava molekuli klasterisatsiooni tingimustest. Ă„Ă€dikhappe klastrite korral erinevad klasterisatsiooni tingimused pĂ”hjustasid erinevusi massispektrites. Sellest vĂ”ib jĂ€reldada, et fragmentatsiooni kanalid sĂ”ltuvad ka molekulide siseenergiast. Madalama siseenergiaga molekulaarsetes sĂŒsteemides on alla surutud aatomite ĂŒmberpaigutamisprotsessid, mille tulemusena vĂ”ivad tekkida uued fragmendid, kuna aatomite liikumist sĂŒsteemis ei toimunud. Selline kĂ€itumine oli iseloomulik madalama siseenergiaga ÀÀdikhappe trimeerile, mis fragmenteerus enne prootoni ĂŒlekannet vesiniksidemete lĂ”hkumisel, et moodustada dimeeri ioone. KĂ”rgematel siseenergiatel aga selline fragmentatsioonikanal puudus.In this work, we investigated experimentally and computationally the fragmentation processes of ionic and hydrogen-bonded molecules following valence photoionization. Four samples were studied: ionic 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) and hydrogen-bonded molecular clusters of acetamide (CH3CONH2), acetamide-2,2,2-d3 (CD3CONH2), and acetic acid (CH3COOH). The goal of the work was to investigate the influence of the photon energy on the stability of the samples and their fragmentation mechanisms. Tunable synchrotron radiation or gas discharge lamp radiation in the vacuum ultraviolet region was used to ionize the molecules in the gas phase. Clusters were studied by mass spectrometry, while ionic liquid was additionally studied by photoelectron spectroscopy. Partial ion yield technique was used to elucidate the energetics of various photofragmentation pathways. Both types of compounds were shown to be unstable toward near threshold ionization and therefore subjected to extensive fragmentation. Different fragmentation mechanisms were identified and common trends in dissociation behaviour of ionic and hydrogen-bonded compounds were observed. A significant finding is that not only photon energy influences the outcome of the valence ionization (at higher photon energy new fragmentation channels open up), but also the conditions at which the samples are introduced into the gas phase. In the case of acetic acid clusters, different clusterization conditions resulted in different mass spectra. A conclusion is drawn that photofragmentation channels of a molecule depend on its internal energy. Lower internal energy suppresses atomic rearrangements that might be required for a certain fragment formation and instead a new fragment is formed that does not require any rearrangement of the system. We observed such behaviour for acetic acid trimer that starts producing unprotonated dimers at stronger expansion conditions (lower internal energy), while there was no unprotonated dimers produced at weaker expansion conditions (higher internal energy)

    Fragmentation dynamics of ionised amino acids and neutral clusters of amino acids in the gas phase: a theoretical study

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    Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química. Fecha de lectura: 11-07-2017Esta tesis tiene embargado el acceso al texto completo hasta el 11-01-201

    Singlet Oxygen Oxidation of Guanine, 9-Methylguanine and Guanine-Cytosine Base Pair: Dynamics and Kinetics Revealed by Parallel Gas- and Solution-Phase Experiments and Computations

