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  • 1. Andersson, L M
    et al.
    Aberg, J
    Karlsson, H O
    Goscinski, O
    Properties of a discretized coherent state representation and the relation to Gabor analysis2002In: Journal of Physics A: Mathematical and General, ISSN 0305-4470, E-ISSN 1361-6447, Vol. 35, no 36, 7787-7801 p.Article in journal (Refereed)
    Abstract [en]

    Properties of a discretized coherent state representation (DCSR) and its connection to Gabor frame analysis are discussed. The DCSR approach was recently shown (Andersson L M 2001 J. Chem. Phys. 115 1158) to yield a practical computational scheme for quantum dynamics, and an iterative scheme for finding the identity operator was proposed. In the present work, we suggest a proof of fast convergence of the iterative scheme for computing the canonical dual to any given countable frame in a Hilbert space. The method of frames is concerned with the use of a non-orthogonal, over-complete set of functions for expansion of an arbitrary function. We also introduce the concept of 'representations of the identity operator' and show how to expand arbitrary vectors using the frame elements, without explicit diagonalization to an orthonormal basis. Numerical examples that illustrate the method are shown.

  • 2. Andersson, L M
    et al.
    Burmeister, F
    Karlsson, H O
    Goscinski, O
    Nonadiabatic effects in the photoelectron spectra of HCl and DCl. II. Theory2002In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 65, no 1, 012705- p.Article in journal (Refereed)
    Abstract [en]

    The vibrationally resolved photoelectron spectra of HCl and DCl in the 25-28 eV region were computed using a time-dependent approach for the nuclear dynamics. The spectral features cannot be understood without including a nonadiabatic coupling between the dissociative 3 (2)Sigma(+) state and the bound 4 (2)Sigma(+) state in the adiabatic picture. Alternatively, in the diabatic picture a dissociative two-hole-one-particle state interacts with a bound one-hole state. The molecular system is of intermediate coupling strength, i.e., it cannot be described by a single potential-energy curve. The interaction between a bound and a dissociative state leads to Fano resonances superimposed on a broad back-round, as observed in the experimental spectra [Burmeister et al., Phys. Rev. A 65, 012704 (2001)]. From modified potential-energy curves, all features of the experimental spectra, including Fano resonance parameters and lifetimes, were reproduced. From the simulations we observe that two additional peaks in the experimental DCl spectra should appear if the resolution were to be enhanced to around 10 meV.

  • 3.
    Andersson, L Mauritz
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Quantum Chemistry.
    Burmeister, Florian
    Karlsson, Hans
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Quantum Chemistry.
    Nonadiabtic effects in the photoelectron spectra of HCl and DCl II: Theory2002In: Physical Review A, Vol. 65, no 1, 012705- p.Article in journal (Refereed)
  • 4.
    Andersson, LM
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Karlsson, Hans O
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Goscinski, Osvaldo
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Berg, Lars-Erik
    Beutter, Matthias
    Hansson, Tony
    Vibrational wave packet dynamics in NaK: The A (1)Sigma(+) state1999In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 241, no 1, 43-54 p.Article in journal (Refereed)
    Abstract [en]

    A combined experimental and theoretical study of the vibrational wave packet dynamics for the NaK molecule in the A (1)Sigma(+) state is presented. The experiment utilises a 790 nm one-colour femtosecond pump-probe scheme with detection of a previously nor reported dissociation pathway of the 3 (1)Pi(+) state, leading to the Na(3p) + K(4s) product channel. The dissociation is suggested to proceed via either collisionally mediated processes or a molecular cascading process via the 4 (1)Sigma(+) state, which crosses several states correlating to the Na(3p) + K(4s) limit. Time-dependent quantum mechanical calculations are used for studying the dynamics in detail. Simulations are performed both for 790 nm and for 766 nm, to relate also to earlier studies. The previous interpretations of the probe processes are revised. Inclusion of vibrational and rotational temperature effects are shown to be crucial for explaining the shape of the signal and the vibrational period, and leads to excellent agreement with the experiments.

