| 1. |
- Collaboration, The PANDA, et al.
(författare)
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Feasibility studies of time-like proton electromagnetic form factors at PANDA at FAIR
- 2016
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Ingår i: European Physical Journal A. - : Springer Publishing Company. - 1434-6001 .- 1434-601X. ; 52:10
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Tidskriftsartikel (refereegranskat)abstract
- Simulation results for future measurements of electromagnetic proton form factors at P ¯ ANDA (FAIR) within the PandaRoot software framework are reported. The statistical precision with which the proton form factors can be determined is estimated. The signal channel p¯ p→ e+e- is studied on the basis of two different but consistent procedures. The suppression of the main background channel, i.e.p¯ p→ π+π-, is studied. Furthermore, the background versus signal efficiency, statistical and systematical uncertainties on the extracted proton form factors are evaluated using two different procedures. The results are consistent with those of a previous simulation study using an older, simplified framework. However, a slightly better precision is achieved in the PandaRoot study in a large range of momentum transfer, assuming the nominal beam conditions and detector performance.
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| 2. |
- Singh, B., et al.
(författare)
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Feasibility study for the measurement of pi N transition distribution amplitudes at (P)over-barANDA in (P)over-barp -> J/psi pi(0)
- 2017
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Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 95:3
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Tidskriftsartikel (refereegranskat)abstract
- The exclusive charmonium production process in (P) over barp annihilation with an associated pi 0 meson (p) over barp -> J/psi pi(0) is studied in the framework of QCD collinear factorization. The feasibility of measuring this reaction through the J/psi -> e(+) e(-) decay channel with the AntiProton ANnihilation at DArmstadt ((P) over bar ANDA) experiment is investigated. Simulations on signal reconstruction efficiency as well as the background rejection from various sources including the (P) over barp -> pi(+)pi(-)pi(0) and (p) over barp -> J/psi pi(0)pi(0) reactions are performed with PANDAROOT, the simulation and analysis software framework of the (P) over bar ANDA experiment. It is shown that the measurement can be done at (P) over bar ANDA with significant constraining power under the assumption of an integrated luminosity attainable in four to five months of data taking at the maximum design luminosity.
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| 3. |
- Singh, B., et al.
(författare)
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Study of doubly strange systems using stored antiprotons
- 2016
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Ingår i: Nuclear Physics A. - : Elsevier. - 0375-9474 .- 1873-1554. ; 954, s. 323-340
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Tidskriftsartikel (refereegranskat)abstract
- Bound nuclear systems with two units of strangeness are still poorly known despite their importance for many strong interaction phenomena. Stored antiprotons beams in the GeV range represent an unparalleled factory for various hyperon-antihyperon pairs. Their outstanding large production probability in antiproton collisions will open the floodgates for a series of new studies of systems which contain two or even more units of strangeness at the PANDA experiment at FAIR. For the first time, high resolution gamma-spectroscopy of doubly strange Lambda Lambda-hypernuclei will be performed, thus complementing measurements of ground state decays of Lambda Lambda-hypernuclei at J-PARC or possible decays of particle unstable hypernuclei in heavy ion reactions. High resolution spectroscopy of multistrange Xi(-) -atoms will be feasible and even the production of Omega(-) -atoms will be within reach. The latter might open the door to the vertical bar S vertical bar = 3 world in strangeness nuclear physics, by the study of the hadronic Omega(-) -nucleus interaction. For the first time it will be possible to study the behavior of Xi(+) in nuclear systems under well controlled conditions.
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| 4. |
- Beutler, A., et al.
