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Publications (10 of 59) Show all publications
Vacher, M., Brakestad, A., Karlsson, H. O., Fernández Galván, I. & Lindh, R. (2017). Dynamical Insights into the Decomposition of 1,2-Dioxetane. Journal of Chemical Theory and Computation, 13(6), 2448-2457
Open this publication in new window or tab >>Dynamical Insights into the Decomposition of 1,2-Dioxetane
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2017 (English)In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 13, no 6, p. 2448-2457Article in journal (Refereed) Published
Abstract [en]

Chemiluminescence in 1,2-dioxetane occurs through a thermally activated decomposition reaction into two formaldehyde molecules. Both ground-state and nonadiabatic dynamics (including singlet excited states) of the decomposition reaction have been simulated, starting from the first O–O bond-breaking transition structure. The ground-state dissociation occurs between t = 30 fs and t = 140 fs. The so-called entropic trap leads to frustrated dissociations, postponing the decomposition reaction. Specific geometrical conditions are necessary for the trajectories to escape from the entropic trap and for dissociation to be possible. The singlet excited states participate as well in the trapping of the molecule: dissociation including the nonadiabatic transitions to singlet excited states now occurs from t = 30 fs to t = 250 fs and later. Specific regions of the seam of the So/S1 conical intersections that would "retain" the molecule for longer on the excited state have been identified.

National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-329717 (URN)10.1021/acs.jctc.7b00198 (DOI)000403530100009 ()28437611 (PubMedID)
Funder
Swedish Research Council, 2012-3910
Available from: 2017-10-02 Created: 2017-10-02 Last updated: 2017-10-02Bibliographically approved
Vacher, M., Farahani, P., Valentini, A., Frutos, L. M., Karlsson, H. O., Fernández Galván, I. & Lindh, R. (2017). How Do Methyl Groups Enhance the Triplet Chemiexcitation Yield of Dioxetane?. Journal of Physical Chemistry Letters, 8(16), 3790-3794
Open this publication in new window or tab >>How Do Methyl Groups Enhance the Triplet Chemiexcitation Yield of Dioxetane?
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2017 (English)In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 8, no 16, p. 3790-3794Article in journal (Refereed) Published
Abstract [en]

Chemiluminescence is the emission of light as a result of a nonadiabatic chemical reaction. The present work is concerned with understanding the yield of chemiluminescence, in particular how it dramatically increases upon methylation of 1,2-dioxetane. Both ground-state and nonadiabatic dynamics (including singlet excited states) of the decomposition reaction of various methyl-substituted dioxetanes have been simulated. Methyl-substitution leads to a significant increase in the dissociation time scale. The rotation around the O-C-C-O dihedral angle is slowed; thus, the molecular system stays longer in the "entropic trap" region. A simple kinetic model is proposed to explain how this leads to a higher chemiluminescence yield. These results have important implications for the design of efficient chemiluminescent systems in medical, environmental, and industrial applications.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2017
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-334304 (URN)10.1021/acs.jpclett.7b01668 (DOI)000408187400012 ()28749694 (PubMedID)
Funder
Swedish Research Council, 2016-03398
Available from: 2017-11-23 Created: 2017-11-23 Last updated: 2017-11-23Bibliographically approved
Hast, A., Hanke, M. & Karlsson, H. O. (2015). Swedish eScience Education – a Graduate School in eScience. In: Proc. 11th International Conference on e-Science: . Paper presented at e-Science 2015, August 31–September 4, Munich, Germany (pp. 31-35). IEEE Computer Society
Open this publication in new window or tab >>Swedish eScience Education – a Graduate School in eScience
2015 (English)In: Proc. 11th International Conference on e-Science, IEEE Computer Society, 2015, p. 31-35Conference paper, Published 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.

