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  • 1.
    Durbeej, Bo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Quantum Chemical Studies of Protein-Bound Chromophores, UV-Light Induced DNA Damages, and Lignin Formation2004Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Quantum chemical methods have been used to provide a better understanding of the photochemistry of astaxanthin and phytochromobilin; the photoenzymic repair of UV-light induced DNA damages; and the formation of lignin.

    The carotenoid astaxanthin (AXT) is responsible for the colouration of lobster shell. In solution, the electronic absorption spectra of AXT peak in the 470-490 nm region, corresponding to an orange-red colouration. Upon binding to the lobster-shell protein-complex α-crustacyanin, the absorption maximum is shifted to 632 nm, yielding a slate-blue colouration. Herein, the structural origin of this bathochromic shift is investigated on the basis of recent experimental work.

    The tetrapyrrole phytochromobilin (PΦB) underlies the photoactivation of the plant photoreceptor phytochrome. Upon absorption of 660-nm light, PΦB isomerizes from a C15-Z,syn configuration (in the inactive form of the protein) to C15-E,anti (in the active form). In this work, a reaction mechanism for this isomerization is proposed.

    DNA photolyases are enzymes that repair DNA damages resulting from far-UV-light induced [2+2] cycloaddition reactions involving pyrimidine nucleobases. The catalytic activity of these enzymes is initiated by near-UV and visible light, and is governed by electron transfer processes between a catalytic cofactor of the enzyme and the DNA lesions. Herein, an explanation for the experimental observation that the repair of cyclobutane pyrimidine dimers (CPD) – the major type of lesion – proceeds by electron transfer from the enzyme to the dimer is presented. Furthermore, the formation of CPD is studied.

    Lignin is formed by dehydrogenative polymerization of hydroxycinnamyl alcohols. A detailed understanding of the polymerization mechanism and the factors controlling the outcome of the polymerization is, however, largely missing. Quantum chemical calculations on the initial dimerization step have been performed in order to gain some insight into these issues.

    Delarbeten
    1. On the bathochromic shift of the absorption by astaxanthin in crustacyanin: a quantum chemical study
    Öppna denna publikation i ny flik eller fönster >>On the bathochromic shift of the absorption by astaxanthin in crustacyanin: a quantum chemical study
    2003 Ingår i: Chemical Physics Letters, ISSN 0009-2614, Vol. 375, nr 1-2, s. 30-38Artikel i tidskrift (Refereegranskat) Published
    Identifikatorer
    urn:nbn:se:uu:diva-92091 (URN)
    Tillgänglig från: 2004-09-03 Skapad: 2004-09-03Bibliografiskt granskad
    2. Conformational dependence of the electronic absorption by astaxanthin and its implications for the bathochromic shift in crustacyanin
    Öppna denna publikation i ny flik eller fönster >>Conformational dependence of the electronic absorption by astaxanthin and its implications for the bathochromic shift in crustacyanin
    2004 Ingår i: Physical Chemistry Chemical Physics, ISSN 1463-9076, Vol. 6, s. 4190-4198Artikel i tidskrift (Refereegranskat) Published
    Identifikatorer
    urn:nbn:se:uu:diva-92092 (URN)
    Tillgänglig från: 2004-09-03 Skapad: 2004-09-03Bibliografiskt granskad
    3. Phytochromobilin C15-Z,syn to C15-E,anti isomerization - concerted or stepwise?
    Öppna denna publikation i ny flik eller fönster >>Phytochromobilin C15-Z,syn to C15-E,anti isomerization - concerted or stepwise?
    Artikel i tidskrift (Refereegranskat) Submitted
    Identifikatorer
    urn:nbn:se:uu:diva-92093 (URN)
    Tillgänglig från: 2004-09-03 Skapad: 2004-09-03Bibliografiskt granskad
    4. Thermodynamics of the photoenzymic repair mechanism studied by density functional theory
    Öppna denna publikation i ny flik eller fönster >>Thermodynamics of the photoenzymic repair mechanism studied by density functional theory
    2000 Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, Vol. 122, nr 41, s. 10126-10132Artikel i tidskrift (Refereegranskat) Published
    Identifikatorer
    urn:nbn:se:uu:diva-92094 (URN)
    Tillgänglig från: 2004-09-03 Skapad: 2004-09-03Bibliografiskt granskad
    5. On the formation of cyclobutane pyrimidine dimers in UV-irradiated DNA: why are thymines more reactive?
    Öppna denna publikation i ny flik eller fönster >>On the formation of cyclobutane pyrimidine dimers in UV-irradiated DNA: why are thymines more reactive?
    2003 Ingår i: Photochemistry and Photobiology, ISSN 0031-8655, Vol. 78, nr 2, s. 159-167Artikel i tidskrift (Refereegranskat) Published
    Identifikatorer
    urn:nbn:se:uu:diva-92095 (URN)
    Tillgänglig från: 2004-09-03 Skapad: 2004-09-03Bibliografiskt granskad
    6. Electron-transfer induced repair of 6-4 photoproducts in DNA: A computational study
    Öppna denna publikation i ny flik eller fönster >>Electron-transfer induced repair of 6-4 photoproducts in DNA: A computational study
    2007 (Engelska)Ingår i: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 111, nr 12, s. 2351-2361Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The mechanism employed by DNA photolyase to repair 6-4 photoproducts in UV-damaged DNA is explored by means of quantum chemical calculations. Considering the repair of both oxetane and azetidine lesions, it is demonstrated that reduction as well as oxidation enables a reversion reaction by creating anionic or cationic radicals that readily fragment into monomeric pyrimidines. However, on the basis of calculated reaction energies indicating that electron transfer from the enzyme to the lesion is a much more favorable process than electron transfer in the opposite direction, it is suggested that the photoenzymic repair can only occur by way of an anionic mechanism. Furthermore, it is shown that reduction of the oxetane facilitates a mechanism involving cleavage of the C−O bond followed by cleavage of the C−C bond, whereas reductive fragmentation of the azetidine may proceed with either of the intermonomeric C−N and C−C bonds cleaved as the first step. From calculations on neutral azetidine radicals, a significant increase in the free-energy barrier for the initial fragmentation step upon protonation of the carbonylic oxygens is predicted. This effect can be attributed to protonation serving to stabilize reactant complexes more than transition structures.

