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  • 1990-1994  (11)
  • 1
    Electronic Resource
    Electronic Resource
    Differences between L3 and L2 x-ray absorption spectra of transition metal compounds (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 6570-6576 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The differences between L3 and L2 edges of 3d and 4d transition metal complexes and compounds in octahedral symmetry are discussed. The main origin of these differences are the multiplet effects due to the coupling of the 2p core wave function and the 3d and 4d valence wave functions. The 3d and 4d spin–orbit coupling is a second origin of difference. For 3d systems the multiplet effects dominate all other interactions and the L3 and L2 edge are completely mixed and reordered. For 4d systems the core hole spin–orbit coupling is large and the L3 and L2 are separated by about 100 eV with a ratio close to 2:1. The differences between the L3 and L2 edge originate from the weight transfer between the t2g and eg peaks due to the multiplet effect. This weight transfer is about 25% for the L3 edge and about 5% for the L2 edge, which implies that for a comparison to single-particle calculations the L2 edge is preferable to use. Partly filled 4d systems are low-spin and the occupation of the t2g states implies a decrease of the first peak. This decrease is stronger for the L2 edge, implying an increase in the L3:L2 ratio. For 4d5 systems transitions to the t2g hole are only possible at the L3 edge due to the combined effects of 4d spin–orbit coupling and the dd multiplet effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468351
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Performance of the high-resolution SX700/II monochromator (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 80-89 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article reports on the high-resolution performance of the grazing-incidence plane grating monochromator SX700/II, installed at BESSY by the Freie Universität Berlin, in the photon energy range from about 40 to 900 eV. The high resolving power up to 10 000 achieved with this monochromator is based on improving the figure error of the ellipsoidal focusing mirror, on reducing the vertical dimension of the beam source, and on employing a 5-μm exit slit. We report on high-resolution gas-phase studies in the double-excitation region of He, as well as at core-excitation thresholds of Ne, Ar, Kr, and Xe in the photon-energy range from (approximately-equal-to)45 eV to (approximately-equal-to)900 eV. In addition, high-resolution core-excitation spectra at the K thresholds of C, N, and O are presented for gas-phase CO, N2, and O2. In all cases, high-n Rydberg states and/or vibrational sidebands of the electronic excitations were resolved. The various contributions to the present instrumental linewidths are discussed as well as the prospects for further improvements in resolution with this monochromator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142615
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Status and perspectives of high-resolution spectroscopy in the soft x-ray range (invited) : Proceedings of the 4th International Conference on Synchrotron Radiation Instrumentation (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 1234-1240 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The present status in high-resolution photoabsorption and photoemission spectroscopy using synchrotron radiation in the soft x-ray range (40 eV≤hν≤1000 eV) is described. With the SX700/II monochromator, operated by the Freie Universität Berlin at the Berliner Elektronenspeicherring für Synchrotronstrahlung (BESSY), a resolving power of up to ≥10 000 has been achieved. A practical feature of this monochromator is given by the fact that excellent energy resolution is achieved with a single 1221-lines/mm grating in the whole soft x-ray range considered. This opens up new opportunities in core-level photoabsorption spectroscopy of atoms, molecules, adsorbed species, and solids. A combination of the SX700/II beam line with a high-resolution electron spectrometer (ΔE(approximately-equal-to)15 meV) enables resonant photoemission studies of rare-earth materials in the 4d→4f giant-resonance region with unprecedented resolution and also at the 3d→4f absorption thresholds. This spectroscopic progress provides new insight into the correlated electronic structure of Ce systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143090
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    High resolution in the soft x-ray range from a toroidal grating monochromator (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 2552-2557 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A resolving power, E/ΔE, of ≥13 000 has been achieved with the modified 6 m/160° toroidal grating monochromator (TGM) installed on Beam Line 8-1 at the Stanford Synchrotron Radiation Laboratory. The resolving power of the TGM was increased by replacing the entrance and exit slits with high-precision slits, masking the horizontal part (short radius) of the grating, and improving the TGM scanning mechanisms. To determine the performance of the monochromator, we measured the dependences of resolution and photon flux on the entrance- and exit-slit widths, the exit-slit position, and the masking of the grating. The monochromator resolution in the energy range of 25–65 eV was derived from photoionization measurements of extremely narrow core-excitation resonances in He and Ne. With 10-μm vertical entrance- and exit-slit widths and 32% mask opening of the grating, the monochromator has a resolution (full-width at half maximum) of 5.0±0.7 meV at a photon energy of 64.5 eV and a flux of 2×107 photons/s/100 mA. The results suggest a simple procedure for converting a TGM with moderate resolution into a high-resolution monochromator with a moderate reduction in photon flux due to masking the grating, beyond the reduction attributable to the slit widths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143866
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  • 5
    Electronic Resource
    Electronic Resource
