Quantum Chromodynamics (QCD) is the theory of the strong interaction, one of the fundamental forces of nature. The interactions between quarks are mediated by gluons, which are the colour-charged gauge fields in QCD. Hard processes with a large momentum transfer can be calculated using perturbation theory, while soft processes with a small momentum transfer are poorly understood. In this thesis, various aspects of the gluon interactions are studied based on the interplay between hard and soft processes. Soft gluon exchanges do not affect the dynamics of a hard process, but can rearrange the colour topology, resulting in different final states. The soft colour interaction models employ this idea and give a good description of all diffractive hard scattering data observed in pp collisions (W, Z, dijets, bb, J/ψ). This thesis also presents predictions for diffractive Higgs and γγ production at present and future hadron colliders. Multiple gluon exchanges give rise to saturation effects in hadronic collisions at high energies. Implementing this idea in photon-photon collisions gives new insight into the quantum structure of the photon and its interactions at high energies. When combined with perturbative calculations for single gluon exchange, the obtained results are in good agreement with experimental data from e+e- colliders. Off-shell gluon distributions in the photon give another perspective on the photon structure and have been parameterized for the first time in this thesis. These are useful for calculating cross sections of processes where the effects of transverse momenta are crucial, for example heavy quark production in γp or γγ collisions. Quantization of gauge fields which have a richer gauge structure than the gluons in QCD, is studied using the powerful BRST quantization formalism. Thus, first-stage reducible theories, like topological Yang-Mills and spin-5/2 gauge fields, are successfully quantized in an irreducible way. Understanding gluon interactions and the interplay between soft and hard processes paves the way towards solving the longstanding problem of confinement in QCD.

Protein-surfactant interactions in aqueous media have been investigated. The globular proteins lysozyme and bovine serum albumin (BSA) served as model proteins. Several ionic and non-ionic surfactants were used. Fluorescence probe measurements showed that at low sodium dodecyl sulfate (SDS) concentration (< 0.1 M) one micelle-like SDS cluster is bound to lysozyme. From dynamic light scattering (DLS) results it was observed that lysozyme in the complex does not correspond to the fully unfolded protein. At high SDS concentration (> 0.1 M) one compact and one more extended lysozyme-SDS complex coexist. The influence of surfactant alkyl chain length and headgroup on BSA-surfactant complex formation was investigated. In these studies, binding isotherms were determined by nuclear magnetic resonance (NMR), DLS was used to measure the hydrodynamic radii of the complexes and the size of the micelle-like aggregates on BSA was determined using fluorescence probe methods. It was observed from fluorescence measurements that the number of bound SDS molecules does not depend on the presence of the disulfide bridges. Reduced proteins wrap more efficiently around the micelle-like structures, resulting in somewhat smaller complexes, as observed with DLS. Concentrated BSA-SDS solutions and the corresponding heat-set gels were investigated using DLS and fluorescence probe methods. Correlation lengths in the gel were determined and it was concluded that SDS forms micelle-like aggregates on BSA in concentrated solution and gel phase. The gel region in the ternary phase diagram BSA-SDS-3.1 mM NaN3 has been determined at room temperature.

This thesis concerns electron transfer reactions from different excited states in porphyrins, and the effect of changing the energy of the link connecting the donor and acceptor. Photoinduced electron transfer, and subsequent processes were studied using ultrashort laser pulses and nanosecond laser flash photolysis. Excitation of Zn(II)-porphyrins in the Soret band lead to population of the higher lying S2 state. The lifetime and transient absorption spectrum was measured for the S2 state. When an electron acceptor was attached to the Zn(II)-porphyrin, either as an ion pair, or covalently bound through an amide link, electron transfer was found to compete with S2 to S1 relaxation. In the ion pair, electron transfer was faster than 200 fs, with a lifetime of the charge separated state of 1.3 ps. Further, in the covalently linked dyad, the Zn(II) porphyrin triplet state was repopulated from a charge transfer state. In [2]-rotaxanes, the Zn(II) porphyrin donor (ZnP) and Au(III) porphyrin acceptor (AuP+) are not connected by a direct covalent link. Selective excitation of either the ZnP or the AuP+ resulted in rapid electron transfer from the ZnP to the AuP+. The bis-phenanthroline link connecting the. different porphyrins was changed by coordination of Cu(I) or Ag(I). Electron transfer from the 1ZnP singlet was unaffected by coordination of either Ag(I) or Cu(I), while electron transfer to the 3AuP+ triplet was in the Ag(I) link found to occur by an enhanced superexchange, and by a sequential mechanism in the Cu(I) coordinated link.

