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  • 51. Ekert, Artur
    et al.
    Ericsson, Marie
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Quantum Chemistry. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Quantum Chemistry.
    Hayden, Patrick
    Inamori, Hitoshi
    Jones, Jonathan A.
    Oi, Daniel K.L.
    Vedral, Vlatko
    Geometric quantum computation2000In: Journal of Modern Optics, Vol. 47, p. 2501-Article in journal (Refereed)
    Abstract [en]

    We describe in detail a general strategy for implementing a conditional geometric phase between two spins. Combined with single-spin operations, this simple operation is a universal gate for quantum computation, in that any unitary transformation can be implemented with arbitrary precision using only single-spin operations and conditional phase shifts. Thus quantum geometrical phases can form the basis of any quantum computation. Moreover, as the induced conditional phase depends only on the geometry of the paths executed by the spins it is resilient to certain types of errors and offers the potential of a naturally fault-tolerant way of performing quantum computation.

  • 52.
    Ericsson, Marie
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Holonomic quantum logic gates2002In: Quantum Theory: Reconsideration of Foundations / [ed] A. Khrennikov, 2002, p. 75-81Conference paper (Other academic)
    Abstract [en]

    This is a brief overview of quantum holonomies in the context of quantum computation. We choose an adequate set of quantum logic gates, namely, a phase gate, the Hadamard gate, and a conditional-phase gate and show how they can be implemented by purely geometric means. Such gates may be more resilient to certain types of errors.

  • 53.
    Ericsson, Marie
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Montangero, Simone
    Quantum Information and Many Body Quantum Systems2008Conference proceedings (editor) (Other academic)
  • 54. Forrey, Robert
    et al.
    Cote, Robin
    Dalgarno, Alex
    Jonsell, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Saenz, Alejandro
    Froelich, Piotr
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Collisions between metastable hydrogen atoms at thermal energies2000In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 85, no 20, p. 4245-4248Article in journal (Refereed)
    Abstract [en]

    The complex interaction potentials arising in the approach of two metastable hydrogen 2s atoms are calculated and the cross sections for ionization, excitation transfer, and elastic scattering are predicted. The measured cross section for associative ionization at E = 4.1 meV equals 2×10-15 cm2. We calculate a total ionization cross section of 2×10-13 cm2, varying as E-2/3 at higher energies. Thus it appears that dissociative ionization is the major ionization channel. We find also that double excitation transfer into two excited H(2p) atoms is still more probable with the large cross section of 9×10-12 cm2 at E = 4.1 meV varying as E-1/2 at higher energies. The detection of the resulting Lyman alpha photons would provide a diagnostic test of our predictions.

  • 55.
    Froelich, Piotr
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Quantum chemistry of antimatter2002In: Advances in Quantum Chemistry, ISSN 0065-3276, E-ISSN 2162-8815, Vol. 41, p. 185-202Article in journal (Refereed)
  • 56.
    Froelich, Piotr
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Dalgarno, Alex
    Jonsell, Svante
    Saenz, Alejandro
    Voronin, Alexei
    Zygelman, Bernard
    Antihydrogen in Interaction with Atoms and Surfaces2005In: AIP Conference Proceedings, ISSN 0094-243X, E-ISSN 1551-7616, Vol. 770, no 1, p. 51-67Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Anoverview of the antiatom interactions with matter is given inthe context of the ongoing efforts to trap and coolantihydrogen at CERN. We show how the atom-antiatom scattering can,in addition to annihilation, result in a number of collisionalreactions such as elastic scattering, rearrangement to protonium and positronium,and even radiative association leading to formation of unusual short-livedatom-antiatom molecules. We also show that sufficiently cold antiatoms canbe reflected from material walls. The rates for these reactionsare of interest for the experiments with antihydrogen atoms atCERN, they probe the feasibility of collisional cooling of antihydrogenand they contribute to the understanding of stability of matterin contact with antimatter in general.