    Nationell ämneskategori
    Kemi
    Identifikatorer
    urn:nbn:se:uu:diva-92096 (URN)10.1021/jp0676383 (DOI)000245083600013 ()17388321 (PubMedID)
    Tillgänglig från: 2004-09-03 Skapad: 2004-09-03 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
    7. A density functional theory study of coniferyl alcohol intermonomeric linkages in lignin - three-dimensional structures, stabilities and the thermodynamic control hypothesis
    Öppna denna publikation i ny flik eller fönster >>A density functional theory study of coniferyl alcohol intermonomeric linkages in lignin - three-dimensional structures, stabilities and the thermodynamic control hypothesis
    2003 Ingår i: Holzforschung, ISSN 0018-3830, Vol. 57, nr 2, s. 150-164Artikel i tidskrift (Refereegranskat) Published
    Identifikatorer
    urn:nbn:se:uu:diva-92097 (URN)
    Tillgänglig från: 2004-09-03 Skapad: 2004-09-03Bibliografiskt granskad
    8. Spin distribution in dehydrogenated coniferyl alcohol and associated dilignol radicals
    Öppna denna publikation i ny flik eller fönster >>Spin distribution in dehydrogenated coniferyl alcohol and associated dilignol radicals
    2003 Ingår i: Holzforschung, ISSN 0018-3830, Vol. 57, nr 1, s. 59-61Artikel i tidskrift (Refereegranskat) Published
    Identifikatorer
    urn:nbn:se:uu:diva-92098 (URN)
    Tillgänglig från: 2004-09-03 Skapad: 2004-09-03Bibliografiskt granskad
    9. Formation of β-O-4 lignin models - a theoretical study
    Öppna denna publikation i ny flik eller fönster >>Formation of β-O-4 lignin models - a theoretical study
    2003 Ingår i: Holzforschung, ISSN 0018-3830, Vol. 57, nr 5, s. 466-478Artikel i tidskrift (Refereegranskat) Published
    Identifikatorer
    urn:nbn:se:uu:diva-92099 (URN)
    Tillgänglig från: 2004-09-03 Skapad: 2004-09-03Bibliografiskt granskad
  • 2.
    Durbeej, Bo
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Borg, Anders
    Eriksson, Leif
    Phytochromobilin C15-Z,syn to C15-E,anti isomerization - concerted or stepwise?Artikel i tidskrift (Refereegranskat)
  • 3.
    Durbeej, Bo
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Eriksson, Leif
    A density functional theory study of coniferyl alcohol intermonomeric linkages in lignin - three-dimensional structures, stabilities and the thermodynamic control hypothesis2003Ingår i: Holzforschung, ISSN 0018-3830, Vol. 57, nr 2, s. 150-164Artikel i tidskrift (Refereegranskat)
  • 4.
    Durbeej, Bo
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Eriksson, Leif
    Conformational dependence of the electronic absorption by astaxanthin and its implications for the bathochromic shift in crustacyanin2004Ingår i: Physical Chemistry Chemical Physics, ISSN 1463-9076, Vol. 6, s. 4190-4198Artikel i tidskrift (Refereegranskat)
  • 5.
    Durbeej, Bo
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Eriksson, Leif
    Formation of β-O-4 lignin models - a theoretical study2003Ingår i: Holzforschung, ISSN 0018-3830, Vol. 57, nr 5, s. 466-478Artikel i tidskrift (Refereegranskat)
  • 6.
    Durbeej, Bo
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Eriksson, Leif
    On the bathochromic shift of the absorption by astaxanthin in crustacyanin: a quantum chemical study2003Ingår i: Chemical Physics Letters, ISSN 0009-2614, Vol. 375, nr 1-2, s. 30-38Artikel i tidskrift (Refereegranskat)
  • 7.
    Durbeej, Bo
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Eriksson, Leif
    On the formation of cyclobutane pyrimidine dimers in UV-irradiated DNA: why are thymines more reactive?2003Ingår i: Photochemistry and Photobiology, ISSN 0031-8655, Vol. 78, nr 2, s. 159-167Artikel i tidskrift (Refereegranskat)
  • 8.
    Durbeej, Bo
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Eriksson, Leif
    Spin distribution in dehydrogenated coniferyl alcohol and associated dilignol radicals2003Ingår i: Holzforschung, ISSN 0018-3830, Vol. 57, nr 1, s. 59-61Artikel i tidskrift (Refereegranskat)
  • 9.
    Durbeej, Bo
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Eriksson, Leif
    Thermodynamics of the photoenzymic repair mechanism studied by density functional theory2000Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, Vol. 122, nr 41, s. 10126-10132Artikel i tidskrift (Refereegranskat)
  • 10.
    Ericsson, Marie
    et al.
    Centre for Quantum Computation, DAMTP, University of Cambridge, UK.
    Kult, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Sjöqvist, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Åberg, Johan
    Centre for Quantum Computation, DAMTP, Cambridge, UK.
    Nodal free geometric phases: concept and application to geometric quantum computation2008Ingår i: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 372, nr 5, s. 596-599Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nodal free geometric phases are the eigenvalues of the final member of a parallel transporting family of unitary operators. These phases are gauge invariant, always well defined, and can be measured interferometrically. Nodal free geometric phases can be used to construct various types of quantum phase gates.

