| 1. |
- Abulaiti, Yiming, et al.
(författare)
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Search for an invisibly decaying Higgs boson or dark matter candidates produced in association with a Z boson in pp collisions at root s=13 TeV with the ATLAS detector
- 2018
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445 .- 0009-2614 .- 1873-4448. ; 776, s. 318-337
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Tidskriftsartikel (refereegranskat)abstract
- A search for an invisibly decaying Higgs boson or dark matter candidates produced in association with a leptonically decaying Z boson in proton-proton collisions at root s = 13 TeV is presented. This search uses 36.1 fb(-1) of data collected by the ATLAS experiment at the Large Hadron Collider. No significant deviation from the expectation of the Standard Model backgrounds is observed. Assuming the Standard Model ZH production cross-section, an observed (expected) upper limit of 67% (39%) at the 95% confidence level is set on the branching ratio of invisible decays of the Higgs boson with mass m(H) = 125 GeV. The corresponding limits on the production cross-section of the ZH process with the invisible Higgs boson decays are also presented. Furthermore, exclusion limits on the dark matter candidate and mediator masses are reported in the framework of simplified dark matter models.
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| 2. |
- Andersson, Stefan, 1973, et al.
(författare)
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Tunneling in hydrogen and deuterium addition to CO at low temperatures
- 2011
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Ingår i: Chemical physics letters. - : Elsevier BV. - 0009-2614. ; 513:1-3, s. 31-36
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Tidskriftsartikel (refereegranskat)abstract
- The hydrogen and deuterium atom addition reactions of CO to form HCO and DCO are addressed by Harmonic Quantum Transition State Theory calculations. Special attention is paid to the reactions at very low temperatures (5–20 K) where it is found that quantum tunneling leads to substantial rates of reaction. This supports experiments in the solid phase, which conclude that these reactions are driven by tunneling at low temperatures. The calculated kinetic isotope effect of kD/kH = 1/250 is found to be lower than the experimentally deduced value of 0.08 for the surface reaction. Possible reasons for this discrepancy are discussed.
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| 3. |
- Anselmo, Ana Sofia, 1980-, et al.
(författare)
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Photodegradation of the electronic structure of PCBM and C60 films in air
- 2016
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Ingår i: Chemical Physics Letters. - : Elsevier. - 0009-2614 .- 1873-4448. ; 652, s. 220-224
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Tidskriftsartikel (refereegranskat)abstract
- Fullerenes are common electron acceptors in organic solar cells. Here the photostability in air of the electronic structures of spin-coated PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) and evaporated C60 films are studied using ultraviolet photoelectron spectroscopy (UPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. After exposing these materials in air to simulated sunlight, the filled and empty molecular orbitals are strongly altered, indicating that the conjugated π-system of the C60-cage has degraded. Even a few minutes in normal lab light induces changes. These results stress the importance of protecting fullerene-based films from light and air during processing, operation, and storage.
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| 4. |
- Baryshnikov, Glib V., et al.
(författare)
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Anion-induced exchange interactions in binuclear complexes of Cu(II) with flexible hexadentate bispicolylamidrazone ligands
- 2016
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Ingår i: Chemical Physics Letters. - : Elsevier. - 0009-2614 .- 1873-4448. ; 661, s. 48-52
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Tidskriftsartikel (refereegranskat)abstract
- Two recently synthesized copper(II) complexes with spacer-armed bispicolylamidrazone ligands have been theoretically studied at the density functional theory (DFT) level accounting for empirical dispersion correction and intrinsic anionic environment by perchlorate ions. The exchange parameter between the open-shell singlet and triplet states of the studied complexes has been estimated by broken symmetry DFT calculations. The mechanism of spin-spin exchange interaction between the unpaired electrons via the σ-bond aliphatic chain (Gusev et al., 2015) is confirmed. Instead, a anion-induced mechanism is proposed which means that the anionic grid participates in the exchange interaction between the unpaired electrons.
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| 5. |
- Beke-Somfai, Tamas, 1977, et al.
(författare)
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Energy phase shift as mechanism for catalysis
- 2012
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 535, s. 169-172
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Tidskriftsartikel (refereegranskat)abstract
- Catalysts are agents that by binding reactant molecules lower the energy barriers to chemical reaction. After reaction the catalyst is regenerated, its unbinding energy recruited from the environment, which is associated with an inevitable loss of energy. We show that combining several catalytic sites to become energetically and temporally phase-shifted relative to each other provides a possibility to sustain the overall reaction by internal 'energy recycling', bypassing the need for thermal activation, and in principle allowing the system to work adiabatically. Using an analytical model for superimposed, phase-shifted potentials of F-1-ATP synthase provides a description integrating main characteristics of this rotary enzyme complex.