(författare)
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Adsorption properties of a mixed surface studied by high resolution core level photoemission : CO/0.5 ML Pd/Rh(111)
- 1998
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Ingår i: Surface Science. - 0039-6028. ; 411:1-2, s. 111-122
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Tidskriftsartikel (refereegranskat)abstract
- The coverage-dependent adsorption properties of a laterally heterogeneous bimetallic surface have been investigated by high resolution core level photoemission and low energy electron diffraction. The specific system under study was CO adsorbed on a Rh(111) surface onto which 2D Pd islands (coverage 0.5 ML) were formed by vapor deposition. The CO adsorption properties of the heterogeneous surface were compared with CO adsorption on a Rh(111) surface covered with a full Pd monolayer and with previous results for the CO/Rh(111) system. For low exposures CO is only found on the Rh(111) patches which can be explained by diffusion of CO from the Pd islands onto Rh parts in the adsorption process. At higher exposures CO diffusion from Rh to Pd is indicated. The origin of the diffusion processes can be found in the different coverage-dependent CO adsorption energies on the two surface parts.
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| 5. |
- Beutler, A., et al.
(författare)
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Identification of a laterally mobile state during CO adsorption
- 2000
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Ingår i: Journal of Physics: Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 12:6, s. 765-772
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated CO adsorption at 300 K on ∼ 1.5 atomic layer thick Pd films on a Mo(110) surface by high-resolution core level photoemission. We describe how high-resolution core level spectroscopy may be utilized to study the influence of laterally mobile states on the sticking probability of molecules on such a laterally heterogeneous surface. The present Pd films are laterally heterogeneous in the sense that the additional ∼ 0.5 atomic Pd layer forms mesoscopic one-layer thick islands on top of the first Pd layer. At 300 K, CO chemisorbs on these two-layer thick islands but not on the one-layer parts of the film. The rate at which these two-layer islands are filled by CO molecules as the surface is exposed to CO is found to be consistent with a picture where CO molecules that initially impinge on the one-layer parts of the surface enter a laterally mobile state and diffuse to the two-layer islands and adsorb there. This mobile state is in many respects similar to a classical precursor state.
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| 6. |
- Beutler, A., et al.
(författare)
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The influence of preadsorbed oxygen on the adsorption of CO on two-dimensional Pd islands on a Rh (111) surface
- 1998
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Ingår i: Surface Science. - 0039-6028. ; 418:2, s. 457-465
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Tidskriftsartikel (refereegranskat)abstract
- The influence of preadsorbed oxygen on the CO adsorption properties of a laterally heterogeneous bimetallic surface consisting of Pd islands on Rh(111) at a Pd coverage of 0.5 monolayers has been studied by high resolution core level photoemission. A surface consisting of clean Pd islands surrounded by oxygen-covered Rh(111) patches was prepared by predosing oxygen at room temperature. By applying core level photoemission to the Pd 3d5/2 and the C 1s levels, the adsorption of CO on this surface was studied with particular attention being paid to possible CO diffusion between the two surface parts. The CO molecules are found to diffuse from the oxygen-covered Rh(111) patches onto the Pd islands for low to medium CO exposures. This diffusion direction is opposite of that found previously for the 0.5 ML Pd on Rh(111) system with no oxygen predosing. This reversal of the diffusion direction is argued to be due to a large reduction of the CO adsorption energy on the Rh patches of the surface caused by the preadsorbed oxygen.
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| 7. |
- Jaworowski, A. J., et al.
(författare)
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Adsorption sites in O and CO coadsorption phases on Rh(111) investigated by high-resolution core-level photoemission
- 1999
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Ingår i: Surface Science. - 0039-6028. ; 431:1, s. 33-41
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution core-level spectroscopy is used in combination with low-energy electron diffraction (LEED) and photoelectron diffraction to identify the adsorption sites for three different coadsorbed phases consisting of ordered overlayers of oxygen coadsorbed with CO on the Rh(111) single-crystal surface. The three ordered overlayer structures, which may be denoted as 2O + CO/Rh(111), O + CO/Rh(111) and O+2CO/Rh(111), all show (2 × 2) LEED patterns. In the 2O + CO and O + CO phases the CO molecules are found to occupy only on-top sites while the O + 2CO phase shows CO molecules in both on-top and three-fold hollow sites. In all cases the oxygen atoms are found in three-fold hollow sites. For the O + CO and O + 2CO phases our results confirm previous determinations by LEED, while the 2O + CO phase has not been observed before on Rh(111). The core-level binding energies of the C 1s and O 1s core levels for both adsorbates are characteristics of the adsorption site and are very close to the binding energies found for the pure cases of only oxygen or CO adsorbed on Rh(111). In the coadsorption phases we find that the interaction between the adsorbates has only a minor influence on the core-level binding energies. For the O + 2CO/Rh(111) coadsorption phase we find that a full CO coverage is not obtained; less than 80% of the unit cells contain two CO molecules, in line with previous findings.