  • 57.
    Froelich, Piotr
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Quantum Chemistry. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Kvantkemi.
    Jonsell, Svante
    Saenz, Alejandro
    Eriksson, Stefan
    Zygelman, Bernard
    Dalgarno, Alex
    Leptonic Annihilation in Hydrogen - Antihydrogen Collisions2004In: Phys. Rev. A, Vol. 70, no 022509Article in journal (Refereed)
  • 58.
    Froelich, Piotr
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Quantum Chemistry. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Kvantkemi.
    Jonsell, Svante
    Saenz, Alejandro
    Eriksson, Stefan
    Zygelman, Bernard
    Dalgarno, Alex
    Positron - Electron Annihilation in Hydrogen - Antihydrogen Collisions2004In: Advances in Quantum Chemistry, Vol. 47, p. 465-Article in journal (Refereed)
  • 59.
    Froelich, Piotr
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Jonsell, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Saenz, Alejandro
    Zygelman, Bernard
    Dalgarno, Alex
    Hydrogen - Antihydrogen Collisions2001In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 692, no 1-2, p. 182c-183cArticle in journal (Refereed)
  • 60.
    Froelich, Piotr
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Jonsell, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Saenz, Alejandro
    Zygelman, Bernard
    Dalgarno, Alex
    Hydrogen-antihydrogen collisions2000In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 84, no 20, p. 4577-4580Article in journal (Refereed)
    Abstract [en]

    Matter-antimatter interactions are investigated using hydrogen-antihydrogen collisions as an example. Cross sections for elastic scattering and for the antihydrogen loss (either through the rearrangement reaction, resulting in formation of protonium and positronium according to H+H →pp+1 e+e-, or via annihilation in flight) are calculated for the first time in a fully quantum mechanical approach. Implications for experiments intending to trap and cool antihydrogen are discussed.

  • 61.
    Froelich, Piotr
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Saenz, Alejandro
    Calculation of the beta-decay spectrum of the T-2 molecule beyond the sudden impulse approximation1996In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 77, no 23, p. 4724-4727Article in journal (Refereed)
    Abstract [en]

    The probability distribution of electronic excitations of HeT+ following the beta decay of the T-2 molecule has been calculated for the first time in the beyond sudden impulse approximation, removing the uncertainty related to the reliability of this appr

  • 62.
    Froelich, Piotr
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Wallenius, Jan
    Resonance Sidepath in Muon Catalyzed Fusion1995In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 75, no 11, p. 2108-2111Article in journal (Refereed)
    Abstract [en]

    We have investigated a previously unconsidered sidepath in muon catalyzed fusion. We have found that high formation rates of metastable dt mu* molecules in t mu(2s)-D-2 collisions and their subsequent decay into t mu(1s) or d mu(1s) atoms open a return path for the muon from tritium to deuterium. This process can be considered as muon transfer from tμ(2s) to dμ(1s) via three-body resonances of dtμ*. This enlarges the dμ(1s) population and quenches the muon cycling rate, in agreement with experimental findings.

  • 63.
    Froelich, Piotr
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Quantum Chemistry. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Weyrich, Wolf
    On the relativistic corrections to the cross-section for inelastic scattering of photons on atomic electrons1996In: ZEITSCHRIFT FUR PHYSIK D-ATOMS MOLECULES AND CLUSTERS, ISSN 0178-7683, Vol. 38, no 3, p. 185-190Article in journal (Refereed)
    Abstract [en]

    The relativistic cross-section for inelastic photon scattering on bound electrons is reconsidered, and lowest-order corrections to the sudden-impulse approximation are derived. These corrections stem from including the presence of the external (Coulombic)

  • 64.
    Froelich, Piotr
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Zygelman, Bernard
    Saenz, Alejandro
    Jonsell, Svante
    Eriksson, Stefan
    Dalgarno, Alex
    Hydrogen: Antihydrogen Molecule and its Properties2004In: Few-body systems, ISSN 0177-7963, E-ISSN 1432-5411, Vol. 34, no 1-3, p. 63-72Article in journal (Refereed)
    Abstract [en]

    The metastability of the four-body system is discussed from the point of view of radiative rearrangement collisions of the hydrogen and antihydrogen. Such collisions lead to the formation of an intermediate molecular state which further decays into positronium and protonium or is destroyed via annihilation. We present calculations of the lifetime of the system and the branching ratios for Coulombic decay and annihilation.

  • 65. Gonzalez-Ramirez, Israel
    et al.
    Roca-Sanjuán, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Climent, Teresa
    Serrano-Perez, Juan Jose
    Merchan, Manuela
    Serrano-Andres, Luis
    On the photoproduction of DNA/RNA cyclobutane pyrimidine dimers2011In: Theoretical Chemistry accounts, ISSN 1432-881X, E-ISSN 1432-2234, Vol. 128, no 4-6, p. 705-711Article in journal (Refereed)
    Abstract [en]

    The UV photoreactivity of different pyrimidine DNA/RNA nucleobases along the singlet manifold leading to the formation of cyclobutane pyrimidine dimers has been studied by using the CASPT2 level of theory. The initially irradiated singlet state promotes the formation of excimers between pairs of properly oriented nucleobases through the overlap between the pi structures of two stacked nucleobases. The system evolves then to the formation of cyclobutane pyrimidine dimers via a shearing-type conical intersection activating a [2 + 2] photocycloaddition mechanism. The relative location of stable excimer conformations or alternative decay channels with respect to the reactive degeneracy region explains the differences in the photoproduction efficiency observed in the experiments for different nucleobases sequences. A comparative analysis of the main structural parameters and energetic profiles in the singlet manifold is carried out for thymine, uracil, cytosine, and 5-methylcytosine homodimers. Thymine and uracil dimers display the most favorable paths, in contrast to cytosine. Methylation of the nucleobases seems to increase the probability for dimerization.