  • 11.
    Ericsson, Marie
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Sjöqvist, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Dlaczego kot Schrödingera laduje na czterech lapach2001Ingår i: Delta, ISSN 0137-3005, nr 11, s. 1-Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 12.
    Ericsson, Marie
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Sjöqvist, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Quantum computation using the Aharonov-Casher set up2002Ingår i: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 303, nr 1, s. 7-10Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is argued that the Aharonov-Casher set up could be used as the basic building block for quantum computation. We demonstrate explicitly in this scenario one- and two-qubit phase shift gates that are fault tolerant to deformations of the path when encircling two sites of the computational system around each other.

  • 13.
    Ericsson, Marie
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Sjöqvist, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Towards a quantum Hall effect for atoms using electric fields2002Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 65, nr 1, s. 013607-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An atomic analogue of Landau quantization based on the Aharonov-Casher (AC) interaction is developed. The effect provides a first step towards an atomic quantum Hall system using electric fields, which may be realized in a Bose-Einstein condensate.

  • 14.
    Ericsson, Marie
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Kvantkemi.
    Sjöqvist, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Kvantkemi.
    Goscinski, Osvaldo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Kvantkemi.
    Degree of electron-nuclear entanglement in the E x e Jahn-Teller system1999Ingår i: Proceedings of the XIV International Symposium on Electron-Phonon Dynamics and Jahn-Teller Effect: Erice, Italy, 7-13 July 1998 / [ed] G. Bevilacqua, L. Martinelli, N. Terzi, Singapore: World Scientific Publishing , 1999, s. 20-Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Jahn-Teller systems exhibit strong coupling between the electronic and nuclear degrees of freedom. We analyse how linear and quadratic coupling affect the electron-nuclear entanglement in the $E\otimes \epsilon$ system. A measure of quantum entanglement, recently developed by Shimony [Ann. New York Acad. Sci. 755, 675 (1995)], is used. States in the adiabatic regime with quadratic coupling are analysed. The electron-nuclear entanglement in vibronic states of the linear Exe model is calculated numerically. The physical significance of electron-nuclear entanglement is discussed in terms of reduction factors and magnetic vibrational circular dichroism.

  • 15.
    Holmgren, Sverker
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    Peterson, Christer
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    Karlsson, Hans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Time-marching methods for the time-dependent Schrödinger equation2004Ingår i: Proc. Int. Conference on Computational and Mathematical Methods in Science and Engineering: CMMSE-2004, Uppsala, Sweden: Uppsala University , 2004, s. 53-56Konferensbidrag (Övrigt vetenskapligt)
  • 16.
    Hällstig, Emil
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Nematic Liquid Crystal Spatial Light Modulators for Laser Beam Steering2004Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Laser beam control is important in many applications. Phase modulating spatial light modulators (SLMs) can be used to electronically alter the phase distribution of an optical wave-front and thus change the direction and shape of a laser beam. Physical constraints set limitations to the SLM and an ideal phase distribution can usually not be realised. In order to understand how such components can be used for non-mechanical beam control three nematic liquid crystal (NLC) SLMs have been thoroughly characterised and modelled.

    The pixel structure and phase quantisation give a discrepancy between ideal and realised phase distributions. The impact on beam steering capability was examined by measurements and simulations of the intensity distribution in the far-field.

    In two of the studied SLMs the pixel period was shorter than the thickness of the LC layer giving the optical phase shift. This results in a so-called “fringing field”, which was shown to degrade the phase modulation and couple light between polarisation modes. The deformation of the LC was simulated and a finite-difference time-domain (FDTD) algorithm was used to calculate how polarised light propagates through the optically anisotropic SLM.

    Non-mechanical beam steering and tracking in an optical free-space communication link were demonstrated. Continual optimisation of the steering angle was achieved by feedback from a video camera.

    The optical properties of the SLM in the time period right after a voltage update were studied. It was shown how light is redistributed between orders during the switching from one blazed grating to another. By appropriate choice of the blazed gratings the effects on the diffraction efficiency can be minimised.

