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  • 1. Bernigaud, Virgile
    et al.
    Cederquist, Henrik
    Stockholm University, Faculty of Science, Department of Physics.
    Haag, Nicole
    Stockholm University, Faculty of Science, Department of Physics.
    Holm, Anne I. S.
    Stockholm University, Faculty of Science, Department of Physics.
    Huber, Bernd A.
    Hvelplund, Preben
    Kadhane, Umesh
    Larsen, Mikkel Koefod
    Manil, Bruno
    Nielsen, Steen Bröndsted
    Panja, Subhasis
    Ptasinska, Sylwia
    Rangama, Jimmy
    Reinhed, Peter
    Stockholm University, Faculty of Science, Department of Physics.
    Schmidt, Henning T.
    Stockholm University, Faculty of Science, Department of Physics.
    Streletskii, Alexey V.
    Stöchkel, Kristian
    Worm, Esben S.
    Zettergren, Henning
    Stockholm University, Faculty of Science, Department of Physics.
    Electron capture-induced dissociation of AK dipeptide dications: Influence of ion velocity, crown-ether complexation and collision gas2008In: International Journal of Mass Spectrometry, ISSN 1387-3806, E-ISSN 1873-2798, Vol. 276, no 2-3, p. 77-81Article in journal (Refereed)
    Abstract [en]

    The fragmentation of doubly protonated AK dipeptide ions has been investigated after collisional electron transfer. Electron capture leads to three dominant channels, H loss, NH3 loss, and N–Cα bond breakage to give either c+ or z+ fragment ions. The relative importance of these channels has been explored as a function of ion velocity, the degree of complexation with crown ether, and collision gas. Our results indicate that H loss and NH3 loss are competing channels whereas the probability of N–Cα bond breakage is more or less constant.

  • 2.
    Danielsson, Mathias
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Simonsson, Ansgar
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Paál, Andreas
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitaly
    Stockholm University, Faculty of Science, Department of Physics.
    Ehlerding, Anneli
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, Magdalena
    Stockholm University, Faculty of Science, Department of Physics.
    Hellberg, Fredrik
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard
    Stockholm University, Faculty of Science, Department of Physics.
    Österdal, Fabian
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Källberg, Anders
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    The cross-section and branching fractions for dissociative recombination of the diacetylene cation C4D2+2008In: International Journal of Mass Spectrometry, ISSN 1387-3806, E-ISSN 1873-2798, Vol. 273, no 3, p. 111-116Article in journal (Refereed)
    Abstract [en]

    In this paper we report the results of a study on the dissociative recombination (DR) of the diacetylene cation, C4D2+, which has been carried out at the ion storage ring CRYRING in Stockholm, Sweden. The energy-dependent absolute DR cross-section as well as the branching fractions at 0 eV collision energy were measured. The DR cross-section was best fitted using the expression σ(E) = (7.5 ± 1.5) × 10−16 × E−(1.29±0.03) cm2 over the collision energy range 1–100 meV. The thermal rate coefficient was deduced from the cross-section to be α(T) = (1.10 ± 0.15) × 10−6 × (T/300)−(0.79±0.03) cm3/s. The reported branching fractions for C4D2+ agree with previous experiments on the DR of C4H2+ performed at the ASTRID storage ring in Aarhus, Denmark, and furthermore, indicate that the DR of C4D2+ possesses only two channels leading to the following products: C4D + D (75%) and C2D + C2D (25%).

  • 3.
    Fathi, Pantea
    Stockholm University, Faculty of Science, Department of Physics.
    Insights on molecular growth pathways in Titan’s ionosphere through combined experimental and theoretical studies of the C2H2N+ + C2H4 ion-neutral reactionIn: International Journal of Mass Spectrometry, ISSN 1387-3806, E-ISSN 1873-2798Article in journal (Refereed)
    Abstract [en]

