| 1. |
- Johansson, A., et al.
(author)
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Synthesis and photophysics of one mononuclear Mn(III) and one dinuclear Mn(III,III) complex covalently linked to a ruthenium(II) tris(bipyridyl) complex
- 2003
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In: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 42, s. 7502-7511
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Journal article (peer-reviewed)abstract
- The preparation of donor (D)-photosensitizer (S) arrays, consisting of a manganese complex as D and a ruthenium tris(bipyridyl) complex as S has been pursued. Two new ruthenium complexes containing coordinating sites for one (2a) and two manganese ions (3a) were prepared in order to provide models for the donor side of photosystem II in green plants. The manganese coordinating site consists of bridging and terminal phenolate as well as terminal pyridyl ligands. The corresponding ruthenium-manganese complexes, a manganese monomer 2b and dimer 3b, were obtained. For the dimer 3b, our data suggest that intramolecular electron transfer from manganese to photogenerated ruthenium(III) is fast, k(ET) > 5 x 10(7) s(-1).
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| 2. |
- Abrahamsson, M. L. A., et al.
(author)
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Ruthenium-manganese complexes for artificial photosynthesis : Factors controlling intramolecular electron transfer and excited-state quenching reactions
- 2002
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In: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 41:6, s. 1534-1544
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Journal article (peer-reviewed)abstract
- Continuing our work toward a system mimicking the electron-transfer steps from manganese to P-680(+) in photosystem II (PS II), we report a series of ruthenium(II)-manganese(II) complexes that display intramolecular electron transfer from manganese(II) to photooxidized ruthenium(III). The electron-transfer rate constant (k(ET)) values span a large range, 1 X 10(5)-2 x 10(7) s(-1), and we have investigated different factors that are responsible for the variation. The reorganization energies determined experimentally (lambda = 1.5-2.0 eV) are larger than expected for solvent reorganization in complexes of similar size in polar solvents (typically lambda approximate to 1.0 eV). This result indicates that the inner reorganization energy is relatively large and, consequently, that at moderate driving force values manganese complexes are not fast donors. Both the type of manganese ligand and the link between the two metals are shown to be of great importance to the electron-transfer rate. In contrast, we show that the quenching of the excited state of the ruthenium(II) moiety by manganese(II) in this series of complexes mainly depends on the distance between the metals. However, by synthetically modifying the sensitizer so that the lowest metal-to-ligand charge transfer state was localized on the nonbridging ruthenium(II) ligands, we could reduce the quenching rate constant in one complex by a factor of 700 without changing the bridging ligand. Still, the manganese(II)-ruthenium (III) electrontransfer rate constant was not reduced. Consequently, the modification resulted in a complex with very favorable properties.
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| 3. |
- Kikas, A., et al.
(author)
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Resonant inelastic x-ray scattering at the F 1s photoabsorption edge in LiF : Interplay of excitonic and conduction states, and Stokes' doubling
- 2004
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In: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 70:8
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Journal article (peer-reviewed)abstract
- The excitation-decay processes at the F 1s photoabsorption edge in LiF crystal are studied using resonant inelastic x-ray scattering spectroscopy. The Raman-type linear dispersion and the narrowing of the x-ray fluorescence peak are observed at resonant excitation. A theoretical model based on the Kramers-Heisenberg formula describes well the main features in fluorescence spectra and allows one to separate the contributions of the exciton and the conduction states in the scattering spectra. At the same time, the role of the shape of the spectral distribution within the incident radiation is emphasized as being critically sensitive to the number, kind, and onset of the spectral features which finally appear in the scattering spectra at a particular incident photon energy, particularly in the subthreshold excitation region.
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| 4. |
- Weissenrieder, Jonas, et al.
(author)
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Experimental evidence for a partially dissociated water bilayer on Ru{0001}
- 2004
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In: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 93:19
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Journal article (peer-reviewed)abstract
- Core-level photoelectron spectra, in excellent agreement with ab initio calculations, confirm that the stable wetting layer of water on Ru{0001} contains O-H and H2O in roughly 3:5 proportion, for OHx coverages between 0.25 and 0.7 ML, and T<170 K. Proton disorder explains why the wetting structure looks to low energy electron diffraction (LEED) to be an ordered p(root3xroot3)R30degrees adlayer, even though approximate to3/8 of its molecules are dissociated. Complete dissociation to atomic oxygen starts near 190 K. Low photon flux in the synchrotron experiments ensured that the diagnosis of the nature of the wetting structure quantified by LEED is free of beam-induced damage.