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| 8. |
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| 9. |
- Strisland, F., et al.
(författare)
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Adsorption sites in coadsorption systems determined by photoemission spectroscopy : K and CO coadsorbed on Rh(111)
- 1998
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Ingår i: Surface Science. - 0039-6028. ; 410:2-3, s. 330-343
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption sites of coadsorbed K and CO on the Rh(111) surface have been determined using high-resolution core-level spectroscopy, low-energy electron diffraction and site-resolved photoelectron diffraction. For both a (2 × 2)-2CO-1K and a (2√3 × 2√3)-6CO-1K structure, we find that the CO molecules occupy threefold hollow sites and the K atoms on-top sites, contrary to the adsorption sites of K (threefold hollow site) and CO (on-top site below 0.5 monolayers) if adsorbed alone on Rh(111). Deposition of K onto a CO precovered surface is found to induce large shifts towards lower binding energy of the C and O 1s core levels (∼0.7 eV for C 1s and ∼1.5 eV for O 1s). The major part of these shifts is shown to arise from the K-induced site change of the CO molecules. This finding may be of importance in the interpretation of XPS data of related co-adsorption systems. Finally, it is suggested that the C and O 1s binding energies provide useful fingerprints of the CO adsorption site also for co-adsorption systems.
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| 10. |
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| 11. |
- Jaworowski, A J, et al.
(författare)
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Determination of NO adsorption sites on Pd(100) using core level photoemission and low energy electron diffraction
- 2002
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Ingår i: Surface Science. - 0039-6028. ; 501:1-2, s. 74-82
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption of NO on Pd(1 0 0) is investigated with high resolution core level spectroscopy and low energy electron diffraction (LEED). Several ordered NO overlayers were observed, in agreement with earlier Studies. Our data clearly show that NO adsorbs in fourfold hollow sites at coverages tip to 0.25 -0.30 monolayer (ML) whereas at 0.5 ML only bridge sites are occupied. By a reinterpretation of previous electron energy loss spectroscopy (EELS) investigations we show that the new site assignments are in agreement the EELS data, Based on the photoemission results for the N 1s and the Pd 3d core levels we propose new structure models for the (2root2 x 2root2)R45degrees and the p(4 x 2) LEED patterns found at coverages of 0.5 and 0.25 ML, respectively. In the latter case, it is suggested that the p(4 x 2) LEED pattern is formed from domains having p(2 x 2)-NO and c(4 x 2)-2NO unit cells.
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| 12. |
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| 13. |
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| 14. |
- Jaworowski, Alexander J
(författare)
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Structural Properties of Palladium-Manganese Alloys
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Structural properties of adsorbed overlayers on well-defined single crystals and of Palladium-Manganese surface alloys formed on Pd(100) have been investigated using synchrotron-based photoemission, scanning tunneling microscopy and Fourier-transform infrared spectroscopy. The experimental valence electronic structure of PdMn systems on Pd(100) is compared to density functional calculations (DFT). It is shown that room temperature growth and alloying of Mn on Pd(100) undergoes a two-dimensional to three-dimensional transition. Pd 3d photoemission results show that the 2D c(2x2) alloy contains subsurface Mn and the alloy was found to be terminated by a PdMn mixed layer. Total energy calculations demonstrate that a Pd-terminated Cu3Au structure is energetically more favorable, but the system is not able to reach this state at the used temperature due to kinetic effects. It could be concluded that a flat Mn monolayer formed at 90 K is anti-ferromagnetic in line with earlier predictions. When concerning the annealed 2D c(2x2) alloy, the best agreement was found for a structure with PdMn mixed layers as the two outermost layers. The changes in the NO adsorption properties of Mn modified Pd(100) have been investigated using high resolution core level photoemission. NO adsorption on the alloy films was found to destroy the c(2x2) structure. In the case of a surface partly modified by Mn, dissociation at boundaries was found to be most important. Adsorption and reactions of CO, CO2, O2 and NO on a 3D c(2x2)-PdMn surface was studied using photoelectron spectroscopy. The c(2x2) alloy structure was destroyed by O2 and NO adsorption, which involves formation of MnOx on the surface, and these aggregates are crucial for subsequent reactions. Results are also presented that demonstrate that a pseudomorphic two-layer-thick c(2x2) PdMn alloy can be grown on W(110). Investigations of small molecules adsorbed on Pd(100), Rh(111) and Mo(110) surfaces are also presented. Structural models are proposed for NO adsorption on Pd(100) and for the O and CO coadsorption system on Rh(111). The dissociation of CO adsorbed on Mo(110) was studied in detail by core level photoemission.
