| 1. |
- Andersson, T., et al.
(author)
-
Selective adsorption, bound states, and potential parameters for He, Ne, and Ar interacting with a Cu(110) surface
- 2006
-
In: J. Chem. Phys.. - : AIP Publishing. - 0021-9606. ; 124
-
Journal article (peer-reviewed)abstract
- Using nozzle beams of He, Ne, and Ar, we have measured diffractive selective adsorption resonances from a Cu(110) surface kept at 20 K. Bound state energies of the atom-surface potentials have been determined from plots of the measured resonance energies versus incident angle and their fits to calculated kinematical dispersion relations. For 3He and 4He we have found a unique level assignment that is compatible with a single gas-surface potential curve with a well depth of 6.05 meV of the He–Cu(110) potential. This value is about 10% larger than the prediction of 5.55 meV from the current physisorption theory. The Ne and Ar data reveal a large number of closely spaced levels with level separations and estimated van der Waals coefficients that are compatible with available theoretical data.
|
|
| 2. |
- Andersson, Malte, 1941, et al.
(author)
-
”Minskande befolkning är inte problemet”
- 2020
-
In: Dagens Nyheter. ; :1 augusti, DN-debatt
-
Journal article (pop. science, debate, etc.)abstract
- Nätverket Population Matters Sweden: En uppmärksammad studie i The Lancet pekar mot en lägre befolkningsökning i världen än tidigare prognoser. Men en miljard människor till är fortfarande långt över vad jorden klarar. Befolkningstrenden måste snarare vända neråt, och det kräver åtgärder för att stärka kvinnors rättigheter världen över.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Andersson, Stig, 1941, et al.
(author)
-
Excitation and desorption of physisorbed H2 via the 2Σu electron scattering resonance.
- 2017
-
In: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 147, s. 114703-1-114703-11
-
Journal article (peer-reviewed)abstract
- Our high-resolution electron energy-loss measurements concern physisorbed H2 and comprise dif- ferential cross sections for the excitation of the internal H2 modes and the H2-surface bonding mode and their combinations and extend over the electron impact energy range of the classical low-energy H2 2Σu resonance. Comparison with corresponding data for the excitation of the internal modes of gas phase H2 reveals that strong elastic electron reflectivity from the Cu(100) substrate profoundly distorts the inelastic scattering pattern for physisorbed H2. We find that this influence can be corrected for and that the resulting peak cross sections agree with the H2 gas phase data, in accordance with theoretical predictions for the excitation of the internal H2 vibration. We have used corrected cross sections for the rotational mode spectra of physisorbed H2, HD, and D2 in a model concerning elec- tron induced desorption via rotation-translation energy conversion. These spectra include transitions from the ground state as well as excited levels of the physisorption potential well. H2 and HD can desorb from all levels while D2, for energetic reason, can only desorb from the excited levels. This model gives a satisfactory account of the observed desorption cross sections and predicts character- istic velocity distributions of the desorbing molecules. The cross section data for H2 and HD reveals that direct bound-free transitions also contribute to the electron induced desorption.
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Gustafsson, Kristian, 1972, et al.
(author)
-
Infrared spectroscopy of physisorbed and chemisorbed N-2 in the Pt(111)(3x3)N-2 structure
- 2007
-
In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 127:19
-
Journal article (peer-reviewed)abstract
- Using infrared spectroscopy and low electron energy diffraction, we have investigated the adsorption of N-2, at 30 K, on the Pt(111) and the Pt(111)(1x1)H surfaces. At monolayer coverage, N-2 orders in commensurate (3x3) structures on both surfaces, and we propose that the unit cells contain four molecules in each case. The infrared spectra reveal that N-2 exclusively physisorbs on the Pt(111)(1x1)H surface, while both physisorbed and chemisorbed N-2 is detected on the Pt(111) surface. Physisorbed N-2 is the majority species in the latter case, and the two adsorption states show an almost identical uptake behavior, which indicates that they are intrinsic constituents of the growing (3x3) N-2 islands. An analysis of the infrared absorbance data, based on a simple scaling concept suggested by density functional theory calculations, supports a model in which the (3x3) unit cell contains one chemisorbed molecule in end-on atop configuration and three physisorbed molecules. We note that a classic ''pinwheel'' structure on a hexagonal lattice, with the end-on chemisorbed N2 molecules acting as ''pins,'' is compatible with this composition. (C) 2007 American Institute of Physics.
|
|
| 9. |
|
|
| 10. |
- Hellman, Anders, 1974, et al.
(author)
-
Hydrogen-Induced Reconstruction of Cu(100): Two-Dimensional and One-Dimensional Structures of Surface Hydride
- 2014
-
In: Journal of Physical Chemistry C. - Washington : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:29, s. 15773-15778
-
Journal article (peer-reviewed)abstract
- Adsorption of atomic hydrogen has a remarkable influence on the structure and morphology of the Cu(I00) surface. We have examined two specific situations; the well-known reconstructed p(2 x 2)-H surface and a one-dimensional (6 X 1)-H surface resembling the stripe reconstruction observed in an electrochemical environment. High resolution electron energy loss spectroscopy and density functional calculations show that the H atoms occupy only surface sites and that H bonding in induced 3-fold Cu surface hollow sites is a structural key element. The calculations support a transient scenario in which H absorption in subsurface sites is a critical intermediate step in the reconstruction of the Cu surface. We find clear evidence in terms of characteristic properties, like the H-Cu bond lengths and the dipole excited vibrational mode spectra, that these structures consist of two-dimensional and one-dimensional structures of surface hydride.
|
|
| 11. |
- Lee, Kyuho, et al.