  • 5. Burmeister, F
    et al.
    Andersson, L M
    Ohrwall, G
    Richter, T
    Zimmermann, P
    Godehusen, K
    Martins, M
    Karlsson, H O
    Sorensen, S L
    Bjorneholm, O
    Feifel, R
    Wiesner, K
    Goscinski, O
    Karlsson, L
    Svensson, S
    Yencha, A J
    A study of the inner-valence ionization region in HCl and DCl2004In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 37, no 6, 1173-1183 p.Article in journal (Refereed)
    Abstract [en]

    An in-depth photoionization study of the inner-valence electrons in HCl and DCl has been performed using synchrotron radiation. A series of photoelectron spectra of HCl were obtained at a resolution of 23 meV over the binding energy range 25-30.5 eV at various excitation energies and at two different electron collection angles relative to the plane of polarization of the undulator radiation. In addition, photoelectron spectra of DCl were recorded at two different excitation energies. These spectra were compared directly with the threshold photoelectron spectra of HCl and DCl that were recorded previously under similar resolution conditions (similar to30 meV). This comparative study reveals new information on the nature of the numerous band systems observed in this binding energy region. In addition, we present the experimental confirmation of the theoretical prediction given by Andersson et al (2001 Phys. Rev. A 65 012705) that a vibrational progression showing interference structure would appear in the main inner-valence ionization band in the photoelectron spectrum of DCl at a resolution of 10 meV.

  • 6.
    Burmeister, F. ,..Feifel,.R., Karlsson, L. and Svensson, S.
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Department of Physics and Materials Science, Physics II.
    Andersson, L. Mauritz
    Department of Quantum Chemistry. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Department of Physics and Materials Science, Physics II.
    Karlsson, Hans
    Department of Quantum Chemistry. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Department of Physics and Materials Science, Physics II.
    Goscinski, Osvaldo
    Department of Quantum Chemistry. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Department of Physics and Materials Science, Physics II.
    Confirmation of non adiabatic vibrational progression in the inner valence 4sigmaminus photoionization band of DCl and HCl2002In: Phys Rev AArticle in journal (Refereed)
  • 7.
    Burmeister, Florian
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Physics V.
    Andersson, L M
    Department of Quantum Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Physics V.
    Richter, T
    Zimmerman, P
    Godehusen, K
    Karlsson, Hans
    Department of Quantum Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Physics V.
    Sorensen, S L
    Björneholm, Olle
    Department of Physics. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Physics V.
    Feifel, Raimund
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Physics V.
    Wiesner, Karoline
    Department of Physics. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Physics V.
    Goscinski, Osvaldo
    Department of Quantum Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Physics V.
    Karlsson, Leif
    Department of Physics. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Physics V.
    Svensson, Svante
    Department of Physics. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Physics V.
    A study of the inner-valence ionization region in HCl and DCl2004In: Journal of Physics B: At. Mol. Opt. Phys., Vol. 37, 1173- p.Article in journal (Refereed)
  • 8.
    Farahani, Pooria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Karlsson, Hans O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Ab initio quantum mechanical calculation of the reaction probability for the Cl- + PH2Cl -> ClPH2 + Cl- reaction2013In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 425, 134-140 p.Article in journal (Refereed)
    Abstract [en]

    The SN2 substitution reactions at phosphorus play a key role in organic and biological processes. Quantum molecular dynamics simulations have been performed to study the prototype reaction Cl-+PH2ClClPH2+Cl-, using one and two-dimensional models. A potential energy surface, showing an energy well for a transition complex, was generated using ab initio electronic structure calculations. The one-dimensional model is essentially reflection free, whereas the more realistic two-dimensional model displays involved resonance structures in the reaction probability. The reaction rate is almost two orders of magnitude smaller for the two-dimensional compared to the one-dimensional model. Energetic errors in the potential energy surface is estimated to affect the rate by only a factor of two. This shows that for these types of reactions it is more important to increase the dimensionality of the modeling than to increase the accuracy of the electronic structure calculation.