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| 5. |
- Lenells, Jonatan, 1981-
(author)
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Traveling wave solutions of the Camassa-Holm and Korteweg-de Vries equations
- 2004
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In: Journal of Nonlinear Mathematical Physics. - : Springer Science and Business Media LLC. - 1402-9251 .- 1776-0852. ; 11:4, s. 508-520
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Journal article (peer-reviewed)abstract
- We show that the smooth traveling waves of the Camassa-Holm equation naturally correspond to traveling waves of the Korteweg-de Vries equation.
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| 6. |
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| 7. |
- Bäck, Torbjörn, et al.
(author)
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A TOF-PET system for educational purposes
- 2002
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In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 477, s. 82-82
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Journal article (peer-reviewed)abstract
- A TOF-PET system has been designed and constructed for educational purposes. The aim of this system is to demonstrate the possibilities of positron emission tomography in general and the time-of-flight method in particular to the students of various courses at the Royal Institute of Technology, Stockholm, Sweden. The set-up consists of 48 small BaF2 crystals coupled to fast photomultipliers placed in a ring geometry. The signals of the photomultipliers are fed into fast constant fraction discriminators (CFD). The outputs of these are directed to a specially designed logic VME unit. which combines the CFD signals of 6 neighbouring channels to one signal by adding a different delay to each channel. The logic circuitry produces a prompt pulse for each event that serves as the start pulse for the 8-channel fast TDC. The delayed pulses act as the stop pulses for the TDC. In a computer. the measured times are converted into information about which the photomultipliers fired with the difference in the time of flight. The set-up is described and the results are presented.
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| 8. |
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| 9. |
- Eriksson, Torny, et al.
(author)
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Heterogeneity of homologously expressed Hypocrea jecorina (Trichoderma reesei) Cel7B catalytic module
- 2004
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In: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 271:7, s. 1266-1276
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Journal article (peer-reviewed)abstract
- The catalytic module of Hypocrea jecorina (previously Trichoderma reesei) Cel7B was homologously expressed by transformation of strain QM9414. Post-translational modifications in purified Cel7B preparations were analysed by enzymatic digestions, high performance chromatography, mass spectrometry and site-directed mutagenesis. Of the five potential sites found in the wild-type enzyme, only Asn56 and Asn182 were found to be N-glycosylated. GlcNAc(2)Man(5) was identified as the predominant N-glycan, although lesser amounts of GlcNAc(2)Man(7) and glycans carrying a mannophosphodiester bond were also detected. Repartition of neutral and charged glycan structures over the two glycosylation sites mainly accounts for the observed microheterogeneity of the protein. However, partial deamidation of Asn259 and a partially occupied O-glycosylation site give rise to further complexity in enzyme preparations.
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| 10. |
- Feifel, R., et al.
(author)
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Role of stray light in the formation of high-resolution resonant photoelectron spectra : an experimental and theoretical study of N-2
- 2004
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In: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 134:1, s. 49-65
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Journal article (peer-reviewed)abstract
- We show that the undular stray light, diffusely scattered by the optical system of a synchrotron beamline, can play an important role in the formation of high-resolution resonant photoelectron (RPE) spectra. The influence of the stray light is mediated through the Stokes doubling effect, with the Lorentzian tail of the spectral function being replaced by a more complicated form. This effect is shown to appear in the high-resolution resonant photoelectron spectrum of the N-2 molecule in which the spectral shape of the non-Raman (NR) bands differs qualitatively for the A(2)Pi(u) and X(2)Sigma(g)(+) final states. A particularly large enhancement of the non-Raman Stokes line is observed for the A-state while the picture is inverted for the X-state where the non-Raman band is suppressed. It is shown that the resonant photoemission profile is affected by two qualitatively different detunings, the detuning of the monochromatized line relative to the photoabsorption line and the detuning of the undulator harmonic relative to the same reference line. The experimental data show that the relative intensity of the non-Raman line strongly depends on the tuning of the undulator harmonic with respect to the selected monochromator bandpass, leading to a strong decrease of the Stokes line intensity for certain undulator detunings. A clear red-shift asymmetry for the decrease in the Stokes line intensity is observed when the monochromator line is detuned towards negative photon frequencies, whereas the picture is reverted for the situation of a positively detuned monochromator line. The results show the necessity to control the stray light and to investigate both the Raman and non-Raman contributions to the spectral profiles in order to avoid misinterpretation and in order to make full use of the information available in resonant photoemission spectra of molecules.
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