(author)
-
Benchmarking van der Waals density functionals with experimental data: potential-energy curves for H2 molecules on Cu(111), (100) and (110) surfaces
- 2012
-
In: Journal of Physics: Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 24:42
-
Journal article (peer-reviewed)abstract
- Detailed physisorption data from experiment for the H2 molecule on low-index Cu surfaces challenge theory. Recently, density functional theory (DFT) has been developed to account for nonlocal correlation effects, including van der Waals (dispersion) forces. We show that the functional vdW-DF2 gives a potential-energy curve, potential-well energy levels and difference in lateral corrugation promisingly close to the results obtained by resonant elastic backscattering–diffraction experiments. The backscattering barrier is sensitive to the choice of exchange functional approximation. Further, the DFT-D3 and TS-vdW corrections to traditional DFT formulations are also benchmarked, and deviations are analyzed.
|
|
| 12. |
- Lee, Kuyho, et al.
(author)
-
Evaluation of a density functional with account of van der Waals forces using experimental data of H2 physisorption on Cu(111)
- 2011
-
In: Physical Review B. - 1098-0121. ; 84, s. 193408-
-
Journal article (peer-reviewed)abstract
- Detailed experimental data for physisorption potential-energy curves of H2 on low-indexed faces of Cu challenge theory. Recently, density-functional theory has been developed to also account for nonlocal correlation effects, including van der Waals forces. We show that one functional, denoted vdW-DF2, gives a potential-energy curve promisingly close to the experiment-derived physisorption-energy curve. The comparison also gives indications for further improvements of the functionals.
|
|
| 13. |
- Linde, Petter, 1972, et al.
(author)
-
High resolution resonance measurements of the physisorption interaction
- 2006
-
In: Phys. Rev. Lett.. - 0031-9007. ; 96
-
Journal article (peer-reviewed)abstract
- Narrow selective adsorption resonances, with line widths given by the natural lifetime of the intermediate resonance state, have been observed directly in the angular distributions of Ne nozzle beams diffracted from a 20 K Cu(110) surface. Using beams of 20Ne and 22Ne isotopes we show that this high-resolution mode of resonance detection permits, even in a case of a small isotope effect, unique assignment of bound level sequences compatible with a single gas-surface potential curve.
|
|
| 14. |
- Svensson, Krister, 1969-, et al.
(author)
-
Desorption of H-2, HD, and D-2 through Temporary Negative Ion Formation
- 2012
-
In: Physical Review Letters. - Ridge, NY : APS. - 0031-9007 .- 1079-7114. ; 109:19
-
Journal article (peer-reviewed)abstract
- Physically adsorbed H-2, HD, and D-2 desorbs via the low-energy (2)Sigma(+)(u) electron scattering resonance with characteristic electron energy dependent cross sections as we show by desorption and electron energy-loss measurements. Only H-2 and HD desorb, for energetic reasons, via excitation of the j = 0 -> 2 rotational mode and its subsequent decay into free translational motion, while all three isotopes desorb by direct transitions to unbound continuum states, with a probability close to unity and an unexpectedly weak mass dependence similar to m(-1/2).
|
|
| 15. |
- Svensson, Krister, 1969, et al.
(author)
-
Dipole active rotations of physisorbed H2 and D
- 2005
-
In: Physics Reveiw B. - 0163-1829 .- 2469-9969 .- 2469-9950. ; 71
-
Journal article (peer-reviewed)abstract
- We have, in electron-energy-loss measurements, observed dipole activity associated with the j=02 rotational transitions for H2 and D2 physisorbed on a Cu(100) surface and at Au adatoms on this surface. Such dipole transitions, which are forbidden for the free molecules, provide for example, via rotation-translation conversion, channels for infrared photodesorption. Using two simple dipole moment functions, we have, for the bare Cu(100) surface, calculated dipole matrix elements for the rotational transition and its combination mode with the =01 vibrational transition in the physisorption well. Our calculations reveal that the anisotropy of the molecular electronic polarizability induces a significant dynamic dipole coupled to the rotational and rotational-vibrational motion, but are unable to reproduce the measured relative intensities of the corresponding transitions.
|
|
| 16. |
- Svensson, Krister, 1969-, et al.
(author)
-
Fast ortho-para conversion of H2 adsorbed at copper surface step atoms
- 2007
-
In: Phys. Rev. Lett.. - : American Physical Society. - 0031-9007. ; 98:9
-
Journal article (peer-reviewed)abstract
- Ortho-para conversion of H2 adsorbed at the step atoms of a Cu(510) surface proceeds with a short conversion time constant around 1 s as observed in electron-energy-loss measurements of rotational populations. We suggest that this rapid conversion is related to the special character of the adsorption state, which involves a short H2-Cu bond length of 1.8 Å. On the flat Cu(100) surface, conversion is found to occur at active sites, most likely step atoms
|
|