Place, publisher, year, edition, pages
IEEE Computer Society, 2015
Keyword
Graduate Education; eScience; Training; Sweden; High Performance Computing
National Category
Other Computer and Information Science
Identifiers
urn:nbn:se:uu:diva-266132 (URN)10.1109/eScience.2015.19 (DOI)000380433500004 ()9781467393256 (ISBN)
External cooperation:
Conference
e-Science 2015, August 31–September 4, Munich, Germany
Projects
eSSENCE
Available from: 2015-09-04 Created: 2015-11-05 Last updated: 2018-01-10Bibliographically approved
Stegeby, H., Kowalewski, M., Piszczatowski, K. & Karlsson, H. O. (2015). Wave packet simulations of antiproton scattering on molecular hydrogen. Journal of Physics B: Atomic, Molecular and Optical Physics, 48(19), 195204:1-7, Article ID 195204.
Open this publication in new window or tab >>Wave packet simulations of antiproton scattering on molecular hydrogen
2015 (English)In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 48, no 19, p. 195204:1-7, article id 195204Article in journal (Refereed) Published
National Category
Theoretical Chemistry Computational Mathematics
Identifiers
urn:nbn:se:uu:diva-261547 (URN)10.1088/0953-4075/48/19/195204 (DOI)000361036700011 ()
Projects
eSSENCE
Available from: 2015-08-28 Created: 2015-09-01 Last updated: 2018-04-22Bibliographically approved
Fernández Galván, I., Karlsson, H., Stenrup, M. & Lindh, R. (2014). Quantum dynamics simulations of model chemiluminescence systems. Luminescence (Chichester, England Print), 29(S1), 67-67
Open this publication in new window or tab >>Quantum dynamics simulations of model chemiluminescence systems
2014 (English)In: Luminescence (Chichester, England Print), ISSN 1522-7235, E-ISSN 1522-7243, Vol. 29, no S1, p. 67-67Article in journal, Meeting abstract (Other academic) Published
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-228878 (URN)10.1002/bio.2699_3 (DOI)000337617800107 ()
Available from: 2014-06-10 Created: 2014-07-22 Last updated: 2017-12-05Bibliographically approved
Farahani, P., Lundberg, M. & Karlsson, H. O. (2013). Ab initio quantum mechanical calculation of the reaction probability for the Cl- + PH2Cl -> ClPH2 + Cl- reaction. Chemical Physics, 425, 134-140
Open this publication in new window or tab >>Ab initio quantum mechanical calculation of the reaction probability for the Cl- + PH2Cl -> ClPH2 + Cl- reaction
2013 (English)In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 425, p. 134-140Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2013
Keyword
Nucleophilic substitution (S(N)2); Reaction probability; Quantum dynamics
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-210368 (URN)10.1016/j.chemphys.2013.08.011 (DOI)000327443700016 ()
Funder
Marcus and Amalia Wallenberg FoundationSwedish National Infrastructure for Computing (SNIC), p2011004
Available from: 2013-11-06 Created: 2013-11-06 Last updated: 2017-12-06Bibliographically approved
Leitner, T., Buchner, F., Rouzee, A., Rading, L., Johnsson, P., Odelius, M., . . . Wernet, P. (2013). Coherent wave packet dynamics in photo-excited Nal. Paper presented at XVIIIth International Conference on Ultrafast Phenomena; 8 - 13 July 2012, Lausanne, Switzerland. EPJ Web of Conferences, 41, 02027
Open this publication in new window or tab >>Coherent wave packet dynamics in photo-excited Nal
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2013 (English)In: EPJ Web of Conferences, ISSN 2101-6275, E-ISSN 2100-014X, Vol. 41, p. 02027-Article in journal (Other academic) Published
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.

Place, publisher, year, edition, pages
EDP Sciences, 2013
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-218365 (URN)10.1051/epjconf/20134102027 (DOI)978-2-7598-0956-1 (ISBN)
Conference
XVIIIth International Conference on Ultrafast Phenomena; 8 - 13 July 2012, Lausanne, Switzerland
Available from: 2014-02-11 Created: 2014-02-11 Last updated: 2017-12-06Bibliographically approved
Kieri, E., Holmgren, S. & Karlsson, H. O. (2012). An adaptive pseudospectral method for wave packet dynamics. Journal of Chemical Physics, 137, 044111:1-12
Open this publication in new window or tab >>An adaptive pseudospectral method for wave packet dynamics
2012 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 137, p. 044111:1-12Article in journal (Refereed) Published
National Category
Computational Mathematics
Identifiers
urn:nbn:se:uu:diva-179058 (URN)10.1063/1.4737893 (DOI)000307611500012 ()
Projects
eSSENCE
Available from: 2012-07-26 Created: 2012-08-06 Last updated: 2017-12-07Bibliographically approved
Stegeby, H., Piszczatowski, K., Karlsson, H. O., Lindh, R. & Froelich, P. (2012). Variational calculations for the hydrogen-antihydrogen system with a mass-scaled Born-Oppenheimer potential. CENTRAL EUROPEAN JOURNAL OF PHYSICS, 10(5), 1038-1053
Open this publication in new window or tab >>Variational calculations for the hydrogen-antihydrogen system with a mass-scaled Born-Oppenheimer potential
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2012 (English)In: CENTRAL EUROPEAN JOURNAL OF PHYSICS, ISSN 1895-1082, Vol. 10, no 5, p. 1038-1053Article in journal (Refereed) Published
Abstract [en]

The problem of proton-antiproton motion in the H- system is investigated by means of the variational method. We introduce a modified nuclear interaction through mass-scaling of the Born-Oppenheimer potential. This improved treatment of the interaction includes the nondivergent part of the otherwise divergent adiabatic correction and shows the correct threshold behaviour. Using this potential we calculate the vibrational energy levels with angular momentum 0 and 1 and the corresponding nuclear wave functions, as well as the S-wave scattering length. We obtain a full set of all bound states together with a large number of discretized continuum states that might be utilized in variational four-body calculations. The results of our calculations gives an indication of resonance states in the hydrogen-antihydrogen system.

Keyword
antihydrogen; Born-Oppenheimer approximation; adiabatic approximation; matter-antimatter interactions
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-188930 (URN)10.2478/s11534-012-0131-y (DOI)000311496400002 ()
Available from: 2012-12-21 Created: 2012-12-21 Last updated: 2018-04-22Bibliographically approved
Karlsson, H. O. (2011). Accelerating the convergence of the Lanczos algorithm by the use of a complex symmetric Cholesky factorization: application to correlation functions in quantum molecular dynamics. Journal of Physics B: Atomic, Molecular and Optical Physics, 44(20), 205102
Open this publication in new window or tab >>Accelerating the convergence of the Lanczos algorithm by the use of a complex symmetric Cholesky factorization: application to correlation functions in quantum molecular dynamics
2011 (English)In: 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) Published
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.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-160714 (URN)10.1088/0953-4075/44/20/205102 (DOI)000295599500007 ()
Available from: 2011-11-02 Created: 2011-10-31 Last updated: 2017-12-08Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5366-4949

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