  • 66.
    Hennies, Franz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Pietzsch, Annette
    Berglund, Martin
    Föhlisch, Alexander
    Schmitt, Thorsten
    Strocov, Vladimir
    Karlsson, Hans O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Andersson, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Resonant Inelastic Scattering Spectra of Free Molecules with Vibrational Resolution2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 104, no 19, p. 193002-Article in journal (Refereed)
    Abstract [en]

    Inelastic x-ray scattering spectra excited at the 1s(-1) pi* resonance of gas phase O-2 have been recorded with an overall energy resolution that allows for well-resolved vibrational progressions. The nuclear wave packet dynamics in the intermediate state is reflected in vibrational excitations of the electronic ground state, and by fine-tuning the excitation energy the dissociation dynamics in the predissociative B' (3) Pi(g) final state is controlled.

  • 67.
    Henningsson, Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Stashans, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Södergren, Sven
    Lindström, H.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Vayssieres, L.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Lunell, Sten
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry. Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Proton insertion in polycrystalline WO3 studied with electron spectroscopy and semi-empirical calculations2004In: Advances in Quantum Chemistry, ISSN 0065-3276, E-ISSN 2162-8815, Vol. 47, p. 23-36Article in journal (Refereed)
  • 68. Huber, Stefan M.
    et al.
    Ertem, Mehmed Z.
    Aquilante, Francesco
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Gagliardi, Laura
    Tolman, William B.
    Cramer, Christopher J.
    Generating Cu-II-oxyl/Cu-III-oxo species from Cu-I-alpha-ketocarboxylate complexes and O-2: in silico studies on ligand effects and C-H-activation reactivity.2009In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, no 19, p. 4886-4895Article in journal (Refereed)
    Abstract [en]

    A mechanism for the oxygenation of Cu-I complexes with alpha-keto-carboxylate ligands that is based on a combination of density functional theory and multireference second-order perturbation theory (CASSCF/CASPT2) calculations is elaborated. The reaction proceeds in a manner largely analogous to those of similar Fe-II-alpha-ketocarboxylate systems, that is, by initial attack of a coordinated oxygen molecule on a ketocarboxylate ligand with concomitant decarboxylation. Subsequently, two reactive intermediates may be generated, a Cu-peracid structure and a [CuO](+) species, both of which are capable of oxidizing a phenyl ring component of the supporting ligand. Hydroxylation by the [CuO](+) species is predicted to proceed with a smaller activation free energy. The effects of electronic and steric variations on the oxygenation mechanisms were studied by introducing substituents at several positions of the ligand backbone and by investigating various N-donor ligands. In general, more electron donation by the N-donor ligand leads to increased stabilization of the more Cu-II/Cu-III-like intermediates (oxygen adducts and [CuO](+) species) relative to the more Cu-I-like peracid intermediate. For all ligands investigated the [CuO](+) intermediates are best described as Cu-II-O center dot(-) species with triplet ground states. The reactivity of these compounds in C-H abstraction reactions decreases with more electron-donating N-donor ligands, which also increase the Cu-O bond strength, although the Cu-O bond is generally predicted to be rather weak (with a bond order of about 0.5). A comparison of several methods to obtain singlet energies for the reaction intermediates indicates that multireference second-order perturbation theory is likely more accurate for the initial oxygen adducts, but not necessarily for subsequent reaction intermediates.

  • 69. Huber, Stefan M.
    et al.
    Shahi, Abdul Rehaman Moughal
    Aquilante, Francesco
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Cramer, Christopher J.
    Gagliardi, Laura
    What Active Space Adequately Describes Oxygen Activation by a Late Transition Metal?: CASPT2 and RASPT2 Applied to Intermediates from the Reaction of O-2 with a Cu(I)-alpha-Ketocarboxylate2009In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 5, no 11, p. 2967-2976Article in journal (Refereed)
    Abstract [en]

    Multiconfigurational second-order perturbation theory calculations based on a complete active space reference wave function (CASPT2), employing active spaces of increasing size, are well converged at the level of 12 electrons in 12 orbitals for the singlet-triplet state-energy splittings of three supported copper-dioxygen and two supported copper-oxo complexes. Corresponding calculations using the restricted active space approach (RASPT2) offer similar accuracy with a significantly reduced computational overhead provided an inner (2,2) complete active space is included in the overall RAS space in order to account for strong biradical character in most of the compounds. The effects of the different active space choices and the outer RAS space excitations are examined, and conclusions are drawn with respect to the general applicability of the RASPT2 protocol.