Mössbauer spectroscopy has been used as a powerful tool to investigate the local properties of some materials suitable as active ingredients in technological applications. The magnetic properties of some magnetic multilayers were investigated using conversion electron Mössbauer spectroscopy. The interface quality of Fe/V(001) multilayers was determined by measuring the hyperfine magnetic field distributions. The wide distributions found were a sign of interface roughness of the order of at least 2 monolayers. Influence of the interlayer exchange coupling was also apparent. In Fe/Co(001) multilayers three different hyperfine field components belonging to interface, interface near and bulk layers could be resolved. The easy axis of magnetisation could also be deduced to be [110]. In a study of a Fe/ZnSe heterostructure, no interface diffusion could be seen for the Fe/ZnSe(001) interface. Thus enabling a high interface polarisation, which is necessary for spin polarised tunnelling. Furthermore a complicated magnetic anisotropy situation was found where the iron layers closest to the interface had magnetic moments pointing along [110] while the rest of the iron moments were aligned along [100]. Lithium ion cells with η '-Cu6Sn5 and SnB2O4-glass as anodes were investigated using 119Sn Mössbauer spectroscopy in situ during charge and discharge. The compounds formed after lithium-intercalation could thereby be established. In both cells the lithiation resulted in lithium alloying with tin to a maximum composition of Li4.4Sn. It had, however, different implications for the capacity of the cells. Finally, electrochromic SnO films were investigated using 119Sn Mössbauer spectroscopy. The electrochromism could be ascribed to the valence-state change from Sn(IV) to Sn(II) inside the films.

This thesis addresses the electronic and geometric structures of fullerene based transition-metal compounds and other related systems. The formation of TixC60, VxC60 and NbxC60 compounds has been examined by X-ray photoelectron, soft X-ray absorption and emission and spectroscopy techniques, including resonant inelastic X-ray scattering (RIXS). The symmetry and character of the chemical bond of transition metal-fulleride has been determined. A related study of single-walled carbon nanotubes is also presented. The experimental results are compared to predictions based on calculation within a C60Tix(x=1, 2) cluster model using gradient corrected density functional theory. Good agreement between theory and experiment is found with the Ti metal atom coordinated to the six-ring site. The formation of transition metal fullerides is due to hybridization between the orbitals of the transition metal atoms and the C60 orbitals, and the RIXS spectra at the C K edge reveals the symmetry of the chemical bond. X-ray emission spectra of VxC60 and NbxC60 are similar to that of TixC60, suggesting that the chemical bond has the same symmetry in these compounds. These results indicate that the RIXS method provides an excellent basis for the probing of the bonding between metals and organic molecules. Non-resonantly excited X-ray emission spectra of carbon nanotubes are similar to those of graphite. At resonant excitation, however, there are pronounced differences, suggesting that the σ-π hybridization is reflected in the spectra.

This thesis addresses the electronic structure of molecular and correlated solids using resonant inelastic soft X-ray scattering (RIXS), non-resonant X-ray emission, photoemissionand X-ray absorption spectroscopies. The use of monochromatised synchrotron radiation and improved energy resolution for X-ray emission have made it possible to elucidate the normal state transport properties and to get further insight into the electron-vibration coupling in fullerenes and the related compounds. The latter is particularly important in order to understand the physical mechanism of superconductivity in fullerene materials. The characteristic intermolecular charge transfer times in K3C60 are found to be longer than the X-ray scattering time-scale (a few femtoseconds). The slow intermolecular charge transport emphasizes that the reduced fullerene compounds can not be treated as simple metals, but rather as systems with strong electron correlation. The electron structure and the bonding character of the more covalent transition metal (V, Ti, Nb) fullerides have been addressed. Evidence indicating the existence of chemical bond between the metal atom(s) and C60 is presented, and the nature of the bond is discussed by comparing RIXS spectroscopic measurements and theoretical predictions. The (crystal) momentum conservation is discussed by comparing the spectroscopic data of a quasi-1D (carbon nanotubes) and quasi-2D (graphite) systems. Finally, the intra-atomic electron-electron correlation is discussed in the case of double core-hole state photo-excitation and de-excitation processes. RIXS including intermediate states with two core vacancies has been observed for the first time in the soft X-ray region.

The subject of this thesis is to formulate effective energy expressions (Hamiltonians) of proteins and protein related systems. By use of equilibrium statistical mechanics we calculate thermodynamical functions, whereupon we compare the results from theory with experimental data. Papers 1-7 and 10-12 concern this problem. In addition, Paper 8 (P8) and Paper 9 (P9) are attached. Both these papers were finalized during the Ph.D. study. However, they are not related to proteins. / Papers II, III, V, VII, VIII, XI and XII are reprinted with kind permission of Elsevier, sciencedirect.com Papers VI and IX are reprinted with kind permission of the American Physical Society.