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| 15. |
- Jaworowski, Åsa, et al.
(författare)
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Calponin reduces shortening velocity in skinned taenia coli smooth muscle fibres
- 1995
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Ingår i: FEBS Letters. - 1873-3468. ; 365:2-3, s. 167-171
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Tidskriftsartikel (refereegranskat)abstract
- Calponin (4.1-5.9 microM, pig stomach) inhibited maximal shortening velocity (Vmax) by 20-25% with only minor influence on force in skinned smooth muscle from guinea-pig taenia coli activated at different Ca2+ levels and with thiophosphorylation. Similar results were obtained with a fragment of the N-terminal 1-228 amino acids engineered using a mouse cDNA construct (5.4 microM). Both the native calponin and the fragment inhibited actin filament sliding in a graded manner in an in vitro motility assay. We conclude that calponin influences the kinetics of the actin-myosin interaction in the organised smooth muscle contractile system and that engineered fragments of calponin can be used to probe its action in muscle fibres. The effects can be due to an introduction of an internal load during filament sliding, possibly by decreasing the detachment rates and increasing the cross-bridge time spent in the attached state.
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| 16. |
- Sandell, A., et al.
(författare)
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Adsorption of acetylene and hydrogen on Pd(111) : Formation of a well-ordered ethylidyne overlayer
- 1998
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Ingår i: Surface Science. - 0039-6028. ; 415:3, s. 411-422
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Tidskriftsartikel (refereegranskat)abstract
- The C2H2(+H)/Pd(111) system has been studied using high resolution core level spectroscopy and low energy electron diffraction (LEED). Two ordered phases were found when adsorbing C2H2 at 125 K, giving rise to a (2 × 2) and a (√3 × √3)R30° LEED pattern, respectively. When preadsorbing H at 110-150 K, the sticking probability of the C2H2 molecules is strongly reduced and only the (√3 × √3)R30° overlayer is formed. In all three of the ordered structures the C2H2 molecules are suggested to occupy the hollow sites. Heating of the (√3 × √3)R30° C2H2 + H layer to 350 K yields a well ordered (√3 × √3)R30° overlayer consisting exclusively of ethylidyne (CCH3) positioned in the hollow sites. The formation of ethylidyne is furthermore found to be preceded by the formation of an intermediate species ("β") which probably is vinylidene.
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| 17. |
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| 18. |
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| 19. |
- Wiklund, M, et al.
(författare)
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Vibrational fine structure in the C 1s photoemission spectrum of the methoxy species chemisorbed on Cu(100)
- 1998
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Ingår i: Surface Science. - 0039-6028. ; 418:1, s. 210-218
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Tidskriftsartikel (refereegranskat)abstract
- The C 1s photoemission spectrum of methoxy (CH3O) chemisorbed on Cu(100) is demonstrated to contain a resolvable fine structure due to excitation of the molecular C-H normal vibrational mode. The origin of the fine structure is ascertained by substituting hydrogen with deuterium in the methoxy overlayers and by comparison to gas-phase C 1s spectra for methanol (CH3OH). The vibrational fine structure is demonstrated to provide a fingerprint of the hydrocarbon group present on the surface.
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| 20. |
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