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    Singlet oxygen (1O2) oxidatively generated damage of DNA gives rise to mutagenesis, carcinogenesis, and cellular death. Guanine is the most susceptible DNA target of 1O2. The related process has been studied over three decades but the mechanism has remained elusive. My thesis research has focused on reaction mechanism, dynamics and kinetics of 1O2 oxidation of guanine, 9-methylguanine and guanine-cytosine base pair, from the gas-phase bare ions, through hydrated clusters, to aqueous solution. Various techniques have been adapted in the work, including 1O2 generation and detection, guided-ion beam tandem mass spectrometry, gas-phase ion-molecule scattering, and on-line spectroscopy and mass spectrometry measurement of solution kinetics. Experimental measurements, corroborated by electronic structure calculations, Rice-Ramsperger-Kassel-Marcus (RRKM) theory and direct dynamics trajectory simulations, have provided insights into the 1O2 oxidation chemistry of guanine. Four projects have been completed, and each of which is described below. In the first project, ion-molecule scattering mass spectrometry was utilized to capture unstable endoperoxides in the collisions of hydrated guanine ions (protonated or deprotonated) with 1O2 at ambient temperature. Theoretical calculations have strongly supported an intermediate structure of 5,8-endoperoxide rather than 4,8-endoperoxide was proposed in literature. Protonation and deprotonation of reactants in the gas phase, vis-Ă -vis acidic and basic media in solution reactions, lead to different oxidation chemistries starting from initial stage. This project has pieced together reaction mechanisms and dynamics data concerning the early stage of 1O2 induced guanine oxidation, which is missing from conventional condensed-phase studies. In the second experiment of this thesis, gas-phase dry and monohydrated 9-methylguanine (9MG) was utilized as a model compound to examine the early stage oxidation mechanism and dynamics of the guanine nucleoside. Different levels of theory, including Multi-referential CASSCF and CASMP2, were applied for a reliable description of the early-stage reaction potential surface (PES). The oxidation of protonated 9MG is initiated by the formation of a 5,8-endoperoxide via a concerted cycloaddition as protonated guanine. In contrast, the initial stage of deprotonated 9MG oxidation switches to an addition of O2 to the C8 position only. The comparison between the 1O2 oxidation of ionized guanine and 9-methylguanine indicates that the N9-substitution not only affects the reaction mechanism but inhibits the reactivity of guanine toward 1O2. In the third project, a solution-phase kinetic and mechanistic study of 1O2 oxidation of guanine and 9MG was examined at pH 3.0, 7.0 and 10.0, respectively. Oxidation products and the branching ratio were determined, with each structure inferred from collision-induced dissociation (CID) mass spectra. In basic and neutral solutions, the oxidation products of guanine and 9MG are dominated by spiroiminodihydantoin (Sp), whereas in acidic solution guanidinohydantoin (Gh) is the favored product, showing strong pH dependence of oxidation. gem-diol intermediate, which serves as the precursor for the formation of Gh, was detected. On the basis of solution compositions at each pH, first-order rate constants for individual oxidizable species were extracted. That is 3.2 - 3.6 ÂŽ 106 M-1∙s-1 for deprotonated guanine, 1.1 ÂŽ 106 and 4.6 - 4.9 ÂŽ 107 M-1∙s-1 for neutral and deprotonated 9MG, respectively. Guided by density functional theory-calculated reaction potential energy surfaces, transition state theory (TST) was applied to evaluate the kinetics of the 1O2 addition to guanine and 9MG. The comparison of TST predictions with experiment assures that initial 1O2 addition is the rate-limiting for oxidation, and all of the end products evolve from ensuring endoperoxides and/or peroxides which form at an efficiency of ÂŁ 2.5% based on previous measurements of the same systems in the gas phase. In the last project, an experimental and trajectory study was reported, focusing on the 1O2 oxidation of gas-phase deprotonated guanine-cytosine base pair [G·C – H]– that is composed of 9HG·[C – H]– and 7HG·[C – H]– (pairing 9H- or 7H-guanine with N1-deprotonated cytosine), and 9HG·[C – H]–_PT and 7HG·[C – H]–_PT (formed by intra-base-pair proton transfer from guanine N1 to the N3 of [C – H]–). Guided-ion-beam mass spectrometry was used to measure the conformer-averaged product and cross section for [G·C – H]– + 1O2. 1O2 collision dynamics with each of the four conformers was simulated at B3LYP/6-31G(d), to explicate conformation-specific reactivities and changes upon and after oxidation. Trajectories showed that 9HG-containing base pairs favor stepwise formation of 4,8-endoperoxide of guanine, whereas 7HG-containing base pairs prefer concerted formation of guanine 5,8-endoperoxide. Oxidation entangles with intra-base-pair proton transfer, and prefers to occur during the time when the base pair adopts a proton-transferred structure. Guided by trajectories, reaction PESs were established using spin-projected density functional theory. PESs indicate that proton-transferred base-pair conformers have lower barriers for oxidation than non-proton-transferred counterparts

    Explicit influence of water microsolvation on charge transfer and dynamics in ground and excited electronic states of molecular systems