  • 70.
    Itagaki, Y.
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Quantum Chemistry. Department of Physics. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Wang, P.
    Isamoto, N.
    Shiotani, M.
    Hasegawa, A.
    Jansson, M.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Quantum Chemistry. Department of Physics. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Lunell, S.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Quantum Chemistry. Department of Physics. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Static and dynamic structures of halogenated dimethyl ether radical cations: An EPR and MO Study2002In: Phys. Chem. Chem. Phys., Vol. 4, p. 2524-2529Article in journal (Refereed)
  • 71.
    Johansson, Markus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Ericsson, Marie
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Singh, Kuldip
    Centre for Quantum Technologies, NUS, Singapore.
    Sjöqvist, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Williamson, Mark S.
    Centre for Quantum Technologies, NUS, Singapore.
    Correlation-induced non-Abelian quantum holonomies2011In: Journal of Physics A: Mathematical and General, ISSN 0305-4470, E-ISSN 1361-6447, Vol. 44, no 14, p. 145301-Article in journal (Refereed)
    Abstract [en]

    In the context of two-particle interferometry, we construct a parallel transport condition that is based on the maximization of coincidence intensity with respect to local unitary operations on one of the subsystems. The dependence on correlation is investigated and it is found that the holonomy group is generally non-Abelian, but Abelian for uncorrelated systems. It is found that our framework contains the Lévay geometric phase (2004 J. Phys. A: Math. Gen. 37 1821) in the case of two-qubit systems undergoing local SU(2) evolutions.

  • 72.
    Johansson, Markus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Ericsson, Marie
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Singh, Kuldip
    Centre for Quantum Technologies, NUS, Singapore.
    Sjöqvist, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Williamson, Mark S.
    Centre for Quantum Technologies, NUS, Singapore.
    Topological phases and multiqubit entanglement2012In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 85, no 3, p. 032112-1-032112-11Article in journal (Refereed)
    Abstract [en]

    Global phase factors of topological origin, resulting from cyclic local $\rm{SU}$ evolution, called topological phases, were first described in [Phys. Rev. Lett. {\bf 90}, 230403 (2003)], in the case of entangled qubit pairs. In this paper we investigate topological phases in multi-qubit systems as the result of cyclic local $\rm{SU(2)}$ evolution. These phases originate from the topological structure of the local $\rm{SU(2)}$-orbits and are an attribute of most entangled multi-qubit systems. We discuss the relation between topological phases and SLOCC-invariant polynomials and give examples where topological phases appear. A general method to find the values of the topological phases in an $n$-qubit system is described and a complete list of these phases for up to seven qubits is given.

  • 73.
    Johansson, Markus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Sjöqvist, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Andersson, Mauritz
    Dept. of Applied Physics, KTH, Sweden.
    Ericsson, Marie
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Hessmo, Björn
    Centre for Quantum Technologies, NUS, Singapore.
    Singh, Kuldip
    Centre for Quantum Technologies, NUS, Singapore.
    Tong, Dianmin
    Physics Dept., Shandong University, China.
    Robustness of nonadiabatic holonomic gates2012In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 86, no 6, p. 062322-Article in journal (Refereed)
    Abstract [en]

    The robustness to different sources of error of the scheme for non-adiabatic holonomic gates proposed in [arXiv:1107.5127v2] is investigated. Open system effects as well as errors in the driving fields are considered. It is found that the gates can be made more error resilient by using sufficiently short pulses. The principal limit of how short the pulses can be made is given by the breakdown of the quasi-monochromatic approximation. A comparison with the resilience of adiabatic gates is carried out.

  • 74. Jonsell, Svante
    et al.
    Forrey, Robert
    Saenz, Alejandro
    Froelich, Piotr
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Fine Structure in Cold Collisions of Spin-Polarized H(2s) Atoms2004In: Physica scripta. T, ISSN 0281-1847, Vol. T110, p. 299-301Article in journal (Refereed)
    Abstract [en]

    We have calculated cross sections and rate coefficients for elastic scattering, ionization, and double excitation transfer in collision of two hydrogen atoms in the 2s state. We find that for collision energies between 5 × 10-10 a.u. and 10-6 a.u. elastic scattering has the largest cross section. For temperatures below 0.02 K ionization is the dominant loss process, while for higher temperatures double excitation transfer dominates. Our results for the total loss rate are found to be within a factor 2 or 3 of the error bars of recent measurements.

