Light actinides and copper systems were studied using resonant soft X-ray spectroscopy. An instrumental and experimental setup for soft X-ray spectroscopy meeting the requirements of a closed source for radioactivity was developed and described in detail. The setup was used for studies of single-crystal PuO2 oxidation. The existence of higher oxidation state than Pu(IV) in some surface areas of the single crystal were found from O 1s X-ray absorption measurements. Furthermore, from comparison with first principles calculations it was indicated that plutonium oxide with Pu fraction in a higher oxidation state than Pu(IV) consists of inequivalent sites with Pu(IV)O2 and Pu(V)O2 rather than a system where the Pu oxidation state is constantly fluctuating between Pu(IV) an Pu(V). It was shown that a combination of resonant O Kα X-ray emission and O 1s X-ray absorption spectroscopies can be used to study electron correlation effects in light-actinide dioxides. The electronic structure of copper systems was studied using resonant inelastic soft X-ray scattering and absorption spectroscopy. It was found that X-ray absorption can be used to monitor changes in the oxidation state but as differences between systems with the same oxidation state are in many cases small, speciation is uncertain. Therefore, a method utilizing resonant inelastic X-ray scattering as fingerprint to characterize complex copper systems was developed. The data recorded at certain excitation energies revealed unambiguous spectral fingerprints for different divalent copper systems. These specific spectral fingerprints were then used to study copper films exposed to different solutions. In particular, it was shown that resonant inelastic X-ray scattering can be used in situ to distinguish between CuO and Cu(OH)2, which is difficult with other techniques.

<p>Dissociative recombination (DR) is a process in which a positive molecular ion recombines with an electron and subsequently dissociates into neutral fragments. Among the different types of molecular ion-electron reactions DR deserves particular attention due to the important role it plays in low-temperature and low-density plasmas. Despite the apparent simplicity of the DR reaction, its investigation has proven to be a difficult task from both experimental and theoretical perspectives. In order to shed more light upon this process the storage ring technique has been introduced and utilised extensively for the last few decades. This thesis is devoted to experimental studies into the DR reaction at the storage ring CRYRING. The DR reaction has been investigated for the following molecular ions; Na⁺(D₂O), PD₂⁺, O₃⁺, N₃⁺, H₂⁺, D₂H⁺, OPCl⁺, OPCl₂⁺ and H₃O⁺, with the aim to ascertain rotational state effects, to find patterns in the branching products of similar molecular ions, to investigate isotope effects and to study in detail the dynamics involved in the three-body break-up channel.</p>

Dissociative recombination (DR) is a process in which a positive molecular ion recombines with an electron and subsequently dissociates into neutral fragments. Among the different types of molecular ion-electron reactions DR deserves particular attention due to the important role it plays in low-temperature and low-density plasmas. Despite the apparent simplicity of the DR reaction, its investigation has proven to be a difficult task from both experimental and theoretical perspectives. In order to shed more light upon this process the storage ring technique has been introduced and utilised extensively for the last few decades. This thesis is devoted to experimental studies into the DR reaction at the storage ring CRYRING. The DR reaction has been investigated for the following molecular ions; Na+(D2O), PD2+, O3+, N3+, H2+, D2H+, OPCl+, OPCl2+ and H3O+, with the aim to ascertain rotational state effects, to find patterns in the branching products of similar molecular ions, to investigate isotope effects and to study in detail the dynamics involved in the three-body break-up channel.

We have constructed a compact purely electrostatic ion-beam trap, ConeTrap, which we have mounted inside a double-walled vacuum chamber. In the inner vacuum chamber, we can obtain ultra-high vacuum (UHV) conditions and reach thermal equilibrium at well controlled temperatures down to 10 K. The chamber was constructed partly with the purpose of making high-precision measurements in ConeTrap, but also as a test-chamber for testing components (such as the detector-assembly tested and described in this thesis and paper III) to be used in the DESIREE (Double ElectroStatic Ion Ring ExpEriment) facility. The latter is a double electrostatic ion storage-ring being constructed at Stockholm University, in which the conditions are meant to mimic the environment in the interstellar medium. The interaction between two oppositely charged ions at very low relative velocities (controlled collision energies down to 10 meV) may then be studied in a section of the storage device where the two ion beams merge. The lifetime of loosely bound electronic systems, for example He-, is, at room temperature (and even at much lower temperatures), significantly affected by photons from blackbody radiation from the experimental device and its surroundings. The cryogenic temperature and low pressure obtained in the test chamber have made it possible to use ConeTrap to make the first correction-free lifetime measurement of the long-lived J=5/2 fine-structure level of the metastable 1s2s2p 4Po state of He-. Under the assumption of a statistical population of the fine-structure levels, at the time when the ions are created, we have also deduced the lifetimes of the short-lived J=1/2 and J=3/2 fine-structure levels. Furthermore, we have used ConeTrap to measure the pressure dependent storage lifetimes of He+ and Ar+ ions over wide ranges of temperatures and pressures, and we have thus been able to store positive ions with storage lifetimes of tens of seconds. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted.