  • 9.
    Fernández Galván, Ignacio
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Karlsson, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Stenrup, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Lindh, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Quantum dynamics simulations of model chemiluminescence systems2014In: Luminescence (Chichester, England Print), ISSN 1522-7235, E-ISSN 1522-7243, Vol. 29, no S1, 67-67 p.Article in journal (Other academic)
  • 10. Gador, N
    et al.
    Zhang, B
    Karlsson, H O
    Hansson, T
    Dynamical interference structures in fully coupled bound-bound state quantum wave-packet dynamics2004In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 70, no 3, 033418- p.Article in journal (Refereed)
    Abstract [en]

    The quantum wave-packet dynamics in a bound-bound state system at intermediate coupling strength, the A and b states in the Rb-2 molecule coupled by spin-orbit interaction, was studied by ultrafast pump-probe molecular beam spectrocopy and quantum dynamical calculations. It was shown that even at elevated molecular temperatures the experimentally observed traces are characterized by dynamical interference structures of mesobatic, i.e., diabatic-adiabatic hybrid, kind. Two types of mesobatic motion were discerned: bistable, which occurs in both bound-unbound and bound-bound systems, and astable, which is particular to bound-bound systems at intermediate coupling strength. Contrary to previous expectations, the signatures of the quantum interference structures in pump-probe delay traces were found to be robust toward averaging over initial quantum states. It was shown that the spectral variations observed while tuning the pump pulse wavelength is a quantum matter-wave relative of the fringes observed in a pulsed optical Michelson interferometer.

  • 11. Gador, Niklas
    et al.
    Zhang, Bo
    Karlsson, Hans
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Quantum Chemistry.
    Hansson, Tony
    Dynamical interference structures in fully coupled bound-bound state quantum wave-packet dynamics2004In: Physical Review A, Vol. 70, no 3, 033418- p.Article in journal (Refereed)
  • 12.
    Hast, Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Visual Information and Interaction. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis and Human-Computer Interaction.
    Hanke, Michael
    Royal Inst Technol, KTH, Dept Math, Sch Engn Sci, Stockholm, Sweden.
    Karlsson, Hans O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Swedish eScience Education – a Graduate School in eScience2015In: Proc. 11th International Conference on e-Science, IEEE Computer Society, 2015, 31-35 p.Conference paper (Refereed)
    Abstract [en]

    Swedish eScience Education (SeSE) is a national graduate school in eScience in Sweden. It comes from the collaboration between two major research initiatives in eScience and the school has turned out to be very successful. It has made it possible for students at different universities to get access to education that is not normally available at their home universities. With SeSE they get access to education by the top experts within their respective field. We argue why such graduate school is important and how it is different from training offered by many HPC centres in Europe. Furthermore, examples of courses and their structure is discussed as well as lessons learned from SeSE and its two predecessors in Sweden.

  • 13.
    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, 193002- p.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.

  • 14.
    Holmgren, Sverker
    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, Numerical Analysis.
    Peterson, Christer
    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.
    Karlsson, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
    Time-marching methods for the time-dependent Schrödinger equation2004In: Proc. Int. Conference on Computational and Mathematical Methods in Science and Engineering: CMMSE-2004, Uppsala, Sweden: Uppsala University , 2004, 53-56 p.Conference paper (Other academic)
  • 15.
    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, 034307- p.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.

  • 16. Karlsson, H O
    Lanczos algorithms and cross correlation functions C-if(E)2003In: Journal of Theoretical and Computational Chemistry, ISSN 0219-6336, E-ISSN 1793-6888, Vol. 2, no 4, 523-535 p.Article in journal (Refereed)
    Abstract [en]

    Cross correlation (CC) functions C-if(E) play an important role in chemical physics. They appear in the description of reactive scattering, photo-dissociation, photo-electron spectroscopy and electron transfer to mention a few. In this paper, we discuss two methods based on the Lanczos algorithm to compute the CC function for several initial and final states at the same time, without diagonalization. The property of the coupled two-term recursions variant of the Lanczos algorithm that yields a decomposition T = U-k(T) Delta(k)U(k) of the tridiagonal Lanczos matrix is crucial. The first method, the quasi minimal-recursive residue generation method (QM-RRGM) is based on solving a set of linear equations whereas the second method is based on a band-Lanczos method. The computational cost is of the same order of magnitude for both methods and is given by the number of matrix-vector multiplications in the underlying Lanczos method. Only a small set of scalars needs to be updated each recursion. The methods are compared for a model problem, the continuum resonance Raman cross section for a collinear model of CH2IBr. Both methods shows similar convergence properties. By adding a pre-conditioner, the rate of convergence can be increased dramatically.