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    Modern computational molecular quantum chemical studies, such as the present one, typically employ a wide range of theoretical techniques. The latter are often rather complicated and one should not generally expect that an experimental scientist in the area of physical chemistry, a potential reader of this work, should be familiar with all these techniques. To simplify the reading of the Thesis and to make it self-sufficient, it is supplied with an overview of the employed theoretical methodologies (Chapter 1). The overview explains basic quantum-chemical terminology referred to throughout the Thesis, introduces theoretical foundations of the methods and outlines their properties and limitations. In Part 1.1 of Chapter 1, methods for the solution of the molecular Schrödinger equation are introduced, while in the subsequent Parts 1.2 and 1.3 methods for the solution of the electronic Schrödinger equation are presented to find the ground and excited states, respectively. Part 1.4 is dedicated to basis-set effects which are omnipresent in electronic-structure calculations. It contains a number of unusual insights and concepts proposed by the author and, thus, may be insightful also to experts in quantum chemistry. In Chapter 2, the phenomenon of acetone-water proton exchange catalyzed by tubular as well as amorphous aggregates of calix[4]hydroquinone (CHQ) macromolecules, which has been observed previously in NMR experiments (Ref. D1D), is investigated by means of correlated quantum-chemical methods. The first part of the study (Section 2.3-2.7) considers concerted proton transfer, assisted by several initially neutral OH-groups in the hydrogen-bonded networks of CHQ aggregates. The second part of the study (Section 2.8-2.13) is dedicated to a second mechanism of proton exchange: step-wise proton transfer via formation of ionic intermediates resulting from CHQ pre-dissociation. CHQ application-specific as well as general conclusions, relevant to the main topic of the Thesis (i.e. influence of specific microsolvation on the considered proton transfer processes), are presented in Section 2.14. The phenomenon of dual fluorescence observed in clusters of methyl 4-N,N-dimethylaminobenzoate ester (DMABME) and two water molecules in the gas phase, is studied in Chapter 3. Experimentally, the dual fluorescence was detected in experiments combining optical and ground-state ion-depletion infrared spectroscopies in ultracold molecular beams (Ref. D2D). In Section 3.3, calculated ground-state infrared spectra are presented that allow to identify the structures of those isomers, which are present in the gas-phase, as well as the structure of the isomer responsible for dual fluorescence. To further understand the reaction mechanism of dual fluorescence, excited-state potential energy surfaces of the identified isomers were computed along the relevant twisted intermolecular charge-transfer formation coordinate and the mechanism of energy dissipation in these complexes was investigated (Section 3.4-3.5) (Ref. D3D). A brief summary of the main results of this chapter and conclusions are given in Section 3.6. Finally, in Section 3.7 a complementary benchmark study of the quality of ground-state potential energy surfaces of prototypical hydrogen-bonded systems (ammonia-water and formic acid-water dimers) obtained at the level of BSSE-corrected MP2 combined with moderate basis sets, has been conducted. The quality of potential energy surfaces was tested with respect to basis-set size, level of electron correlation and anharmonicity effects and the applied methodology to identify the IR spectrum of hydrated DMABME complexes (Section 3.3) has been found to be sufficient to uniquely assign the IR spectra.Moderne computergestĂŒtzte molekulare quantenchemische Studien, wie die vorliegende, verwenden in der Regel ein breites Spektrum theoretischer Methoden. Die letzteren sind oft sehr