    The detailed knowledge of the SLM structure and its response to electronic control makes it possible to predict and optimise the device performance in future systems.

    Delarbeten
    1. Intensity variations using a quantized spatial light modulator for non-mechanical beam steering
    Öppna denna publikation i ny flik eller fönster >>Intensity variations using a quantized spatial light modulator for non-mechanical beam steering
    2003 Ingår i: Optical Engineering, ISSN 0091-3286, Vol. 42, nr 3, s. 613-619Artikel i tidskrift (Refereegranskat) Published
    Identifikatorer
    urn:nbn:se:uu:diva-92439 (URN)
    Tillgänglig från: 2004-11-24 Skapad: 2004-11-24Bibliografiskt granskad
    2. Fringing fields in a nematic liquid crystal spatial light modulator for beam steering
    Öppna denna publikation i ny flik eller fönster >>Fringing fields in a nematic liquid crystal spatial light modulator for beam steering
    Visa övriga...
    2004 Ingår i: Journal of Modern Optics, ISSN 00950-0340, Vol. 51, nr 8, s. 613-619Artikel i tidskrift (Refereegranskat) Published
    Identifikatorer
    urn:nbn:se:uu:diva-92440 (URN)
    Tillgänglig från: 2004-11-24 Skapad: 2004-11-24Bibliografiskt granskad
    3. Polarization properties of a nematic liquid-crystal spatial light modulator for phase modulation
    Öppna denna publikation i ny flik eller fönster >>Polarization properties of a nematic liquid-crystal spatial light modulator for phase modulation
    2005 (Engelska)Ingår i: Optical Society of America. Journal A: Optics, Image Science, and Vision, ISSN 1084-7529, E-ISSN 1520-8532, Vol. 22, nr 1, s. 177-184Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The polarization properties of a nematic zero-twist liquid-crystal (NLC) spatial light modulator (SLM) were studied. A large ratio between the liquid-crystal (LC) layer thickness and the pixel pitch combined with spatial variations in the applied electric field causes fringing fields between pixels. Depending on the LC alignment, the electric field components within the LC layer can result in a twist deformation. The produced inhomogeneous optical anisotropy affects the polarization of light propagating through the device. We experimentally examined polarization effects in different diffraction orders for both binary and blazed phase gratings. Simulations of the LC deformation together with finite-difference time-domain simulations for the optical propagation were used to calculate the corresponding far-field intensities. It was demonstrated how rigorous simulations of the NLC SLM properties can be used to understand the polarization features of different diffraction orders.

    Nationell ämneskategori
    Naturvetenskap
    Identifikatorer
    urn:nbn:se:uu:diva-92441 (URN)10.1364/JOSAA.22.000177 (DOI)15669628 (PubMedID)
    Tillgänglig från: 2004-11-24 Skapad: 2004-11-24 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
    4. Retrocommunication utilizing electroabsorption modulators and non-mechanical beam steering
    Öppna denna publikation i ny flik eller fönster >>Retrocommunication utilizing electroabsorption modulators and non-mechanical beam steering
    Visa övriga...
    2005 (Engelska)Ingår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 44, nr 4, s. 045001-Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    A novel retrocommunication link utilizing reflective multiplequantum well (MQW) optical modulators and nonmechanical beamsteering and tracking is demonstrated. Large aperture reflective MQWmodulators using AlGaAs/GaAs are optimized and manufactured. Themodulators exhibit a contrast ratio larger than 4:1 and a modulationbandwidth of 10 MHz. Nonmechanical beam steering and tracking arestudied using nematic liquid crystal (NLC) spatial light modulators(SLMs). The communication link is comprised of a retromodulating arraywith four MQW modulators and a transceiver using a NLC SLM for beamsteering and tracking. Transfer of audio, real-time image data and pseudorandombit sequences over 100-m range while tracking the movingretromodulator is shown. The link is capable of transferring data at approximately8 Mbps.

    Nationell ämneskategori
    Naturvetenskap
    Identifikatorer
    urn:nbn:se:uu:diva-92442 (URN)10.1117/1.1883063 (DOI)
    Tillgänglig från: 2004-11-24 Skapad: 2004-11-24 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
    5. Temporal properties of a nematic liquid-crystal spatial light modulator used for laser beam steering and tracking
    Öppna denna publikation i ny flik eller fönster >>Temporal properties of a nematic liquid-crystal spatial light modulator used for laser beam steering and tracking
    Ingår i: Applied Optics, ISSN 0003-6935Artikel i tidskrift (Refereegranskat) Submitted
    Identifikatorer
    urn:nbn:se:uu:diva-92443 (URN)
    Tillgänglig från: 2004-11-24 Skapad: 2004-11-24Bibliografiskt granskad
  • 17.
    Hällstig, Emil
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Kvantkemi.
    Martin, Torleif
    Sjöqvist, Lars
    Lindgren, Mikael
    Polarization properties of a nematic liquid-crystal spatial light modulator for phase modulation2005Ingår i: Optical Society of America. Journal A: Optics, Image Science, and Vision, ISSN 1084-7529, E-ISSN 1520-8532, Vol. 22, nr 1, s. 177-184Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The polarization properties of a nematic zero-twist liquid-crystal (NLC) spatial light modulator (SLM) were studied. A large ratio between the liquid-crystal (LC) layer thickness and the pixel pitch combined with spatial variations in the applied electric field causes fringing fields between pixels. Depending on the LC alignment, the electric field components within the LC layer can result in a twist deformation. The produced inhomogeneous optical anisotropy affects the polarization of light propagating through the device. We experimentally examined polarization effects in different diffraction orders for both binary and blazed phase gratings. Simulations of the LC deformation together with finite-difference time-domain simulations for the optical propagation were used to calculate the corresponding far-field intensities. It was demonstrated how rigorous simulations of the NLC SLM properties can be used to understand the polarization features of different diffraction orders.