    The gas phase reactivity of C2H2N+ with C2H4 is studied using a combined experimental and theoretical approach through guided ion beam mass spectrometry (GIB-MS) and ab initio calculations. Results indicate the formation of C3H5+, C2H4+, C4H5N+ and C3H3+ as major products, in addition to minor generation of C2H3+, C2H4N+, C4H4N+, C3H2N+, and CH3+. Theoretical calculations show that reaction proceeds via formation and subsequent rearrangements of a [C4H6N]+ adduct. In the quest to probe its singlet electronic state hypersurface, the most relevant stationary points along the reaction pathway leading to the various products are located and optimized. The results of our calculations at the MP2/6-311++G(d,p) level were found to be in agreement with our experimental findings, as well as with the derived enthalpies of reaction for the designated reaction channels. The present study provides substantial new insights on the formation of complex organics in Titan’s ionosphere detected by the Ion and Neutral Mass Spectrometer (INMS) onboard the Cassini spacecraft. These pathways might also be of relevance for the generation of long chain carbon-nitrogen bearing compounds in low-temperature environments e.g. the interstellar medium or circumstellar envelopes.

  • 4.
    Fathi, Pantea
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Ascenzi, D.
    Experimental and theoretical investigations of the ion-neutral reaction of C2H2N+ with C2H6 and implications on chain elongation processes in Titan's atmosphere2016In: International Journal of Mass Spectrometry, ISSN 1387-3806, E-ISSN 1873-2798, Vol. 411, p. 1-13Article in journal (Refereed)
    Abstract [en]

    In this study we report theoretical and experimental evidence for the formation of ionic products by the ion-neutral reaction of C2H2N+ with C2H6. Our investigations consist of laboratory measurements using a guided ion beam mass spectrometer together with complementary ab initio quantum chemical computations, at the MP2/6-311++G(d,p) level of theory, in order to elucidate the energetics and geometries of the intermediates and transition states that are involved in the production of the observed product ions. This study also provides insights on the isomeric nature of the observed product ions, their formation pathways together with collision energy and pressure dependences. The experimental data agrees well with the predictions of the ab initio calculations. Despite data provides evidence for the occurrence of C2H5+ as the most salient product ion, the production of CH3+, C2H3+, C3H5+, C3H7+ and C2H4N+ is also evident. A reaction scheme was proposed to elucidate the mechanisms responsible for the formation of the observed product ions. These processes might be intermediate steps in the generation of long chain carbon and nitrogen-bearing compounds in Titan's ionosphere, the interstellar medium or circumstellar envelopes.

  • 5.
    Fritioff, Tomas
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Bergström, Ingmar
    Nagy, Sz
    Stockholm University, Faculty of Science, Department of Physics.
    Solders, Andreas
    Stockholm University, Faculty of Science, Department of Physics.
    Suhonen, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Schuch, Reinhold
    Stockholm University, Faculty of Science, Department of Physics.
    Precise measurements of ionic masses for QED tests2006In: International Journal of Mass Spectrometry, ISSN 1387-3806, E-ISSN 1873-2798, Vol. 251, no 2-3, p. 281-285Article in journal (Refereed)
    Abstract [en]

    The Penning trap mass spectrometer SMILETRAP is designed for precision mass measurements using the merits of highly charged ions. In this paper we describe the feature of SMILETRAP and give examples of mass measurements involving , , and ions. These emphasize the importance of accurate masses of hydrogen-like and lithium-like ions that are required in the evaluation of g-factor measurements of electrons bound to even–even nuclei and test of QED effects. Highly precise mass measurements can also be used for testing atomic structure calculations and determining atomic binding energies. Relevance of such measurements throughout the periodic system is discussed.

  • 6.
    Gatchell, Michael
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Stockett, Mark
    Stockholm University, Faculty of Science, Department of Physics.
    Rousseau, P.
    Chen, Tao
    Stockholm University, Faculty of Science, Department of Physics.
    Kulyk, Kostiantyn
    Stockholm University, Faculty of Science, Department of Physics.
    Schmidt, Henning
    Stockholm University, Faculty of Science, Department of Physics.
    Chesnel, J. Y.
    Domaracka, A.
    Méry, A.
    Maclot, S.
    Adoui, L.
    Stöchkel, K.
    Hvelplund, P.
    Wang, Y.
    Alcamí, M.
    Huber, B. A.
    Martín, F.
    Zettergren, Henning
    Stockholm University, Faculty of Science, Department of Physics.
    Cederquist, Henrik
    Stockholm University, Faculty of Science, Department of Physics.
    Non-statistical fragmentation of PAHs and fullerenes in collisions with atoms2014In: International Journal of Mass Spectrometry, ISSN 1387-3806, E-ISSN 1873-2798, Vol. 365, p. 260-265Article in journal (Refereed)
    Abstract [en]