A Vernier spectrometer is built with a near-infrared mode-locked Er:doped fiber laser, a Fabry-Perot cavity with finesse of 1000, a diffraction grating and a photo detector. The optical cavity provides high sensitivity in absorption detection by enhancing the interaction length of the light with molecular species contained in the cavity. Coupling an optical frequency comb to the cavity provided a broadband spectral bandwidth with high precision to measure the absorption of several molecular species simultaneously. Also, by using the optical cavity as a filter, transmission of some bunch comb lines was achieved. This comb filtering together with a simple grating and a photodiode formed the Vernier detection technique to provide very fast measurements while it kept the setup very simple and compact. The system allows to detect carbon dioxide in the air and water vapor and OH radicals in the flame in a spectrum spanning from 1550 nm to 1590 nm, approximately. The retrieved spectrum has a resolution of 9.3 GHz being acquired in 0.05 s.

A common consequence of protein denaturation is the loss of biological activity. Natural osmolytes such as Trimethylamine N-oxide (TMAO) contribute to protein folding, whereas other osmolytes such as urea act as an agent in the denaturation of proteins. Many studies have shown that denaturation of proteins could occur for certain concentrations of urea, however, this effect could be prevented with the presence of Trimethylamine N-oxide (TMAO) molecules. The aim of the present study is to find out the mechanism of TMAO as a protein stabilizer against urea. Firstly, Molecular Dynamics simulations were carried out for 1, 8, 27 and 64 TMAO molecules. The time-average location of the TMAO molecules during the simulation was studied by the partial density. These simulations examine if TMAO is amphiphilic molecule, i.e contains both hydrophobic and hydrophilic parts. However, these results might not be representative due to bad statistics. Secondly, an experiment ran at BESSY II at Helmholtz-Zentrum Berlin using X-ray Photoelectron Spectroscopy in liquids. In this experiment, Lauryldimethylamine oxide(LDAO) was used instead of Trimethylamine N-oxide (TMAO) due to some practical reasons. The behaviour of urea and LDAO molecule was studied when these molecules were in different and same solutions. The purpose of this experiment is to find out the mechanism of LDAO against urea. Finally, LDAO interacts with urea and a possible mechanism between them is suggested. A common consequence of protein denaturation is the loss of biological activity. Natural osmolytes such as Trimethylamine N-oxide (TMAO) contribute to protein folding, whereas other osmolytes such as urea act as an agent in the denaturation of proteins. Many studies have shown that denaturation of proteins could occur for certain concentrations of urea, however, this effect could be prevented with the presence of the Trimethylamine N-oxide (TMAO) molecules. The aim of the present study is to find out the mechanism of TMAO as a protein stabilizer against urea. Firstly, Molecular Dynamics simulations were carried out for 1, 8, 27 and 64 TMAO molecules. The time-average location of TMAO molecules during the simulation was studied by the partial density. These simulations examine if TMAO is amphiphilic molecule, i.e contains both hydrophobic and hydrophilic parts. However, these results might not be representative due to bad statistics. Secondly, an experiment ran at BESSY II at Helmholtz-Zentrum Berlin using X-ray Photoelectron Spectroscopy in liquids. In this experiment, Lauryldimethylamine oxide (LDAO) was used instead of Trimethylamine N-oxide (TMAO) due to some practical reasons. The behaviour of urea and LDAO molecule was studied when these molecules were in different and same solutions. The purpose of this experiment is to find out the mechanism of LDAO against urea. Finally, LDAO interacts with urea and a possible mechanism between them is suggested. / <p></p><p></p><p></p><p></p><p></p><p></p><p></p><p></p><p></p><p></p><p></p>