    Angle-resolved inverse photoemission spectroscopy with longitudinally spin-polarized electrons (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2528-2533 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have built and tested a spin-polarized electron source based on photoemission from negative electron affinity GaAs(100). It provides 5–10 μA of longitudinally spin-polarized electrons in the energy range 5–20 eV. Following the design of Erdman and Zipf, the electron optics are simple and consist of only five elements. Their voltages are all proportional to each other and are linearly driven by one ramping voltage. The spin-polarized electrons are used for angle-resolved inverse photoemission measurements from magnetized sample surfaces. Our first results obtained from Ni(110) mounted on a horseshoe magnet agree well with the literature. From these measurements the degree of spin polarization is determined to be 35%±5%. We also checked the spin polarization using an absorbed-current spin detector in combination with a 90° cylindrical deflector.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141909
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Ballistic-electron emission microscopy study of the Au/Si(111)7×7 and Au/CaF2/Si(111)7×7 interfaces (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 2300-2302 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ballistic-electron emission microscopy (BEEM) has been performed on Au/n-Si(111)7×7 and Au/CaF2/n-Si(111)7×7 in UHV. In both cases, the topography of the Au surface is characterized by ≈2.5 A(ring) height terraces, stacked in several stages, with rounded shapes for Au/Si, and hexagonal shapes for Au/CaF2/Si. BEEM up to tip voltages of 8 V on Au/Si is not altering the ballistic transmissivity, in contrast to previous work on Au/Si interfaces which involved chemical preparations of the Si surfaces. The shape of the BEEM spectra on Au/CaF2/Si depends on spectral features of the density of states of the CaF2 thin film.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111650
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  • 7
    Electronic Resource
    Electronic Resource
    Resonant photoemission study ofK-derived valence-band states in K X C60 (1993)
    Springer
    The European physical journal 92 (1993), S. 347-351 
    Details
    ISSN: 1434-6036
    Keywords: 36.40.+d ; 74.75.+t ; 79.60.−i
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The electronic structure of K-doped C60 was investigated by photoemission (PE) and X-ray absorption near-edge structure (XANES) studies at the C-1s and K-2p thresholds. In addition, information on the local K-derived partial density of states in superconducting K3C60 was obtained by resonant PE at the K-2p 1/2 threshold. The experimental observations support a complete charge transfer from K to C60 and we clearly observe a finite density of states atE F . From resonant PE, occupied states with K-p, d character could be identified in the binding-energy region from 1.5 to 8 eV below, but not directly at the Fermi level. This partial-density-of-states structure agrees well with the results of our band-structure calculations based on the local-density approximation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01308753
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  • 8
    Electronic Resource
    Electronic Resource
    Resonant photoemission in highly localized versus weakly localized solids (1994)
    Springer
    The European physical journal 94 (1994), S. 1-2 
    Details
    ISSN: 1434-6036
    Keywords: 79.60.Cn ; 78.70.Dm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report on comparative study of angle-resolved photoelectron spectra of Ni metal and CeGd at theM III andN IV,V soft-x-ray absorption threshold, respectively. OnM III resonance, the valence-band photoemission (PE) intensity of Ni follows a cos2-behavior, while the intensity of the 6-eV satellite is independent of the angle of emission relative to the E-vector of the incoming beam. On the other hand, the 4f Ce PE signal behaves ∝ cos2 onN IV,V resonance. This clearly shows that the resonant enhancement of the 6-eV PE satellite of Ni is mainly caused by an incoherent Auger decay and cannot be described as a resonant PE process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01307645
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  • 9
    Electronic Resource
    Electronic Resource
    Scaling of the energy gap withT c in Bi2Sr2CaCu2O8+δ (1992)
    Springer
    The European physical journal 87 (1992), S. 271-273 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The results of a high-resolution photoemission study using synchrotron radiation of two single crystals of Bi2Sr2CaCu2O8+δ, with different critical temperaturesT c due to a variation in oxygen stoichiometry δ are reported. Within experimental accuracy, the energy gap 2Δ is found to scale withT c , amounting to a reduced gap parameter of 2Δ/k BTc≅7.4. Employing resonant photoemission at the O−2s and Cu−3p thresholds, two spectral peaks at binding energies of 180 meV and 320 meV were identified as predominantly O−2p-and Cu−3d 4s-derived states, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01309279
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  • 10
    Electronic Resource
    Electronic Resource
    Resonant photoemission at the 2p thresholds of Fe, Co, and Ni metal (1994)
    Springer
    The European physical journal 95 (1994), S. 9-12 
    Details
    ISSN: 1434-6036
    Keywords: 74.70.Vy ; 78.70.Dm ; 79.60.Eq
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Resonant photoemission studies have been performed at the 2p soft-x-ray absorption thresholds of Fe, Co, and Ni metal. At resonance, the photoelectron intensity exhibits a strong enhancement in the region of the two-hole satellites, which is shown, however, to be mostly due to an incoherent superposition of a photoemission signal with a more intense signal from anL 3 M 4,5 M 4,5 Coster-Kronig decay of the core-ionized state. The resonant enhancement of the valence-band photoemission satellite in Ni metal amounts to a factor of ≃12. In contrast, no photoemission satellites are observed for Fe and Co metal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01316837
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