  • 18.
    Hällstig, Emil
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Sjöqvist, Lars
    Lindgren, Mikael
    Intensity variations using a quantized spatial light modulator for non-mechanical beam steering2003Ingår i: Optical Engineering, ISSN 0091-3286, Vol. 42, nr 3, s. 613-619Artikel i tidskrift (Refereegranskat)
  • 19.
    Hällstig, Emil
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Sjöqvist, Lars
    Lindgren, Mikael
    Temporal properties of a nematic liquid-crystal spatial light modulator used for laser beam steering and trackingIngår i: Applied Optics, ISSN 0003-6935Artikel i tidskrift (Refereegranskat)
  • 20.
    Hällstig, Emil
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Stigwall, Johan
    Martin, Torleif
    Sjöqvist, Lars
    Lindgren, Mikael
    Fringing fields in a nematic liquid crystal spatial light modulator for beam steering2004Ingår i: Journal of Modern Optics, ISSN 00950-0340, Vol. 51, nr 8, s. 613-619Artikel i tidskrift (Refereegranskat)
  • 21.
    Hällstig, Emil
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Kvantkemi.
    Öhgren, Johan
    Allard, Lars
    Sjöqvist, Lars
    Engström, David
    Hård, Sverker
    Ågren, Daniel
    Junique, Stephane
    Wang, Qin
    Noharet, Bertrand
    Retrocommunication utilizing electroabsorption modulators and non-mechanical beam steering2005Ingår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 44, nr 4, s. 045001-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel retrocommunication link utilizing reflective multiplequantum well (MQW) optical modulators and nonmechanical beamsteering and tracking is demonstrated. Large aperture reflective MQWmodulators using AlGaAs/GaAs are optimized and manufactured. Themodulators exhibit a contrast ratio larger than 4:1 and a modulationbandwidth of 10 MHz. Nonmechanical beam steering and tracking arestudied using nematic liquid crystal (NLC) spatial light modulators(SLMs). The communication link is comprised of a retromodulating arraywith four MQW modulators and a transceiver using a NLC SLM for beamsteering and tracking. Transfer of audio, real-time image data and pseudorandombit sequences over 100-m range while tracking the movingretromodulator is shown. The link is capable of transferring data at approximately8 Mbps.

  • 22.
    Itsenko, Oleksiy
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Norberg, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Rasmussen, Torben
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Långström, Bengt
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Chatgilialoglu, Chryssostomos
    Radical Carbonylation with [11C]Carbon Monoxide Promoted by Oxygen-Centered Radicals: Experimental and DFT studies of the mechanism2007Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 129, nr 29, s. 9020-9031Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Photoinitiated carbonylation of alkyl iodides with [11C]carbon monoxide (11C t1/2 = 20.4 min) is enhanced by ketones that have lowest-lying excited triplet state of nπ* character. For example, adding 5 mol % of acetophenone increases radiochemical yields from 3 to 59% in brief 6-min long reactions. Similar or higher yields were achieved by adding di-tert-butyl peroxide. Since radicaloid nπ* exited-state ketones and tert-butoxyl radicals have similar reactivity, the photosensitization proceeds most likely via a H-atom transfer mechanism rather than via energy transfer. We propose a mechanism that can account for the enhancement as well as for the formation of observed byproducts. The energy profile obtained by DFT calculations support the feasibility of the mechanism, and observed experimental differences in reactivity could be well rationalized by the calculated data. NBO calculations were performed to further analyze the obtained energetics. Various [carbonyl-11C]esters and some [carbonyl-11C]amides were synthesized in good radiochemical yields from primary and secondary alkyl iodides illustrating the utility of dialkyl peroxides to accelerate the carbonylations. These findings have potential in elaborating new synthetic protocols for the production of 11C-labeled tracers for positron emission tomography.

  • 23. Komaguchi, Kenji
    et al.
    Norberg, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Nakazawa, Naoko
    Shiotani, Masaru
    Persson, Petter
    Lunell, Sten
    Direct ESR evidence for SH2 type reaction of methyl radical with methylsilane and methylgermane in a low temperature solid: A deuterium labeling study2005Ingår i: Chemical Physics Letters, ISSN 0009-2614, Vol. 410, s. 1-5Artikel i tidskrift (Refereegranskat)
  • 24.
    Kult, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Quantum Holonomies: Concepts and Applications to Quantum Computing and Interferometry2007Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Quantum holonomies are investigated in different contexts.