  • 17. Karlsson, H O
    et al.
    Bendazzoli, G L
    Goscinski, O
    Evangelisti, S
    Density of states of alternant cyclic polyenes (CH)(N) by a direct Lanczos method1997In: International Journal of Quantum Chemistry, ISSN 0020-7608, E-ISSN 1097-461X, Vol. 63, no 3, 719-728 p.Article in journal (Refereed)
    Abstract [en]

    A direct full configuration interaction approach, previously used for studying individual low-lying eigenvalues, is combined with iterative Lanczos calculations, in order to obtain global properties of large Hermitean Hamiltonian matrices. To this effect systematic generation of random start vectors is used to compute statistical approximations to the density of states (DOS). Applications for cyclic polyenes in order to illustrate the viability of the scheme modeled by correlated, tight-binding Pariser-Parr-Pople (PPP) Hamiltonians of increasing complexity are presented. The degree of correlation in the solutions is controlled by the parameter beta. Convergence properties of the DOS for N=10 and N=14 are studied varying the extent of correlation. (C) 1997 John Wiley & Sons, Inc.

  • 18. Karlsson, H O
    et al.
    Goscinski, O
    Correlation functions and thermal rate constants2001In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 105, no 12, 2599-2603 p.Article in journal (Refereed)
    Abstract [en]

    Thermal rate constants k(T) and cumulative reaction probabilities N(E) can be computed as a sum of correlation functions C-nm = <(n)/f((H) over tilde/phi (m)). In this paper we discuss the use of two different Krylov subspace methods to compute these correlation functions for large systems. The first approach is based on the Lanczos algorithm to transform the Hamiltonian to tridiagonal form. As shown by Mandelshtam (J. Chem, Phys. 1998, 108, 9999) and Chen and Guo (J, Chem. Phys. 1999, 111, 9944), ail correlation functions can be computed from a single recursion. The second approach treats a number of linear systems of equations using a Krylov subspace solver. Here the quasiminimal residual (QMR) method was used. For the first approach, we found that we needed the same number of Lanczos recursions as the size of the matrix. If Ilo re-orthogonalization is used, the number of recursions grows further. The linear solver approach, on the other hand, converges fast for each linear system, but many systems must be solved.

  • 19.
    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, 10263-10268 p.Article 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.

  • 20.
    Karlsson, Hans
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Quantum Chemistry.
    Goscinski, Osvaldo
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Quantum Chemistry.
    Correlation functions and thermal rate constants2001In: Journal of Physical Chemistry A, Vol. 105, no 12, 2599-2603 p.Article in journal (Refereed)
  • 21.
    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.))
  • 22.
    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, 205102- p.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.

  • 23.
    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, 9366-9371 p.Article 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.

  • 24.
    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, 084105- p.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.

  • 25.
    Karlsson, Hans O
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Dynamics of hydrogenic wave packets in electric and magnetic fields1994In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 50, no 5, 3787-3792 p.Article in journal (Refereed)
    Abstract [en]

    The survival probability P(t) of hydrogenic wave packets for some choices of strong external electric and magnetic fields is studied. The recursive residue generation method, in combination with complex dilation and a Laguerre basis, is used to calculate the local density of states from which P(t) is computed via a Fourier transform. P(t) is calculated both for a single initial ‖8p0〉 state and for an initial radial hydrogenic wave packet centered around n=15. In the first case only, in principle, a single n manifold is involved in the dynamics, while in the latter case several n manifolds contribute. The different choices of initial states lead to significantly different results. The choice of fields was made in order to exemplify various patterns of behavior. Results similar to those obtained here were found in recent experiments by Broers and co-workers [Phys. Rev. Lett. 71, 344 (1993); Phys. Rev. A 49, 2498 (1994)]. The results presented in this work are quantum-mechanical calculations of hydrogenic wave packets in strong fields that include the effect of finite lifetimes on P(t).