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| 6. |
- Belghit, R., et al.
(författare)
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First principles study of structural, mechanical and electronic properties of the ternary alkali metal oxides KNaO and RbNaO
- 2018
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Ingår i: Chemical Physics Letters. - : Elsevier. - 0009-2614 .- 1873-4448. ; 706, s. 684-693
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Tidskriftsartikel (refereegranskat)abstract
- The structural, mechanical and electronic properties of the ternary inter-alkali metal oxides KNaO and RbNaO compounds are investigated by using first principle calculations. The structural parameters and atomic positions are in agreement with the experimental values. The bulk, shear and Young moduli, Poisson's ratio, Lame coefficients and Debye temperature have been calculated. The elastic parameters indicate that these compounds have ductile behavior. The calculated band structures indicate that KNaO and RbNaO have an indirect energy band gap. The charge density distributions reveal an anionic character. This theoretical study is likely to stimulate future experimental researches.
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| 7. |
- Belyanin, Maxim L., et al.
(författare)
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Design, synthesis and evaluation of a new Mn - Contrast agent for MR imaging of myocardium based on the DTPA-phenylpentadecanoic acid complex
- 2016
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 665, s. 111-116
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Tidskriftsartikel (refereegranskat)abstract
- In the present paper we describe the first synthesis and evaluation of a novel Mn (II) complex (DTPA-PPDA Mn (II)) which contains a C-15 fatty acid moiety that has high affinity to the heart muscle. The complexation energy of DTPA-PPDA Mn (II) evaluated by quantum chemistry methodology indicates that it essentially exceeds the corresponding value for the known DTPA Mn (II) complex. Molecular docking revealed that the affinity of the designed complex to the heart-type transport protein H-FABP well exceeds that of lauric acid. Phantom experiments in low-field MRI the designed contrast agent provides MR imaging comparable to gadopentetic acid.
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| 8. |
- Borgström, Magnus, et al.
(författare)
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Dynamics of extremely anisotropic etching of InP nanowires by HCl
- 2011
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 502:4-6, s. 222-224
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Tidskriftsartikel (refereegranskat)abstract
- We report on the dynamics of in situ etching of nanowires using an etching agent which allows for parameter optimization for nanowire synthesis without concerns of tapering issues. Upon etching of InP nanowires using HCl it is found that HCl mainly reacts with the precursor TMI, its decomposition species, and physisorbed In. The reaction with solid InP is less rapid and diffusion limited. We find a gas-phase etch process which is metal assisted and has a high aspect ratio of 1:100. (C) 2011 Elsevier B.V. All rights reserved.
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| 9. |
- Borin, Antonio Carlos, et al.
(författare)
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Electronic structure and chemical bonding in W-2 molecule
- 2010
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 490:1-3, s. 24-28
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of the lowest-lying electronic states of W-2 were investigated at the CASPT2 level. The ground state is a X-1 Sigma(+)(g) state, followed by the a(3)Delta(u), b(3)Sigma(+)(u) and A(1)Delta(u) electronic states. Seven low-lying Omega-states were computed: (1)0(g)(+), (2)3(u), (3)2(u), (4)1(u), (5)0(u)(-), (6)1(u), and (7)2(u), with the ground state corresponding to the (1)0(g)(+)(X-1 Sigma(+)(g)) state. Comparison with the other VIB transition metal group dimers indicates a common pattern of electronic structure and spectroscopic properties. (C) 2010 Elsevier B.V. All rights reserved.
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| 10. |
- Boukaoud, A., et al.
(författare)
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Inelastic neutron scattering of methyl tunnelling in isotopic mixtures of dibromomesitylene
- 2011
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 509:1-3, s. 20-24
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Tidskriftsartikel (refereegranskat)abstract
- In dibromomesitylene, only the methyl group denoted Me-2 and surrounded by two bromine atoms, is a quasi free rotor. In isotopic mixtures the Me-2 tunnelling gap is almost insensitive to variations in temperature and to isotopic dilution. The Me-2 hindering potential remains the same as in the pure material with a main component cos6 theta. Because there is no coupling between the methyl groups, dibromomesitylene provides an illustration of the 'Single Particle Model' in rotational tunnelling. An explanation is given why Density Functional Theory calculations fail to represent the characteristics of tunnelling produced by the Schrodinger equation. (C) 2011 Elsevier B.V. All rights reserved.
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