     

  • 75. Jonsell, Svante
    et al.
    Froelich, Piotr
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Eriksson, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Strasburger, Krzysztof
    Strong Nuclear Force in Cold Antihydrogen: Helium Collisions2004In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 70, no 6, p. 062708-Article in journal (Refereed)
    Abstract [en]

    We calculate cross sections for elastic scattering and annihilation in antihydrogen-helium collisions at low energies. The calculations are based on the Born-Oppenheimer approximation, and incorporate the effects of the strong interaction through a scattering length approach. We find that the strong nuclear force not only causes significant annihilation, but also cannot be neglected in the elastic channel. In the zero energy limit we obtain the scattering length a=−7.69−3.80i a.u. for ground state antihydrogen-helium collisions. Annihilation is found to dominate over elastic scattering up to a temperature about 3 K. Loosely bound metastable antihydrogen-helium states are also investigated, and it is found that a number of relatively long-lived states with up to three units of angular momentum exist.

  • 76. Jonsell, Svante
    et al.
    Saenz, Alejandro
    Froelich, Piotr
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Low energy hydrogen-antihydrogen collisions2000In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 663-664, p. 959C-962CArticle in journal (Refereed)
    Abstract [en]

    The ground-state interaction potential between hydrogen and antihydrogen has been calculated within the Born-Oppenheimer approximation. Cross sections for rearrangement and annihilation in flight have been determined. Implications for cooling of antihydro

  • 77. Jonsell, Svante
    et al.
    Saenz, Alejandro
    Froelich, Piotr
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Neutrino-mass determination from tritium beta decay: Corrections to and prospects of experimental verification of the final-state spectrum1999In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 60, no 3, p. 34601-Article in journal (Other academic)
    Abstract [en]

    We have investigated the final-state spectrum of HeT+ and HeH+ following beta decay of T-2 or TH. For the electronically bound-state part of the spectrum the effects of a corrected recoil, improved potential curves for the excited states, nonadiabatic eff

  • 78. Jonsell, Svante
    et al.
    Saenz, Alejandro
    Froelich, Piotr
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Non-adiabatic couplings between the final states of tritium beta decay1998In: Polish Journal of Chemistry, ISSN 0137-5083, Vol. 72, no 7, p. 1323-1333Article in journal (Other academic)
    Abstract [en]

    The non-adiabatic couplings between the ground state and the first 5 excited states in (HeT+)-He-3 have been calculated. Non-adiabatic corrections to the beta-decay spectrum of T-2 are derived in first-order perturbation theory. These corrections are esti

  • 79. Jonsell, Svante
    et al.
    Saenz, Alejandro
    Froelich, Piotr
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Zygelman, Bernard
    Dalgarno, Alex
    Including the strong nuclear force in antihydrogen-scattering calculations2005In: Canadian journal of physics (Print), ISSN 0008-4204, E-ISSN 1208-6045, Vol. 83, no 4, p. 435-445Article in journal (Refereed)
    Abstract [en]

    We investigate two methods to include the strong nuclear force in hydrogen-antihydrogen scattering calculations. First, we construct a model optical potential with parameters determined by the measured shift and width of the protonium ground state. Although this potential is a very crude model for the strong nuclear force, its parameters may be adjusted to reproduce both bound states and low-energy annihilation cross sections to within the experimental accuracy. It is then shown that this potential may be reduced to a short-distance boundary condition in terms of the proton-antiproton strong-interaction scattering length. Elastic and annihilation cross sections for ground-state hydrogen-antihydrogen scattering are calculated for s- and p-waves, and collision energies up to 1 atomic unit. The two methods are found to agree to within about 1%. The main source of discrepancy is that the scattering-length approach does not account for vacuum polarization, relativistic, and finite-size corrections. We verify that the range of the strong interaction potential does not affect the hydrogen-antihydrogen s-wave scattering properties, and that the strong interaction has negligible influence on p-wave scattering.