    A geometric phase is proposed for decomposition dependent evolution, where each component of a given decomposition of a mixed state evolves independently. It is shown that this geometric phase only depends on the path traversed in the space of decompositions.

    A holonomy is associated to general paths of subspaces of a Hilbert space, both discrete and continuous. This opens up the possibility of constructing quantum holonomic gates in the open path setting. In the discrete case it is shown that it is possible to associate two distinct holonomies to a given path. Interferometric setups for measuring both holonomies are

    provided. It is further shown that there are cases when the holonomy is only partially defined. This has no counterpart in the Abelian setting.

    An operational interpretation of amplitudes of density operators is provided. This allows for a direct interferometric realization of Uhlmann's parallelity condition, and the possibility of measuring the Uhlmann holonomy for sequences of density operators.

    Off-diagonal geometric phases are generalized to the non-Abelian case. These off-diagonal holonomies are undefined for cyclic evolution, but must contain members of non-zero rank if all standard holonomies are undefined. Experimental setups for measuring the off-diagonal holonomies are proposed.

    The concept of nodal free geometric phases is introduced. These are constructed from gauge invariant quantities, but do not share the nodal point structure of geometric phases and off-diagonal geometric phases. An interferometric setup for measuring nodal free geometric phases is provided, and it is shown that these phases could be useful in geometric quantum computation.

    A holonomy associated to a sequence of quantum maps is introduced. It is shown that this holonomy is related to the Uhlmann holonomy. Explicit examples are provided to illustrate the general idea.

    Delarbeten
    1. Geometry of decomposition dependent evolutions of mixed states
    Öppna denna publikation i ny flik eller fönster >>Geometry of decomposition dependent evolutions of mixed states
    2004 (Engelska)Ingår i: International Journal of Quantum Information, ISSN 0219-7499, Vol. 2, nr 2, s. 247-256Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    We examine evolutions where each component of a given decomposition of a mixed quantal state evolves independently in a unitary fashion. The geometric phase and parallel transport conditions for this type of decomposition dependent evolution are delineated. We compare this geometric phase with those previously defined for unitarily evolving mixed states, and mixed state evolutions governed by completely positive maps.

    Nyckelord
    Geometric phase, mixed quantum states, conditional quantum dynamics
    Nationell ämneskategori
    Fysik
    Forskningsämne
    Fysik
    Identifikatorer
    urn:nbn:se:uu:diva-96146 (URN)10.1142/S0219749904000250 (DOI)000227719600008 ()
    Tillgänglig från: 2007-09-03 Skapad: 2007-09-03 Senast uppdaterad: 2011-10-06
    2. Noncyclic geometric changes of quantum states
    Öppna denna publikation i ny flik eller fönster >>Noncyclic geometric changes of quantum states
    2006 (Engelska)Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 74, nr 2, s. 022106-Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Non-Abelian quantum holonomies, i.e., unitary state changes solely induced by geometric properties of a quantum system, have been much under focus in the physics community as generalizations of the Abelian Berry phase. Apart from being a general phenomenon displayed in various subfields of quantum physics, the use of holonomies has lately been suggested as a robust technique to obtain quantum gates; the building blocks of quantum computers. Non-Abelian holonomies are usually associated with cyclic changes of quantum systems, but here we consider a generalization to noncyclic evolutions. We argue that this open-path holonomy can be used to construct quantum gates. We also show that a structure of partially defined holonomies emerges from the open-path holonomy. This structure has no counterpart in the Abelian setting. We illustrate the general ideas using an example that may be accessible to tests in various physical systems.

    Nyckelord
    Non-Abelian geometric phase, quantum holonomy, quantum computation
    Nationell ämneskategori
    Fysik
    Forskningsämne
    Fysik
    Identifikatorer
    urn:nbn:se:uu:diva-96147 (URN)10.1103/PhysRevA.74.022106 (DOI)000240238300017 ()
    Tillgänglig från: 2007-09-03 Skapad: 2007-09-03 Senast uppdaterad: 2017-12-14
    3. Manifestations of quantum holonomy in interferometry
    Öppna denna publikation i ny flik eller fönster >>Manifestations of quantum holonomy in interferometry
    2006 (Engelska)Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 74, nr 6, s. 062101-Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Abelian and non-Abelian geometric phases, known as quantum holonomies, have attracted considerable attention in the past. Here, we show that it is possible to associate nonequivalent holonomies to discrete sequences of subspaces in a Hilbert space. We consider two such holonomies that arise naturally in interferometer settings. For sequences approximating smooth paths in the base (Grassmann) manifold, these holonomies both approach the standard holonomy. In the one-dimensional case the two types of holonomies are Abelian and coincide with Pancharatnam's geometric phase factor. The theory is illustrated with a model example of projective measurements involving angular momentum coherent states.

    Nyckelord
    Quantum holonomy, geometric phase, quantum interferometry, spin-coherent states
    Nationell ämneskategori
    Fysik
    Forskningsämne
    Fysik
    Identifikatorer
    urn:nbn:se:uu:diva-96148 (URN)10.1103/PhysRevA.74.062101 (DOI)000243166700014 ()
    Tillgänglig från: 2007-09-03 Skapad: 2007-09-03 Senast uppdaterad: 2017-12-14
    4. Operational approach to the Uhlmann holonomy
    Öppna denna publikation i ny flik eller fönster >>Operational approach to the Uhlmann holonomy
    2007 (Engelska)Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 75, nr 3, s. 032106-Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    We suggest a physical interpretation of the Uhlmann amplitude of a density operator. Given this interpretation we propose an operational approach to obtain the Uhlmann condition for parallelity. This allows us to realize parallel transport along a sequence of density operators by an iterative preparation procedure. At the final step the resulting Uhlmann holonomy can be determined via interferometric measurements.