  • 26.
    Karlsson, Hans O
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Exterior complex dilation for grid methods: Application to the cumulative reaction probability1998In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 108, no 10, 3849-3853 p.Article in journal (Refereed)
    Abstract [en]

    Exterior complex dilation (ECD) is introduced for the discrete variable representation (DVR) via a general coordinate mapping. The procedure leads to a computationally efficient and easily implemented approach for imposing outgoing boundary conditions, comparable with absorbing potentials in terms of minimizing the grid and parameters used. ECD relies on a rigorous mathematical framework in contrast to absorbing potentials. The DVR-ECD approach is illustrated by computation of the cumulative reaction probability for the H+H-2 reaction in one and two dimensions.

  • 27.
    Karlsson, Hans O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Lanczos algorithms and cross correlation functions2003In: Journal of Theoretical and Computatational Chemistry, Vol. 2, no 4, 523- p.Article in journal (Refereed)
  • 28.
    Karlsson, Hans O
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Predissociation resonances in CO and IBr: Smooth exterior scaling combined with the discrete variable representation2000In: European Physical Journal D: Atomic, Molecular and Optical Physics, ISSN 1434-6060, E-ISSN 1434-6079, Vol. 11, no 2, 207-212 p.Article in journal (Refereed)
    Abstract [en]

    Smooth exterior scaling (SES) and the discrete variable representation (DVR) are combined to accurately compute predissociation resonances of a bound state non-adiabatically coupled to a dissociative state. For the CO(B(1)Sigma(+)-D('1)Sigma(+)) predissociation interaction good agreement is found with approaches based on optical potentials and complex scaling. The comparison is done both in the diabatic and the adiabatic representation. The effect of the coupling strength in the IBr (B(3)Pi(0+)-Y0(+)) predissociation interaction and the transition from the diabatic to the adiabatic picture was studied by computing resonances for coupling strengths from 50 cm(-1) up to 300 cm(-1). The transition from weak (diabatic) to strong (adiabatic) coupling was clearly seen. The intermediate case leads to a complicated resonance distribution. Comparison was made with recent studies using pump-probe spectroscopy [M. Shapiro, M.J.J. Vrakking, A. Stolow, J. Chem. Phys. 110, 2465 (1999)]. It was found that the overall features of the experiment could be explained from the resonance distribution, but for a detailed comparison more accurate potential energy surfaces and couplings are needed.

  • 29.
    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, 125205- p.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.

  • 30.
    Karlsson, Hans O
    Department of Chemistry, University of California, Berkeley, California .
    The quasi‐minimal residual algorithm applied to complex symmetric linear systems in quantum reactive scattering1995In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 103, no 12, 4914-4919 p.Article in journal (Refereed)
    Abstract [en]

    The solution of systems of linear equations Ax=b with complex symmetric coefficient matrix A of size N, typically appearing in quantum-reactive scattering problems, is discussed. The quasiminimal residual (QMR) method is introduced to solve the complex symmetric linear system and is compared to the generalized minimal residual (GMRES) method. The methods are applied to two different chemical problems: the initial state-selected reaction probability for the H-2+OH-->H +H2O reaction, and the cumulative reaction probability for the isomerization of ketene, both with N>10(4). It is shown that the QMR method behaves more favorably, i.e., converges faster, than the GMRES for large N, especially when high accuracy is needed

  • 31.
    Karlsson, Hans O
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Bendazzoli, GL
    Goscinski, Osvaldo
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Evangelisti, S
    Density of states of alternant cyclic polyenes (CH)(N) by a direct Lanczos method1997In: International Journal of Quantum Chemistry, ISSN 0020-7608, E-ISSN 1097-461X, Vol. 63, no 3, 719-728 p.Article in journal (Other academic)
    Abstract [en]

    A direct full configuration interaction approach, previously used for studying individual low-lying eigenvalues, is combined with iterative Lanczos calculations, in order to obtain global properties of large Hermitean Hamiltonian matrices. To this effect systematic generation of random start vectors is used to compute statistical approximations to the density of states (DOS). Applications for cyclic polyenes in order to illustrate the viability of the scheme modeled by correlated, tight-binding Pariser-Parr-Pople (PPP) Hamiltonians of increasing complexity are presented. The degree of correlation in the solutions is controlled by the parameter beta. Convergence properties of the DOS for N=10 and N=14 are studied varying the extent of correlation.