  • 80. Jonsell, Svante
    et al.
    Saenz, Alejandro
    Froelich, Piotr
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Zygelman, Bernard
    Dalgarno, Alex
    Stability of hydrogen-antihydrogen mixtures at low energies2001In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 64, no 5, p. 052712-Article in journal (Refereed)
    Abstract [en]

    The stability of antimatter in contact with matter has been investigated. The interaction between hydrogen and antihydrogen is considered as the prototype reaction. We have focused interest on the rates for proton-antiproton and/or electron-positron annih

  • 81. Jonsell, Svante
    et al.
    Saenz, Alejandro
    Froelich, Piotr
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Zygelman, Bernard
    Dalgarno, Alexei
    Hydrogen: Antihydrogen Scattering in the Born-Oppenheimer Approximation2004In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 37, no 6, p. 1195-Article in journal (Refereed)
    Abstract [en]

    We calculate the low-energy scattering between hydrogen and antihydrogen atoms in their ground states using the Born–Oppenheimer approximation. Improved results for rearrangement, direct annihilation and elastic scattering are presented. The elastic cross section agrees well with other calculations. For the rearrangement process we confirm a recent result (Armour E A G and Chamberlain C W 2002 J. Phys. B: At. Mol. Opt. Phys. 35 L489) that rearrangement to the N = 23 state of protonium has a larger cross section than rearrangement to the N = 24 state. For both rearrangement cross sections our results are smaller than those obtained by Armour and Chamberlain. The direct annihilation, and its influence on elastic scattering, is calculated using the scattering length for the strong force between the proton and antiproton. This approach gives strong-force effects qualitatively similar, but smaller than those obtained in another recent work (Voronin A Yu and Carbonell J 2001 Nucl. Phys. A 689 529c).

  • 82.
    Karlsson, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Borg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Lunell, Sten
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Davidsson, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Karlsson, Hans O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Experimental and theoretical study of the photodissociation of bromo-3-fluorobenzene2008In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 128, no 3, p. 034307-Article in journal (Refereed)
    Abstract [en]

    The UV photodissociation of bromo-3-fluorobenzene under collisionless conditions has been studied as a function of the excitation wavelength between 255 and 265 nm. The experiments were performed using ultrafast pump-probe laser spectroscopy. To aid in the interpretation of the results, it was necessary to extend the theoretical framework substantially compared to previous studies, to also include quantum dynamical simulations employing a two-dimensional nuclear Hamiltonian. The nonadiabatic potential energy surfaces (PES) were parameterized against high-level MS-CASTP2 quantum chemical calculations, using both the C–Br distance and the out-of-plane bending of the bromine as nuclear parameters. We show that the wavelength dependence of the photodissociation via the S01ππ*1πσ* channel, accessible with a ∼ 260 nm pulse, is captured in this model. We thereby present the first correlation between experiments and theory within the quantitative regime.

  • 83.
    Karlsson, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Reduced-order modeling, error estimation, and the role of the start-vector: The recursive residue generation method revisited2007In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 111, no 41, p. 10263-10268Article in journal (Refereed)
    Abstract [en]

    The recursive residue generation method (RRGM) [Wyatt, R. E. Adv. Chem. Phys. 1989, 73, 231] is rederived using the formalism of reduced-order modeling [Bai, Z. Appl. Numerical Math. 2002, 43, 9]. A stopping criteria for the RRGM recursions is proposed, on the basis of an expression for an upper bound to the absolute error [B ai, Z.; Ye, Q. Electron. Trans. Numerical Anal. 1998, 7, 1]. It is further pointed out that, in general, the start-vector has a negligible effect on the convergence of the RRGM.

  • 84.
    Karlsson, Hans
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Nyström, IngelaUppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Centre for Image Analysis. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis.
    UPPMAX Progress Report2008Collection (editor) (Other (popular science, discussion, etc.))
  • 85.
    Karlsson, Hans O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Accelerating the convergence of the Lanczos algorithm by the use of a complex symmetric Cholesky factorization: application to correlation functions in quantum molecular dynamics2011In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 44, no 20, p. 205102-Article in journal (Refereed)
    Abstract [en]

    The theoretical description of reactive scattering, photo dissociation and a number of other problems in chemical physics can be formulated in terms of a correlation function between an initial and final state. It is shown by example that the convergence of correlation functions computed using a complex symmetric Lanczos algorithm can be significantly accelerated by using a complex symmetric version of the Cholesky decomposition. In fact, using the standard Lanczos approach without the Cholesky transformation, the correlation function might not converge at all. It is further demonstrated that a stopping criterion for the Lanczos recursions, based on an estimate for the upper bound of the error of the correlation function, can be extended to complex symmetric matrices and used as a reliable stopping criterion for the Cholesky-Lanczos approach.