komplex und man sollte generell nicht erwarten, dass ein praxisorientierter Wissenschaftler im Bereich der physikalischen Chemie – ein potentieller Leser dieser Arbeit – mit all diesen Methoden vertraut sein muß. Um das Lesen dieser Dissertation in einem solchen Fall zu vereinfachen, und sie autark zu machen, ist sie mit einem Überblick ĂŒber die verwendeten theoretischen Methodologien versehen (Kapitel 1). In diesem Überblick werden quantenchemische Grundbegriffe erlĂ€utert, auf die in der gesamten Arbeit immer wieder verwiesen wird, die theoretischen Grundlagen verwendeter Methoden dargelegt und deren Eigenschaften und BeschrĂ€nkungen skizziert. Im Abschnitt 1.1 werden allgemeine AnsĂ€tze zur Lösung der molekularen Schrödingergleichung eingefĂŒhrt, und in den Teilen 1.2 und 1.3 werden spezifische AnsĂ€tze zur Lösung der elektronischen Schrödingergleichung zur Bestimmung des elektronischen Grundzustands und angeregter ZustĂ€nde prĂ€sentiert. Teil 1.4 ist der Beschreibung von Basissatzeffekten, die in Elektronenstrukturrechnungen im Allgemeinen auftreten, gewidmet. Dieser Abschnitt enthĂ€lt eine Reihe von verschiedenen Einblicken und Konzepten, die im Rahmen dieser Arbeit vorgeschlagen werden, und welche den Experten in der Quantenchemie aufschlußreich sein können. Im Kapitel 2 wird das PhĂ€nomen der Katalyse von Aceton-Wasser Protonenaustausch durch selbstaggregierende Calix[4]hydrochinon (CHQ)-Nanotubes sowie durch amorphe Aggregate von CHQ, welche in NMR-Versuchen (Ref. X1X) beobachtet wurde, mit Hilfe von modernen quantenchemischen Methoden untersucht. Der erste Teil dieser Studie (Abschnitt 2.3-2.7) betrachtet den konzertierten Protonentransfer, unterstĂŒtzt von mehreren ursprĂŒnglich neutralen OH-Gruppen innerhalb der wasserstoffgebundenen Netzwerke der CHQ-Aggregate. Der zweite Teil der Studie (Abschnitt 2.8-2.13) ist dem dem schrittweisen Protonentransfer mittels Bildung von ionischen Zwischenprodukten infolge der CHQ- PrĂ€dissoziation gewidmet. CHQ-anwendungsspezifische Schlußfolgerungen, sowie allgemeine Aspekte, die fĂŒr das Hauptthema dieser Dissertation relevant sind (i.e. Einfluß spezifischer Mikrosolvatation auf die betrachteten Protonentransferprozesse), werden im Abschnitt 2.1.4 zusammengefasst. Das PhĂ€nomen der dualen Fluoreszenz, das in Komplexen von 4-N,N-DimethylaminobenzoesĂ€uremethylester (DMABME) und zwei WassermolekĂŒlen in der Gasphase beobachtet wurde, wird im Kapitel 3 untersucht. Im Abschnitt 3.3 werden zunĂ€chst berechnete Grundzustandsinfrarotspektren verschiedener DMABME*2H2O Isomere prĂ€sentiert, die zum einen die Identifikation aller in der Gasphase vorliegenden Isomeren erlauben, und zum anderen vor allem die Charakterisierung des fĂŒr das Auftreten der dualen Fluoreszenz verantwortlichen Isomer ermöglichen. Um weiter den Reaktionsmechanismus der dualen Fluoreszenz zu verstehen, wurden die PotentialenergieflĂ€chen der relevanten Isomere im angeregten Zustand entlang der sogenannten TICT-Koordinate (TICT: engl. twisted intramolecular charge transfer) berechnet und der Mechanismus der Energierelaxation dieser Komplexe erforscht (Abschnitt 3.4-3.5) (Ref. X3X). Eine kurze Zusammenfassung der wichtigsten Ergebnisse dieses Kapitels und die wichtigsten Schlußfolgerungen finden sich in Abschnitt 3.6. Zum Abschluß wird im Abschnitt 3.7 eine Vergleichsstudie der QualitĂ€t der PotentialenergieflĂ€chen von prototypischen wasserstoffgebundenen Systemen im elektronischen Grundzustand (Ammoniak-Wasser und AmeisensĂ€ure-Wasser) zusammengefasst, in der die QualitĂ€t der PotentialenergieflĂ€chen hinsichtlich des verwendeten atomaren Basissatzes, der Behandlung der Elektronenkorrelation und der AnharmonizitĂ€t der PotentialflĂ€chen getestet werden. Vor allem wurde festgestellt, dass die zum Studium der IR-Spektren der hydratisierten DMABME-Komplexe verwendete Methode hinreichend genau ist, um die einzelnen Isomere zu unterscheiden und die experimentellen Spektren eindeutig zuzuordnen (Abschnitt 3.3)