    Nyckelord
    Quantum holonomy, density operators, quantum interferometry
    Nationell ämneskategori
    Fysik
    Forskningsämne
    Fysik
    Identifikatorer
    urn:nbn:se:uu:diva-96149 (URN)10.1103/PhysRevA.75.032106 (DOI)000245326300023 ()
    Anmärkning
    Also in Virtual Journal of Quantum Information, March issue 2007.Tillgänglig från: 2007-09-03 Skapad: 2007-09-03 Senast uppdaterad: 2017-12-14
    5. Non-Abelian generalization of off-diagonal geometric phases
    Öppna denna publikation i ny flik eller fönster >>Non-Abelian generalization of off-diagonal geometric phases
    2007 (Engelska)Ingår i: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 78, nr 6, s. 60004-Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    If a quantum system evolves in a noncyclic fashion the corresponding geometric phase or holonomy may not be fully defined. Off-diagonal geometric phases have been developed to deal with such cases. Here, we generalize these phases to the non-Abelian case, by introducing off-diagonal holonomies that involve evolution of more than one subspace of the underlying Hilbert space. Physical realizations of the off-diagonal holonomies in adiabatic evolution and interferometry are put forward.

    Nationell ämneskategori
    Fysik
    Forskningsämne
    Fysik
    Identifikatorer
    urn:nbn:se:uu:diva-96150 (URN)10.1209/0295-5075/78/60004 (DOI)000248593700004 ()
    Tillgänglig från: 2007-09-03 Skapad: 2007-09-03 Senast uppdaterad: 2017-12-14
    6. Nodal free geometric phases: concept and application to geometric quantum computation
    Öppna denna publikation i ny flik eller fönster >>Nodal free geometric phases: concept and application to geometric quantum computation
    2008 (Engelska)Ingår i: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 372, nr 5, s. 596-599Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Nodal free geometric phases are the eigenvalues of the final member of a parallel transporting family of unitary operators. These phases are gauge invariant, always well defined, and can be measured interferometrically. Nodal free geometric phases can be used to construct various types of quantum phase gates.

    Nyckelord
    Geometric phase, quantum gates, quantum interferometry
    Nationell ämneskategori
    Fysik
    Forskningsämne
    Fysik
    Identifikatorer
    urn:nbn:se:uu:diva-96151 (URN)10.1016/j.physleta.2007.08.022 (DOI)000252835300011 ()
    Tillgänglig från: 2007-09-03 Skapad: 2007-09-03 Senast uppdaterad: 2017-12-14
    7. Holonomy for quantum channels
    Öppna denna publikation i ny flik eller fönster >>Holonomy for quantum channels
    2008 (Engelska)Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 77, nr 1, s. 012114-Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    A quantum holonomy reflects the curvature of some underlying structure of quantum-mechanical systems, such as that associated with quantum states. Here, we extend the notion of holonomy to families of quantum channels, i.e., trace-preserving completely positive maps. By the use of the Jamiolkowski isomorphism, we show that the proposed channel holonomy is related to the Uhlmann holonomy. The general theory is illustrated for specific examples. We put forward a physical realization of the channel holonomy in terms of interferometry. This enables us to identify a gauge-invariant physical object that directly relates to the channel holonomy. Parallel transport condition and concomitant gauge structure are delineated in the case of smoothly parametrized families of channels. Finally, we point out that interferometer tests that have been carried out in the past to confirm the 4 pi rotation symmetry of the neutron spin can be viewed as early experimental realizations of the channel holonomy.

    Nyckelord
    Geometric phase, quantum holonomy, completely positive maps, quantum channels, Uhlmann holonomy, mixed quantum states, quantum interferometry, Jamiolkowski isomorphism
    Nationell ämneskategori
    Fysik
    Forskningsämne
    Fysik
    Identifikatorer
    urn:nbn:se:uu:diva-96152 (URN)10.1103/PhysRevA.77.012114 (DOI)000252862000029 ()
    Tillgänglig från: 2007-09-03 Skapad: 2007-09-03 Senast uppdaterad: 2017-12-14
  • 25.
    Kult, David
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Åberg, Johan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Sjöqvist, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Noncyclic geometric changes of quantum states2006Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 74, nr 2, s. 022106-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Non-Abelian quantum holonomies, i.e., unitary state changes solely induced by geometric properties of a quantum system, have been much under focus in the physics community as generalizations of the Abelian Berry phase. Apart from being a general phenomenon displayed in various subfields of quantum physics, the use of holonomies has lately been suggested as a robust technique to obtain quantum gates; the building blocks of quantum computers. Non-Abelian holonomies are usually associated with cyclic changes of quantum systems, but here we consider a generalization to noncyclic evolutions. We argue that this open-path holonomy can be used to construct quantum gates. We also show that a structure of partially defined holonomies emerges from the open-path holonomy. This structure has no counterpart in the Abelian setting. We illustrate the general ideas using an example that may be accessible to tests in various physical systems.