  • 86.
    Karlsson, Hans O
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Accurate resonances and effective absorption of flux using smooth exterior scaling1998In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 109, no 21, p. 9366-9371Article in journal (Refereed)
    Abstract [en]

    A general coordinate transformation is used to derive smooth exterior scaling (SES). Different complex paths are discussed and it is also shown how to derive a complex absorbing potential (CAP) from the SES. Accurate resonance values are computed both for short range and long range potentials. It is shown that the SES absorbs outgoing flux very effectively. The approximation of not scaling the potential and its relation to CAPs is discussed. It is emphasized that the SES can be implemented as easy as CAPs for grid methods.

  • 87.
    Karlsson, Hans O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Calculation of highly excited vibrational states using a Richardson-Leja-Davidson scheme2007In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 126, no 8, p. 084105-Article in journal (Refereed)
    Abstract [en]

    An efficient computational scheme for calculating highly excited vibrational eigenstates is proposed, combining a Richardson-Leja spectral filter with a novel version of the Davidson method [J. Comput. Phys. 17, 87 (1975)]. Highly excited eigenstates of the Rb-2 and H2O molecules are computed to test and verify the method. On the average less than 2.5 outer recursions per eigenstate are needed. For each outer Davidson recursion, less than 20 inner filter recursions per eigenstate are needed on the average.

  • 88.
    Karlsson, Hans O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Stability of the complex symmetric Lanczos algorithm for computing photodissociation cross sections using smooth exterior scaling or absorbing potentials.2009In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 42, no 12, p. 125205-Article in journal (Refereed)
    Abstract [en]

    The stability of the Lanczos algorithm for computing photodissociation cross sections is studied. The system is discretized on a grid and the discrete variable representation (DVR) is used to represent system operators. The Hamiltonian is augmented with an absorbing potential (AP) or smooth exterior scaling (SES), to enforce outgoing boundary conditions, making it complex symmetric. The main difference between the AP and the SES is that the former adds to the potential energy whereas the latter modifies the kinetic energy operator. Grozdanov et al (2004 J. Phys. B: At. Mol. Opt. Phys. 31 173) observed the fact that the Lanczos recursions could slow down and even stagnate for certain choices of parameters in the AP or SES. Here we show that for the SES, it is important that the maximum kinetic energy of the DVR is adapted to the physical problem or else the Lanczos recursions might be unstable. A similar result was found for the AP; that is, the Lanczos algorithm in order to converge the strength of the absorbing potential should be of the order of the scattering energy of interest. It is shown that with a discretization adopted to the physical problem at hand and a proper choice of parameters, the Lanczos recursions converge and provide accurate results for both the absorbing potential and the smooth exterior scaling.

  • 89.
    Karlsson, Hans O.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Holmgren, Sverker
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis.
    Cross correlation functions Cnm(E) via Lanczos algorithms without diagonalization2002In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 117, p. 9116-9123Article in journal (Refereed)
  • 90.
    Kay, Alastair
    et al.
    Centre for Quantum Computation, DAMTP, Univ. of Cambridge, UK.
    Ericsson, Marie
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Geometric Effects and Computation in Spin Networks2005In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 7, p. 143-Article in journal (Refereed)
    Abstract [en]

    When initially introduced, a Hamiltonian that realises perfect transfer of a quantum state was found to be analogous to an x-rotation of a large spin. In this paper we extend the analogy further to demonstrate geometric effects by performing rotations on the spin. Such effects can be used to determine properties of the chain, such as its length, in a robust manner. Alternatively, they can form the basis of a spin network quantum computer. We demonstrate a universal set of gates in such a system by both dynamical and geometrical means.

  • 91.
    Kay, Alastair
    et al.
    Centre for Quantum Computation, DAMTP, Univ. Cambridge, UK.
    Ericsson, Marie
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Local Cloning of Arbitrarily Entangled Multipartite States2006In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 73, no 1, p. 012343-Article in journal (Refereed)
    Abstract [en]

    We examine the perfect cloning of non-local, orthogonal states with only local operations and classical communication. We provide a complete characterisation of the states that can be cloned under these restrictions, and their relation to distinguishability. We also consider the case of catalytic cloning, which we show provides no enhancement to the set of clonable states.

  • 92. Kino, Yasushi
    et al.
    Yamanaka, Nobuhiro
    Froelich, Piotr
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Coupled Rearrangement Channel Calculation of the Hyperfine Structure of the dtmu Molecule2001In: Hyperfine Interactions, ISSN 0304-3843, E-ISSN 1572-9540, Vol. 138, no 1-4, p. 281-284Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Hyperfine structure splittings are calculated for the J = v = 1 state of the dtμ molecule. The splittings are determined by the accurate three-body wave function obtained by coupled rearrangement channel method using the updated physical constants. The result obtained is in good agreement with the previous calculation within ∼0.07 meV. The discrepancy is due to the accuracy of the three-body wave function.