  • 32.
    Karlsson, Hans O
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Goscinski, Osvaldo
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    A direct recursive residue generation method: application to photoionization of hydrogen in static electric fields1994In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 27, no 6, 1061-1072 p.Article in journal (Refereed)
    Abstract [en]

    In studies of hydrogenic systems via the recursive residue generation method (RRGM) the major bottleneck is the matrix vector product HC, between the Hamiltonian matrix H and a Lanczos vector C. For highly excited states and/or strong perturbations the size of H grows fast leading to storage problems. By making-use of direct methods, i.e. avoidance of explicit construction on of large Hamiltonian matrices, such problems can be overcome. Utilizing the underlying analytical properties of the Laguerre basis e(-lambdar)L(k)2I+2(2lambdar) a direct RRGM (D-RRGM) for the unperturbed hydrogenic Hamiltonian is derived, changing the storage needs from scaling as N2 to 4N where N is the number of radial functions for each factorized H-0(l, m) block with the possibility of parallel processing. A further computational simplification is introduced by putting the expression for the photoionization (PI) cross section in the rational form conventionally used in the representation of density or states (DOS). This allows the construction of the PI cross section directly from the tridiagonal Lanczos matrix avoiding the explicit calculation of individual eigenvalues and eigenvectors. To illustrate and verify the method the PI cross section for a hydrogen atom in a static electric field, for both pi and cr polarization, was calculated for an electric field strength of F = 5714 V cm-1. Sufficiently large basis sets could be employed so that good comparison with experiment and other theoretical work was obtained, including the field-induced modulations near the zero-field ionization limit.

  • 33.
    Karlsson, Hans O
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Goscinski, Osvaldo
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Perturbed hydrogenic manifolds studied by the recursive residue generation method1992In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 25, no 23, 5015-5028 p.Article in journal (Refereed)
    Abstract [en]

    A method for calculating the perturbation of hydrogenic manifolds, the emerging bound states and resonances, for arbitrary combinations of external fields, is presented. It requires the combined use of complex dilation, an orthonormal Laguerre basis e(-lambdar) L(k)2l+2 (lambdar) rather than the non-orthogonal Sturmians e(-lambdar) L(k)2l+1 (lambdar), and the recursive residue generation method (RRGM) version of the Lanczos algorithm. Generalized eigenvalue problems are avoided. Furthermore, direct computation of the residues of resolvents, transition amplitudes and sum rules is achieved, Comparison with other methods and with previous calculations, suitable for one perturbation at a time, indicates that high accuracy is achieved separately both for the 1s Stark resonance and for the 1s Zeeman effect. Accurate results for the 1s Stark-Zeeman resonance, for various combinations of fields, are given.

  • 34.
    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, 9116-9123 p.Article in journal (Refereed)
  • 35.
    Karlsson, Hans O
    et al.
    Department of Chemistry, University of California, Berkeley,USA.
    Thompson, Ward H
    Department of Chemistry, University of California, Berkeley,USA.
    Miller, William H
    Department of Chemistry, University of California, Berkeley, USA.
    Theoretical calculation of photodetachment intensities for H3O-1996In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 105, no 13, 5387-5396 p.Article in journal (Refereed)
    Abstract [en]

    We have calculated total and arrangement-selected photodetachment intensities for the H3O- anion (and its deuterated form, D3O-) using a Green's function in a discrete variable representation with absorbing boundary conditions. A multiply-shifted quasiminimal residual method is used to obtain the Green's function for many energies at once. We present spectra obtained by explicitly treating two and four degrees of freedom. Comparison with experiment indicates that the bending angles in the anion and neutral are more similar than in the current potential energy surfaces. The calculated spectra are also consistent with the suggestion that the barrier should be ''earlier.'

  • 36. KARLSSON, HO
    THE QUASI-MINIMAL RESIDUAL ALGORITHM APPLIED TO COMPLEX SYMMETRICAL LINEAR-SYSTEMS IN QUANTUM REACTIVE SCATTERING1995In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 103, no 12, 4914-4919 p.Article in journal (Refereed)
    Abstract [en]

    The solution of systems of linear equations Ax=b with complex symmetric coefficient matrix A of size N, typically appearing in quantum-reactive scattering problems, is discussed. The quasiminimal residual (QMR) method is introduced to solve the complex symmetric linear system and is compared to the generalized minimal residual (GMRES) method. The methods are applied to two different chemical problems: the initial state-selected reaction probability for the H-2+OH-->H +H2O reaction, and the cumulative reaction probability for the isomerization of ketene, both with N>10(4). It is shown that the QMR method behaves more favorably, i.e., converges faster, than the GMRES for large N, especially when high accuracy is needed. (C) 1995 American Institute of Physics.