  • 26.
    Larson, Jonas
    et al.
    NORDITA, Stockholm, Sweden.
    Sjöqvist, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Jahn-Teller-induced Berry phase in spin-orbit-coupled Bose-Einstein condensates2009Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 79, s. 043627-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate that Berry phases may greatly affect the dynamics of spin-orbit coupled Bose-Einstein condensates. The effective model Hamiltonian under consideration is shown to be equivalent to the Exe Jahn-Teller model first introduced in molecular physics. The corresponding conical intersection is identified and the Berry phase acquired for a wave packet encircling the intersection is studied. It is found that this phase manifests itself in the density profile of the condensate, making it a directly measurable quantity via time-of-flight detection. Moreover, the non-Abelian gauge structure of the system is addressed and we verify how it affects the dynamics.

  • 27.
    Llano, Jorge
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Kvantkemi.
    Eriksson, Leif A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi.
    First Principles Electrochemical Study of Redox Events in DNA Bases and Chemical Repair in Aqueous Solution2004Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 6, s. 2426-2433Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Primary and secondary radiation-induced damage to DNA, and chemical repair of the lesions on the nucleobases in solution involve a cascade of proton transfer (PT), electron transfer (ET), and proton-coupled electron transfer (PT-ET) reactions. The rate constants of these reactions depend on the standard Gibbs energy changes that can be derived from experiment. We here apply a first principles approach to calculate standard Gibbs energy changes of proton, electron, and proton-coupled electron transfer reactions in solution, wherein electrons and protons participate as independent ions; data that is fully compatible with that experimentally derived. Hence, the thermodynamic feasibility of ET and PT-ET pathways for these reactions depending on the effective concentration of hydrogen ions can be directly rationalized from first principles. The focus of this study is the primary and secondary ionization events in nucleobases in the presence of hydrogen atoms, solvated electrons and protons in aqueous solution, leading to the formation of nucleobase radical anions B˙, radical cations B˙+ and their major deprotonated radical forms B(–H)˙. We also examine the chemical repair reaction by thiols, B(–H)˙(aq)+RSH(aq)=B(aq)+RS˙(aq), where B=A,G,C,T. Our results for the chemical repair of B(–H)˙ suggest that a PT-ET pathway should be favored for A and C at any pH, whereas for G and T, a PT-ET pathway is preferred at acidic and near neutral pH, but in the pH range 9-11, the ET pathway would dominate.

  • 28. Mundim, Maria S. P.
    et al.
    Mocellin, Alessandra
    Makiuchi, Nilo
    Naves de Brito, Arnaldo
    Attie, Marcia
    Correia, Nestor
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Study of thiophene inner shell photofragmentation2007Ingår i: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 155, nr 1-3, s. 58-63Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigated the inner shell photofragmentation of thiophene by time of flight (TOF) mass spectroscopy using multi-coincidence electron-ion techniques. Our main purpose was to understand aspects of molecular relaxation process after inner shell excitation and to search for bond break selectivity. Analyses of mass and branching ratios are presented and the results suggest different mechanisms and channel of fragmentation when compared with S 2p and C 1s excitations.

  • 29.
    Nilsing, Mattias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Avdelningen för kvantkemi.
    Computational Investigation of Dye-Sensitized Solar Cells2007Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Interfaces between semiconductors and adsorbed molecules form a central area of research in surface science, occurring in many different contexts. One such application is the so-called Dye-Sensitized Solar Cell (DSSC) where the nanostructured dye-semiconductor interface is of special interest, as this is where the most important ultrafast electron transfer process takes place. In this thesis, structural and electronic aspects of these interfaces have been studied theoretically using quantum chemical computations applied to realistic dye-semiconductor systems. Periodic boundary conditions and large cluster models have been employed together with hybrid HF-DFT functionals in the modeling of nanostructured titanium dioxide.

    A study of the adsorption of a pyridine molecule via phosphonic and carboxylic acid anchor groups to an anatase (101) surface showed that the choice of anchor group affects the strength of the bindings as well as the electronic interaction at the dye-TiO2 interface. The calculated interfacial electronic coupling was found to be stronger for carboxylic acid than for phosphonic acid, while phosphonic acid binds significantly stronger than carboxylic acid to the TiO2 surface.

    Atomistic and electronic structure of realistic dye-semiconductor interfaces were reported for RuII-bis-terpyridine dyes on a large anatase TiO2 cluster and perylene dyes on a periodic rutile (110) TiO2 surface. The results show strong influence of anchor and inserted spacer groups on adsorption and electronic properties. Also in these cases, the phosphonic acid anchor group was found to bind the dyes significantly stronger to the surface than the carboxylic acid anchor, while the interfacial electronic coupling was stronger for the carboxylic anchor. The estimated electron injection times were twice as fast for the carboxylic anchor compared to the phosphonic anchor. Moreover, the electronic coupling was affected by the choice of spacer group, where unsaturated spacer groups were found to mediate electron transfer more efficiently than saturated ones.