  • 93. Kino, Yasushi
    et al.
    Yamanaka, Nobuhiro
    Kamimura, Masao
    Froelich, Piotr
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Quantum Chemistry. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Kudo, H
    Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    High-Precision Calculation of the Energy Levels and Auger Decay Rates of the Metastable States of the Antiprotonic Helium Atoms2001In: Hyperfine Interactions, Vol. 138, p. 179-Article in journal (Other (popular scientific, debate etc.))
  • 94. Kloda, Tomasz
    et al.
    Matsuda, Akitaka
    Karlsson, Hans O
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Elshakre, Mohamed
    Linusson, Per
    Eland, John H. D.
    Feifel, Raimund
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Hansson, Tony
    Strong-field photoionization of O2 at intermediate light intensity2010In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 82, no 3, p. 033431-Article in journal (Refereed)
    Abstract [en]

    We investigated by electron spectroscopy the strong-field multiphoton ionization of O-2 molecules with ultrashort laser pulses in the intensity range between the multiphoton and tunneling regimes. The ionization proceeds by at least three different mechanisms, in addition to the eight- and nine-photon nonresonant pathways. Transient multiphoton resonances with vibrational Rydberg levels give rise to direct Freeman-type peaks with sublaser linewidth and spin-orbit splitting. Some resonance levels actually become populated and yield extremely narrow lines because of postpulse vibrational autoionization. When the lowest photon order resonance channel for the Rydberg states is closed, a third contribution becomes dominant with a main peak at 0.4 eV that shares its main properties with the recently discovered universal low-energy structure in the electron spectra of atoms and molecules [C. I. Blaga et al., Nat. Phys. 5, 335 (2009); W. Quan et al., Phys. Rev. Lett. 103, 093001 (2009)]. The variation of the Freeman resonance spectrum with the laser peak intensity is well correlated with the vibronic Franck-Condon factors for the overlap of the intermediate Rydberg state with the O-2 ground state. Accordingly, the Freeman peaks could be unambiguously assigned to individual vibronic multiphoton resonances, and the disappearance of the Freeman resonances at a certain laser intensity could be explained. The population of the autoionizing Rydberg states could be assigned similarly to such vibronic resonances.

  • 95. Komaguchi, Kenji
    et al.
    Nomura, K.
    Shiotani, Masaru
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Lund, Anders
    Jansson, Magnus
    Physics, Department of Quantum Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry. Kvantkemi.
    Lunell, Sten
    Physics, Department of Quantum Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry. Quantum Chemistry.
    ESR and theoretical studies of trimer radical cations of coronene2006In: Spectrochimica Acta A, Vol. 63, p. 76-Article in journal (Refereed)
  • 96. Komaguchi, Kenji
    et al.
    Norberg, Daniel
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Quantum Chemistry. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry. Kvantkemi.
    Nakazawa, Naoko
    Shiotani, Masaru
    Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Persson, Petter
    Department of Physical Chemistry. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Avdelningen för kvantkemi.
    Lunell, Sten
    Department of Physical Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Quantum Chemistry. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Avdelningen för kvantkemi.
    Direct ESR evidence for SH2 type reaction of methyl radical with methylsilane and methylgermane in a low temperature solid: A deuterium labeling study2005In: Chemical Physics Letters, Vol. 410, no 1-3, p. 1-5Article in journal (Refereed)
  • 97.
    Kormann, Katharina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computational Science.
    Holmgren, Sverker
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computational Science.
    Karlsson, Hans O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    A Fourier-coefficient based solution of an optimal control problem in quantum chemistry2010In: Journal of Optimization Theory and Applications, ISSN 0022-3239, E-ISSN 1573-2878, Vol. 147, p. 491-506Article in journal (Refereed)
  • 98.
    Kormann, Katharina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computational Science.
    Holmgren, Sverker
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computational Science.
    Karlsson, Hans O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    A Fourier-coefficient based solution of an optimal control problem in quantum chemistry2009Report (Other academic)
  • 99.
    Kormann, Katharina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computational Science.
    Holmgren, Sverker
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computational Science.
    Karlsson, Hans O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Accurate time propagation for the Schrödinger equation with an explicitly time-dependent Hamiltonian2008In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 128, p. 184101:1-11Article in journal (Refereed)
  • 100.
    Kormann, Katharina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computational Science.
    Holmgren, Sverker
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computational Science.
    Karlsson, Hans O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Global error control of the time-propagation for the Schrödinger equation with a time-dependent Hamiltonian2009Report (Other academic)
12345 51 - 100 of 215
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