| 1. |
- Al-Khalili, A, et al.
(författare)
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Dissociative recombination cross section and branching ratios of protonated dimethyl disulfide and N-methylacetamide
- 2004
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 121:12, s. 5700-5708
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Tidskriftsartikel (refereegranskat)abstract
- Dimethyl disulfide (DMDS) and N-methylacetamide are two first choice model systems that represent the disulfide bridge bonding and the peptide bonding in proteins. These molecules are therefore suitable for investigation of the mechanisms involved when proteins fragment under electron capture dissociation (ECD). The dissociative recombination cross sections for both protonated DMDS and protonated N-methylacetamide were determined at electron energies ranging from 0.001 to 0.3 eV. Also, the branching ratios at 0 eV center-of-mass collision energy were determined. The present results give support for the indirect mechanism of ECD, where free hydrogen atoms produced in the initial fragmentation step induce further decomposition. We suggest that both indirect and direct dissociations play a role in ECD.
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| 2. |
- Fritioff, Karin, et al.
(författare)
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Observation of an excited C2-4 ion
- 2004
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 37:11, s. 2241-2246
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports an experimental investigation of the electron impact detachment of C−4. We observe structure in the electron impact cross section for detaching a single electron from a C−4 cluster anion, which we attribute to the formation and decay of the C2−4 dianion. The system is energetically unstable and very rapidly decays via double autodetachment. The energy and width of the resonance were determined to be 8.8(5) eV and 1.4(5) eV, respectively, and the resonance lies 1.5(5) eV above the ground state of the neutral system. The experiment was conducted by merging monoenergetic electron and ion beams in the heavy ion storage ring CRYRING. The detachment channel was monitored by detecting neutral C4 fragments.
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| 3. |
- Fritioff, K, et al.
(författare)
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Single and double detachment from H-
- 2004
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622 .- 2469-9926 .- 2469-9934. ; 69:4, s. 042707-
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Tidskriftsartikel (refereegranskat)abstract
- Absolute cross sections for single and double detachment from H- following electron impact have been measured over a range of collision energies from the thresholds to 170 eV. The measurements were made using a magnetic storage ring. The ions in the ring were merged with a monoenergetic electron beam and neutral and positively charged fragments were detected. We cover larger energy ranges than in many of the previous experiments, and this is the first time both single and double detachment have been measured simultaneously. This allows us to present accurate ratios between the single and double detachment cross sections. On the basis of these ratio measurements we discuss possible mechanisms leading to double detachment.
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| 4. |
- Kalhori, S., et al.
(författare)
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Resonant ion-pair formation in electron collisions with rovibrationally cold H-3(+)
- 2004
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 69:2, s. 022713-
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Tidskriftsartikel (refereegranskat)abstract
- Experimental and theoretical cross sections for the resonant ion-pair formation (RIP) in electron collisions with rovibrationally cold H-3(+) ions are presented. Absolute cross sections for the RIP process producing H- ions are measured for center-of-mass energies between 2-20 eV using the CRYRING, heavy-ion storage ring. Theoretical cross sections are obtained using wave-packet propagation on both one- and two-dimensional models of relevant diabatic-potential energy surfaces and couplings of H-3(+) and H-3.
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| 5. |
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| 6. |
- Aberg, J, et al.
(författare)
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Electrical properties of the TiSi2-Si transition region in contacts : The influence of an interposed layer of Nb
- 2001
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 90:5, s. 2380-2388
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Tidskriftsartikel (refereegranskat)abstract
- The influence of an interposed ultrathin Nb layer between Ti and Si on the silicide formation and the electrical contact between the silicide formed and the Si substrate is investigated. The presence of the Nb interlayer results in the formation of ternary alloy (Nb,Ti)Si-2 in the C40 crystallographic structure adjacent to the Si substrate. Depending on the nature of the Si substrates and/or the amount of the initial Nb, the interfacial C40 (Nb,Ti)Si-2 leads, in turn, to either epitaxial growth of a highly faulted metastable C40 TiSi2 or formation of the desired C54 TiSi2 at a lower temperature than needed for it to form in reference samples with Ti deposited directly on Si. On p-type substrates doped to various concentrations, the Nb also leads to a considerably lower specific contact resistivity than that obtained in the reference samples: a twofold to fourfold reduction in the contact resistivity is found using cross-bridge Kelvin structures in combination with two-dimensional numerical simulation. As C40 (Nb,Ti)Si-2 forms at the interface when an interfacial Nb is present, the interface characterized is likely to represent the one between (Nb,Ti)Si-2 and Si. For the reference samples, the interface studied is between TiSi2 and Si.
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| 7. |
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| 9. |
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| 10. |
- Friedlein, Rainer, et al.
(författare)
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Surface-induced vertical alignment of self-assembled supramolecular columns of large polycyclic aromatic hydrocarbons and porphyrins
- 2004
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Ingår i: Synthetic metals. - : Elsevier BV. - 0379-6779 .- 1879-3290. ; 147:01-Mar, s. 79-83
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Tidskriftsartikel (refereegranskat)abstract
- Ordered films of polycyclic aromatic hydrocarbons (PAHs) and porphyrins with functional (e.g. thiophene) side-groups are good candidates for (opto-)electronic applications where fast charge separation and transport are required. Such highly ordered thin films of PAHs, including discotic hexa-peri-hexabenzocoronene (HBC) and C-132-C-16,C-4, as well as brominated functionalized porphyrin molecules have been grown from solutions on semi-metallic molybdenum disulfide substrates and characterized by angle-resolved valence band photoelectron spectroscopy. A vertical growth of self-assembled supramolecular columns perpendicular to the basal plane of the substrate along with their lateral ordering on the surface has been achieved. Annealing made it possible to increase the structural order in the HBC columns, with molecules positioned at a regular offset from the columnar axis. This permitted the formation of extended pi-electronic states with a bandwidth of at least 0.1-0.2 eV at room temperature. (C) 2004 Elsevier B.V. All rights reserved.
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