  • 37. KARLSSON, HO
    et al.
    GOSCINSKI, O
    A DIRECT RECURSIVE RESIDUE GENERATION METHOD - APPLICATION TO PHOTOIONIZATION OF HYDROGEN IN STATIC ELECTRIC-FIELDS1994In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 27, no 6, 1061-1072 p.Article in journal (Refereed)
    Abstract [en]

    In studies of hydrogenic systems via the recursive residue generation method (RRGM) the major bottleneck is the matrix vector product HC, between the Hamiltonian matrix H and a Lanczos vector C. For highly excited states and/or strong perturbations the size of H grows fast leading to storage problems. By making-use of direct methods, i.e. avoidance of explicit construction on of large Hamiltonian matrices, such problems can be overcome. Utilizing the underlying analytical properties of the Laguerre basis e(-lambdar)L(k)2I+2(2lambdar) a direct RRGM (D-RRGM) for the unperturbed hydrogenic Hamiltonian is derived, changing the storage needs from scaling as N2 to 4N where N is the number of radial functions for each factorized H-0(l, m) block with the possibility of parallel processing. A further computational simplification is introduced by putting the expression for the photoionization (PI) cross section in the rational form conventionally used in the representation of density or states (DOS). This allows the construction of the PI cross section directly from the tridiagonal Lanczos matrix avoiding the explicit calculation of individual eigenvalues and eigenvectors. To illustrate and verify the method the PI cross section for a hydrogen atom in a static electric field, for both pi and cr polarization, was calculated for an electric field strength of F = 5714 V cm-1. Sufficiently large basis sets could be employed so that good comparison with experiment and other theoretical work was obtained, including the field-induced modulations near the zero-field ionization limit.

  • 38. KARLSSON, HO
    et al.
    GOSCINSKI, O
    PERTURBED HYDROGENIC MANIFOLDS STUDIED BY THE RECURSIVE RESIDUE GENERATION METHOD1992In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 25, no 23, 5015-5028 p.Article in journal (Refereed)
    Abstract [en]

    A method for calculating the perturbation of hydrogenic manifolds, the emerging bound states and resonances, for arbitrary combinations of external fields, is presented. It requires the combined use of complex dilation, an orthonormal Laguerre basis e(-lambdar) L(k)2l+2 (lambdar) rather than the non-orthogonal Sturmians e(-lambdar) L(k)2l+1 (lambdar), and the recursive residue generation method (RRGM) version of the Lanczos algorithm. Generalized eigenvalue problems are avoided. Furthermore, direct computation of the residues of resolvents, transition amplitudes and sum rules is achieved, Comparison with other methods and with previous calculations, suitable for one perturbation at a time, indicates that high accuracy is achieved separately both for the 1s Stark resonance and for the 1s Zeeman effect. Accurate results for the 1s Stark-Zeeman resonance, for various combinations of fields, are given.

  • 39.
    Kieri, Emil
    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 Chemistry - Ångström, Theoretical Chemistry.
    An adaptive pseudospectral method for wave packet dynamics2012In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 137, 044111:1-12 p.Article in journal (Refereed)
  • 40. 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, 033431- p.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.

  • 41.
    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, 491-506 p.Article in journal (Refereed)
  • 42.
    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)
  • 43.
    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, 184101:1-11 p.Article in journal (Refereed)
  • 44.
    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)
  • 45.
    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 Hamiltonian2011In: Journal of Computational Science, ISSN 1877-7503, E-ISSN 1877-7511, Vol. 2, 178-187 p.Article in journal (Refereed)
  • 46.
    Leitner, Torsten
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Buchner, Franziska
    Rouzee, Arnaud
    Rading, Linea
    Johnsson, Per
    Odelius, Michael
    Karlsson, Hans O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Vrakking, Marc
    Wernet, Philippe
    Coherent wave packet dynamics in photo-excited Nal2013In: EPJ Web of Conferences, ISSN 2101-6275, E-ISSN 2100-014X, Vol. 41, 02027- p.Article in journal (Other academic)
    Abstract [en]

    Time and energy resolved photoelectron distributions of photo-excited Nal are presented. A splitting in the photo-excited state suggested by calculations of the intramolecular potential energy surfaces could be confirmed experimentally for the first time.