    Disentangling the Vibrational Spectra of Water with Cryogenic Water Clusters: from Isolated Static OH Oscillator to Temperature Dependent Spectral Dynamics

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    Water is arguably the most important solvent and reactant on earth. It has many special properties compare to other liquids thanks to its hydrogen bonding. Understanding the interaction between water molecules as well as with other solutes in aqueous solutions is of great importance for studying reactions that happens in aqueous environments. Water in its many forms is heavily investigated by many experimental and theoretical methods including rotational, vibrational and electronic spectroscopy, ultrafast spectroscopy, interface specific spectroscopy, neutron scattering, X-ray diffraction, atomic force microscopy, mass spectrometry, nuclear magnetic resonance spectroscopy and so on. With improvements in instrumentation and computation power, our knowledge of water’s special properties keeps advancing toward a more accurate molecular level understanding. Among the experimental techniques, vibrational spectroscopy is widely used in several variations including linear absorption spectroscopy, ultrafast multidimensional spectroscopy, and interface specific spectroscopy, among others. The advantage of using vibrational spectroscopy to study water is its sensitivity towards structural information as well as relatively high time resolution. Linear absorption spectroscopy is the most common ways of studying isolated water clusters in the gas phase and provides highly resolved fundamental frequencies that are useful for theoretical calibration. The non-linear methods are mostly used in the condense phase to provide structural and dynamical information about water and aqueous systems. However, these approaches each have their own limitations. For the traditional cluster study, the cluster size are usually small and the hydrogen bond environments are less complex compared to those in the condense phase. Several studies of very large water cluster run into another problem, where the large number of overlapping bands masks detailed structural information about the OH oscillators. The condense phase study suffers from a similar problem, where even with isotopic dilution, many thousands of oscillators are sampled every time. Hence, it is impossible with the current experimental sensitivity in the condense phase to isolate a single water molecule’s spectral feature and information about its specific hydrogen bond environment. In this thesis, I report new experiments that tracks single OH oscillators or single intact water molecules imbedded in an extended hydrogen bond network made of D2O molecules. Such experiment allowed unprecedented molecular level insight into the OH spectral mechanics including hydrogen bond environment’s effect on the OH frequency as well as linewidth up to the second hydration shell, the intra- and intermolecular couplings, and Fermi resonances. After establishing the correlation between the OH frequency and the structural information, a new type of experiment was developed to observe spectral diffusion inside a water cluster via water reorientation. Various pathways were activated at different temperatures, which display different rate constants, and hence allowing the determination of activation energy of each pathway. Together with the OH frequency of interest, detailed reorientation pathway can be inferred to reveal what type of water molecules are involved in the H-bond rearrangement. It was observed that the water molecule at the surface of the cluster starts to move first at lower temperature which resembles the surface melting phenomena

    Determining the dominant degradation mechanisms in Nitrocellulose

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    Nitrocellulose (NC) is the base component for many modern day propellants and explosives, as well as for everyday items such as printing inks, paint and lacquer coatings. Despite its early beginnings as the first man-made plastic, the decomposition pathways from the bulk material to the products observed from its ambient ageing are still not fully understood. Knowledge of these processes are of critical importance when considering the conservation of NC artefacts, refinement of product formulations, predictions of shelf life and safety improvements. In this study, the dominant degradation pathways of NC were investigated using quantum mechanics (QM) methods to probe the mechanisms leading to the initial cleavage of nitrate groups from the cellulosic backbone. The NC structure was truncated from a polymer chain to monomer, dimer and trimer units. Density functional theory methods (DFT) were used to study the mechanistic detail at individual nitrate sites. Comparison of differently sized units using the quantum theory of atoms in molecules (QTAIM), analysis of the electrostatic potential (ESP) surface and partial charges showed that the most suitable approximation for study of the decomposition reactions was the ÎČ-glucopyranose monomer, bi-capped with methoxy groups. The primary thermolytic and hydrolytic denitration routes were explored using transition state (TS) searches and potential energy surface (PES) scans. It was found that the thermolytic behaviour of the NC denitration step matched that of a well studied nitrate ester, pentaerythritol tetranitrate (PETN). The hydrolytic scheme for nitrate cleavage was studied, finding that protonation at the bridging oxygen site was the most likely to lead to denitration. It was not possible to isolate a TS for the hydrolytic reaction, though a number of coordination schemes were tested. Key secondary processes beyond nitrate cleavage were examined to determine the fate of nitrogen in the system and the cause of the transition from a first order reaction rate to autocatalytic decomposition. The energies of reactions in three different decomposition schemes proposed in literature were compared. Ethyl nitrate was used as a test system before extension to the NC monomer. New reaction pathways for decomposition were constructed using the reactions posed in the literature studies. The new schemes revealed that ‱NO2 was the most likely cause for the experimentally observed autocatalytic rate of degradation

    Attosecond spectroscopy of bio-chemically relevant molecules

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    Understanding the role of the electron dynamics in the photochemistry of bio-chemically relevant molecules is key to getting access to the fundamental physical processes leading to damage, mutation and, more generally, to the alteration of the final biological functions. Sudden ionization of a large molecule has been proven to activate a sub-femtosecond charge flow throughout the molecular backbone, purely guided by electronic coherences, which could ultimately affect the photochemical response of the molecule at later times. We can follow this ultrafast charge flow in real time by exploiting the extreme time resolution provided by attosecond light sources. In this work recent advances in attosecond molecular physics are presented with particular focus on the investigation of bio-relevant molecules
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