Search results for "binding energy"
showing 10 items of 248 documents
Circular dichroism in angular resolved photoemission from pure and Rb-doped C60 and C22H14 layers on platinum and tungsten
1997
Abstract Polycrystalline C60 and Pentacene films grown on W(110) and Pt(111) have been studied in valence band photoemission using circularly polarised synchrotron radiation from BESSY with special emphasis on circular dichroism in photoemission. For thin films of C60, dichroic asymmetries of about 10% occur independent of the temperature and the substrate hinting that the rotation of the topmost layer is hindered even at room temperature. For Pentacene we found asymmetries up to 50% in the region of the σ-electrons. Moreover, we found for this molecule a dichroic asymmetry in normal emission, that is a forbidden geometry. This hints on adsorption with the molecules perpendicularly oriented…
Quantum-well states in ultrathin Ag(111) films deposited onto H-passivated Si(111)-(1x1) surfaces
2002
Ag(111) films were deposited at room temperature onto H-passivated Si(111)-(1x1) substrates, and subsequently annealed at 300 C. An abrupt non-reactive Ag/Si interface is formed, and very uniform non-strained Ag(111) films of 6-12 monolayers have been grown. Angle resolved photoemission spectroscopy has been used to study the valence band electronic properties of these films. Well-defined Ag sp quantum-well states (QWS) have been observed at discrete energies between 0.5-2eV below the Fermi level, and their dispersions have been measured along the GammaK, GammaMM'and GammaL symmetry directions. QWS show a parabolic bidimensional dispersion, with in-plane effective mass of 0.38-0.50mo, along…
Positron trapping rate into vacancy clusters
1979
The trapping rate of positrons into vacancy clusters in metals has been calculated. It increases with the trap size and binding energy and approximately scales with the number of vacancies in small clusters. The phonon-mediated contribution to the trapping rate is small. The temperature dependence of the trapping process is discussed.
Singlet and triplet excitons in conjugated polymers.
1992
Exciton states in conjugated polymers are theoretically studied in the Su-Schrieffer-Heeger model supplemented by long-range Coulomb interactions. The relationship between exciton energies and basic interaction parameters is clarified, demonstrating the special nature of one-dimensional excitons. The binding energies of the lowest singlet and triplet excitons depend sensitively upon the on-site Coulomb energy. Relevant experiments in polydiacetylene can be explained by the present model using moderate interaction strength.
Ion traps in nuclear physics—Recent results and achievements
2016
Abstract Ion traps offer a way to determine nuclear binding energies through atomic mass measurements with a high accuracy and they are routinely used to provide isotopically or even isomerically pure beams of short-living ions for post-trap decay spectroscopy experiments. In this review, different ion-trapping techniques and progresses in recent nuclear physics experiments employing low-energy ion traps are discussed. The main focus in this review is on the benefit of recent high accuracy mass measurements to solve some key problems in physics related to nuclear structure, nuclear astrophysics as well as neutrinos. Also, several cases of decay spectroscopy experiments utilizing trap-purifi…
Ion traps in nuclear physics : recent results and achievements
2016
Ion traps offer a way to determine nuclear binding energies through atomic mass measurements with a high accuracy and they are routinely used to provide isotopically or even isomerically pure beams of short-living ions for post-trap decay spectroscopy experiments. In this review, different ion-trapping techniques and progresses in recent nuclear physics experiments employing low-energy ion traps are discussed. The main focus in this review is on the benefit of recent high accuracy mass measurements to solve some key problems in physics related to nuclear structure, nuclear astrophysics as well as neutrinos. Also, several cases of decay spectroscopy experiments utilizing trap-purified ion sa…
Coin metal adsorption on defective MgO(001) surface: ab initio study
2005
First principles slab calculations have been performed for Ag and Cu adsorption on periodically distributed point defects (a single O2– or Mg2+ vacancy per 2×2 surface supercell) on the non-polar MgO(001) substrate. Using the procedure implemented in the CRYSTAL-03 code, both Fs and Vs centers were modeled by retaining in the vacancy the basis set of the missing O2– and Mg2+ ions, respectively, with the local relaxation of the nearest substrate ions. Adsorption of metal atom over the Fs center (2.4 eV vs. 2.1 eV per Cu and Ag adatoms, respectively) is much stronger as compared with regular O2− sites (0.6 eV vs. 0.4 eV, respectively). The Fs center donates a substantial charge towards Ag and…
Anomalous binding sequence of CO ligands to an anionic triplatinum carbonyl complex
2005
Abstract A systematic density functional theory study on the structures and binding energies of triplatinum carbonyls Pt 3 ( CO ) x q , with x = 1–6 and q = 0, −1, reveals an anomalous trend in binding energies of the CO ligands to the triangular platinum core, with the first three ligands strongly bound at terminal Pt sites, followed by weaker bound ligands at Pt–Pt bridge sites for x = 4–6. This work provides a novel explanation to the anomalous CO binding trend reported in mid-1990s from collision-induced dissociation and photodissociation experiments.
Properties of small clusters at ionic surfaces: (NaCl)nclusters (n=1–48) at the (100) MgO surface
1995
We have studied the geometry, binding energy, interaction with the surface, barriers for diffusion, optical absorption, and the possibility for their observation using atomic force microscopy of (NaCl${)}_{\mathit{n}}$ clusters (n=1--48) on the (100) MgO surface. We address the questions at which cluster size do the adsorbed molecules lose their identity and how do strained clusters accommodate the strain. The relation between the structure of initial molecular fragments adsorbed at the surface and the structure of the corresponding thick film is discussed. The results are compared with the calculated structures of the free clusters and the experimental data on the molecular-beam epitaxy of…
<title>Shallow electron traps in alkali halide crystals: Mollwo-Ivey relations of the optical absorption bands</title>
2001
Evidences are given that two classes of the transient IR- absorption bands: (a) with max. at 0.27-0.36 eV in NaCl, KCl, KBr, KI and RbCl (due to shallow electron traps according G. Jacobs or due to bound polarons according E.V. Korovkin and T.A. Lebedkina) and (b) with max. at 0.15-0.36 eV in NaI, NaBr, NaCl:I, KCl:I, RbCl:I and RbBr:I (due to on-center STE localized at iodine dimer according M. Hirai and collaborators) are caused by the same defect- atomic alkali impurity center [M+]c0e- (electron e- trapped by a substitutional smaller size alkali cation impurity [M+]c0). The Mollwo-Ivey plots (for the transient IR-absorption bands) of the zero-phonon line energy E0 (for NaCl, KCl, KBr, Rb…