  • 47. Liu, Y J
    et al.
    Persson, P
    Karlsson, H O
    Lunell, S
    Kadi, M
    Karlsson, D
    Davidsson, J
    Photodissociation of bromobenzene, dibromobenzene, and 1,3,5-tribromobenzene2004In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 120, no 14, 6502-6509 p.Article in journal (Refereed)
    Abstract [en]

    Quantum chemical calculations have been performed on the ground state and several low-lying excited states of bromobenzene, ortho-, meta-, and para-dibromobenzene, and 1,3,5-tribromobenzene using high-level ab initio and hybrid density-functional methods. Experimental observations of ultrafast predissociation in these molecules are clarified from extensive theoretical information about all low-energy potential-energy curves together with symmetry arguments. The intriguing observation that o- and m-dibromobenzene have two ultrafast predissociation channels while bromobenzene, p-dibromobenzene, and 1,3,5-tribromobenzene only have one such channel is explained from the calculated potential-energy curves. These show that the lowering of point-group symmetry from C-2v to C-s along the main photodissociation reaction coordinate, which only occurs in o- and m-dibromobenzene, opens up a new predissociation channel. Dynamical quantum simulations based on the calculated potential-energy curves are used to estimate the coupling strength at the intersystem crossing point in bromobenzene. (C) 2004 American Institute of Physics.

  • 48.
    Liu, Ya-Jun
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Persson, Petter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Karlsson, Hans O.
    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.
    Kadi, Malin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Karlsson, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Davidsson, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Photodissociation of Bromobenzene, Dibromobenzene, and 1,3,5-Tribromobenzene2004In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 120, no 14, 6502- p.Article in journal (Refereed)
    Abstract [en]

    Quantum chemical calculations have been performed on the ground state and several low-lying excited states of bromobenzene, ortho-, meta-, and para-dibromobenzene, and 1,3,5-tribromobenzene using high-level ab initio and hybrid density-functional methods. Experimental observations of ultrafast predissociation in these molecules are clarified from extensive theoretical information about all low-energy potential-energy curves together with symmetry arguments. The intriguing observation that o- and m-dibromobenzene have two ultrafast predissociation channels while bromobenzene, p-dibromobenzene, and 1,3,5-tribromobenzene only have one such channel is explained from the calculated potential-energy curves. These show that the lowering of point-group symmetry from C2v to Cs along the main photodissociation reaction coordinate, which only occurs in o- and m-dibromobenzene, opens up a new predissociation channel. Dynamical quantum simulations based on the calculated potential-energy curves are used to estimate the coupling strength at the intersystem crossing point in bromobenzene.

  • 49.
    Nissen, Anna
    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, Numerical Analysis.
    Karlsson, Hans O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Kreiss, Gunilla
    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.
    A perfectly matched layer applied to a reactive scattering problem2010In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 133, 054306:1-11 p.Article in journal (Refereed)
  • 50. Petersson, A
    et al.
    Ratner, M
    Karlsson, H O
    Injection time in the metaloxide-molecule interface calculated within the tight-binding model2000In: JOURNAL OF PHYSICAL CHEMISTRY B, ISSN 1089-5647, Vol. 104, no 35, 8498-8502 p.Article in journal (Refereed)
    Abstract [en]

    The injection time tau of the electron transfer from an excited electronic state of a dye molecule to a semiconducting surface is studied, An analytical expression for the injection time as a function of excitation energy is derived. The semiconductor is described as a one-dimensional chain in the tight-binding approximation, and the dye molecule is included via the coupling to the semiconductor. For a TiO2 semiconductor the injection time is estimated to be approximately 5 fs. The results support and characterize recent experimental studies.

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