Ion insertion into electrode materials can be used to store energy in battery applications. In this thesis, photoelectron spectroscopic and x-ray absorption spectroscopic methods have been used to study the change of the electronic structure of host materials during electrochemical ion insertion. Specifically, the properties of ion insertion into nanoporous TiO2 were studied. It is demonstrated that the insertion of Li ions results in a reduction of the Ti4+ sites in TiO2 to Ti3+ sites close to the inserted Li ion. The intensity of the Ti3+ is directly correlated to the number of inserted electrons. It is also shown that the two phases resulting from moderate insertion can be detected by studying the electronic structure of inserted Li ions and the behavior observed can be correlated with electrochemical measurements. Insertion of ions into tungsten oxides is a potential candidate for smart window and display applications. Ion insertion into these materials was, also studied with electron spectroscopic methods. The insertion of H+ reduces W6+ to W5+ and further insertion results in a reduction to W4+. Cyclic voltammerty shows two reduction peaks where the first peak implies reduction of W6+ to W5+ and the second peak can be associated with further reduction to W4+. During the first charge/discharge cycles of a battery based on graphite anodes a solid electrolyte interface layer is formed on the electrode surface. This layer consumes some of the charge carrying Li ions, hence decreases the capacity of the battery. A careful characterization of this layer has been performed to aid in the further development of this type of battery.

A number of nanostructured systems has been investigated by means of Photoemission and X-ray absorption spectroscopies and by Scanning tunneling microscopy with emphasis on the geometric and electronic structure and the excited-state charge transfer dynamics. These systems comprise aromatic molecules on semiconductor surfaces (titanium dioxide), metal clusters, and an alkali-C60 compound. Electronic and geometric structure are complementary to each other, and changes in the geometric structure are accompanied by changes in the electronic structure. Therefore, a detailed investigation of the latter makes it possible to draw conclusions on the former. In particular, this close relationship has been used to characterise the adsorbate geometry of the pyridine-carboxylic acid monomers on rutile TiO2(110), which is determined by the strong substrate bond as well as interadsorbate interactions. Similarly, it has been found that bi-isonicotinic acid adsorbs on a nanostructured anatase TiO2 film by forming strong bonds between both carboxylic groups and the substrate titanium atoms. For deposited metal clusters, the core binding energies are found to mirror the cluster size. Resonant core electron spectroscopies have been employed to elucidate the excited-state charge transfer dynamics with respect to the transfer of an excited electron from the bi-isonicotinic acid and isonicotinic acid adsorbates to a titanium dioxide semiconductor surface. An important aspect has been the development of new variations of the method in order to be able to unravel the spectra of these relatively complex systems. While a strong excitonic effect localises the excited electron on the adsorbate for the lowest excited state, excitation to the higher excited states leads to an ultrarapid charge transfer on a low- to sub-femtosecond timescale. In LiC60 the character of the alkali-C60 bond has been investigated. The balance between the different energy contributions points to an ionic bond with an important element of covalency.

The physical and chemical properties of matter are to a high degree determined by the electronic structure. One of the most powerful experimental techniques to study the electronic structure is electron spectroscopy. Conventionally most of the investigations on molecules, carried out using this technique, have dealt with static information such as binding energies and localization of the electron. This thesis focuses on the currently expanding field more concerned with dynamic effects such as lifetimes and dissociation times. In particular, resonantly excited molecules have been studied. As an example, we have used the "core hole clock" method to determine the dissociation times of core excited water and ammonia molecules. These experiments are possible using a synchrotron light source and the experiments are based on ultra-fast dissociation of resonantly excited states. A similar experiment on doubly core-excited nitrogen molecules have revealed no sign of ultra-fast dissociation as the resulting spectral features contain vibrational progressions and therefore result from molecular decay. Molecules that dissociate on an ultra-fast timescale, i.e. in the low femtosecond regime, are interesting for several reasons. For instance, decay occurring in core excited oxygen fragments can be used to demonstrate a localization of the core hole through the existence of a Doppler effect. Also, the nature of the molecular intermediate state leading to ultra-fast dissociation can be of interest. For the oxygen molecule there is a debate concerning the assignment of the large absorption structure near the O1s ionization energy. We are able to disclose which photon wavelengths lead to ultra-fast dissociation. Direct information on the time dependence of electronic structure and molecular dynamics during the ionization process can be obtained through the use of fast pulsed lasers in pump-probe experiments. For such studies we have used the terawatt laser at the Lund Laser Center providing pulses down to 110 fs long to observe the decay of two different states in valence excited acetylene.