Since the surprising first detection of small carbon cluster dianions by Compton et al 1990, several studies have been made investigating their structure, fragmentation pathways and stability. As other carbon anions have been found in space, it is likely that these dianions exists as well and their ability to react with other molecules is therefore of interest. Previous studies have shown that they may survive on microsecond timescales, but it is still an open question whether they are metastable or thermodynamically stable. Therefore, this study utilizes the cyrogenic storage ring DESIREE to investigate the lifetime and stability of carbon cluster dianions Cn(2-) (n=7-10) in the new domains. Dianions were produced with a cesium ion sputtering source and their spontaneous decay Cn(2-) -&gt; Cn(-) + e- was monitored for almost 100 ms by detection of the singly charged decay products. Also, the extra electron's tunneling probability through the repulsive coloumb barrier for C8(2-) was calculated and the lifetime for different energy states was estimated. Analyzing the DESIREE data, the lifetime of the dianions could be determined to exceed the previous concluded lifetimes of 10 us by a whole order of magnitude. The only way to detect stable ions after that would be if they collided with rest gas and due to good vacuum, this eventual signal is too low. Probably due to varying structures, an alternating pattern was found, dianions with even n decaying slower than their odd neighbours. The fitting of power laws to the data is consistent with that the dianions were produced with a broad internal energy distribution. Calculations for C8(2-) indicated that its electron affinity had to be at least -1eV in order to agree with the experimental results. Continuing the investigations, future studies could, after sufficient time, use DESIREE in an alternative way, allowing detection of possible stable dianions.

No description available.

Cavity enhanced optical frequency comb spectroscopy is a technique that allows for quick and sensitive measurements of molecular absorption spectra. Locking the comb lines of an optical frequency comb to the cavity modes of an enhancement cavity and then extracting the spectral information with a Fourier transform spectrometer grants easy access to wide segments of absorption spectra. One of the main obstacles complicating the analysis of the measurements is the inevitable dispersion occurring inside the cavity. In this project, absorption measurements of CO2 were performed using an existing and well established setup consisting of a near-infrared optical frequency comb locked to a Fabry- Pérot enhancement cavity using the Pound-Drever-Hall technique, and a Fourier transform spectrometer. The purpose was to improve theoretical models of the measured absorption spectra by creating and verifying a model for the cavity dispersion, stemming mostly from the cavity mirrors but also from the normal dispersion of the intracavity medium. Until now, the cavity dispersion has been treated as an unknown and was included as a fitting parameter together with the CO2 concentration when applying fits to the absorption measurements. The dispersion model was based on previously performed precise measurements of the positions of the cavity modes. The model was found to agree well with measurements. In addition, pre-calculating the dispersion drastically reduced computation time and seemed to improve the overall robustness of the fitting routine. A complicating factor was found to be small discrepancies between the locking frequencies as determined prior to the measurements and the values yielding optimum agreement with the model. These apparent shifts of the locking points were found to have a systematic dependence on the distance between the locking points. The exact cause of this was not determined but the results indicate that with the locking points separated by more than about 10nm the shifts are negligible.

Multilayered interference coatings based on titanium- and zirconium nitride and designed for solar control have been prepared using reactive d c magnetron sputtering. Preparation effects and degradation mechanisms were investigated. It was shown that the quality of the nitride strongly depends on the degree of crystallinity in the underlying oxide. It has been shown that the nitride layer partly oxidizes as the top oxide layer is deposited. The degradation is enhanced with temperature. A thin sacrificial layer of aluminium deposited between successive depositions of nitride and oxide is shown to improve the optical performance of the coating as preparedm as well as after accelerated ageing tests. The optical properties of opaque and semitransparent films of zirconium nitride have been studied. A thorough investigation of the influence of composition, deposition rate, substrate temperature and film thickness on the optical response of the film was performed. Both photometric and ellipsometric methods were used to determine thicknesses and the optical constants at wavelengths ranging from 0.23 to 25 μm. The resulting values of n and k, in the wavelength intervals where these independent methods are applicable, have been shown to agree extremely well. The results so far indicate an even larger potential for zirconium nitride based solar control coatings as compared to the titanium nitride based. Access to optical constants derived from films of zirconium nitride of variable quality made multilayer modelling a powerful tool in the design and analysis of solar control coatings.