    Non-statistical fragmentation processes may be important when Polycyclic Aromatic Hydrocarbon molecules (PAHs), fullerenes, or other large complex molecules collide with atoms and atomic ions. For collisions with hydrogen or helium this occurs for center-of-mass energies between a few tens to a few hundreds of electron volts and typically results in losses of single atoms. In such processes one forms much more reactive fragments than in statistical fragmentation, which instead are dominated by losses of C2- or C2H2-molecules (H-atoms) from fullerenes and PAHs, respectively. An enhanced reactivity has recently been demonstrated for van der Waals clusters of C60 molecules where prompt knockouts of single C-atoms from one of the fullerenes yield highly reactive C59+ fragments, which easily form covalent bonds with a C60 molecule inside the clusters

  • 7.
    Kulyk, Kostiantyn
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Rebrov, Oleksii
    Stockholm University, Faculty of Science, Department of Physics.
    Stockett, Mark H.
    Stockholm University, Faculty of Science, Department of Physics.
    Alexander, John D.
    Stockholm University, Faculty of Science, Department of Physics.
    Zettergren, Henning
    Stockholm University, Faculty of Science, Department of Physics.
    Schmidt, Henning T.
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Cederquist, Henrik
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    High-energy collisions of protonated enantiopure amino acids with a chiral target gas2015In: International Journal of Mass Spectrometry, ISSN 1387-3806, E-ISSN 1873-2798, Vol. 388, p. 59-64Article in journal (Refereed)
    Abstract [en]

    We have studied the fragmentation of the singly protonated L- and D-forms of enantiomerically pure phenylalanine (Phe), tryptophan (Trp), and methionine (Met) in high-energy collisions with chiral and achiral gas targets. (S)-(+)-2-butanol, racemic (+/-)-2-butanol, and argon were used as target gases. At center-of-mass frame collision energy of I key, it was found that all of the ions exhibit common fragmentation pathways which are independent of target chirality. For all projectile ions, the elimination of NH3 and H2O + CO were found to be the main reaction channels. The observed fragmentation patterns were dominated by statistically driven processes. The energy deposited into the ions was found to be sufficient to yield multiple fragment ions, which arise from decomposition via various competitive reaction pathways.

  • 8.
    Stockett, Mark H.
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Aarhus University, Denmark.
    Gatchell, Michael
    Stockholm University, Faculty of Science, Department of Physics.
    de Ruette, Nathalie
    Stockholm University, Faculty of Science, Department of Physics.
    Giacomozzi, Linda
    Stockholm University, Faculty of Science, Department of Physics.
    Chen, Tao
    Stockholm University, Faculty of Science, Department of Physics.
    Rousseau, P.
    Maclot, S.
    Chesnel, J. -Y.
    Adoui, L.
    Huber, B. A.
    Berzins, U.
    Schmidt, Henning T.
    Stockholm University, Faculty of Science, Department of Physics.
    Zettergren, Henning
    Stockholm University, Faculty of Science, Department of Physics.
    Cederquist, Henrik
    Stockholm University, Faculty of Science, Department of Physics.
    Isomer effects in fragmentation of Polycyclic Aromatic Hydrocarbons2015In: International Journal of Mass Spectrometry, ISSN 1387-3806, E-ISSN 1873-2798, Vol. 392, p. 58-62Article in journal (Refereed)
    Abstract [en]

    We have observed significant differences in the fragmentation patterns of isomeric Polycyclic Aromatic Hydrocarbon (PAH) cations following collisions with helium atoms at center-of-mass energies around 100 eV. This is in contrast to the situation at other collision energies or in photo-absorption experiments where isomeric effects are very weak and where the lowest-energy dissociation channels (H- and C2H2-loss) domihate in statistical fragmentation processes. In the 100 eV range, non-statistical fragmentation also competes and is uniquely linked to losses of single carbon atoms (CHx-losses). We find that such CHx-losses are correlated with the ionic ground state energy within a given group of isomers. We present results for three C16H10+, four C18H12+ and five C20H12+ isomers colliding with He.

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