C. C. Bahr

Florida Institute of Technology

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M. J. Cardillo

Nokia (United States)

S. W. Robey

National Institute of Standards and Technology

D. A. Shirley

University of Tennessee at Knoxville

Z. Hussain

Hohai University

J. J. Barton

Vancouver Biotech (Canada)

A. vom Felde

Siemens (Germany)

D. A. Shirley

Pennsylvania State University

Julia W. P. Hsu

The University of Texas at Dallas

John Barton

University College Cork

L. E. Klebanoff

Sandia National Laboratories California

Cooperative Institutions

Lawrence Berkeley National Laboratory

University of California, Berkeley

Nokia (United States)

AT&T (United States)

Alcatel Lucent (Germany)

Stanford University

SLAC National Accelerator Laboratory

Stanford Synchrotron Radiation Lightsource

Technical University of Darmstadt

Lawrence Livermore National Laboratory

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Environmental Influences on K X-Rays from Highly Stripped Sulfur Ions Teavelng in Solids

IEEE Transactions on Nuclear Science (1981)

R. L. Watson A. Langenberg J. R. White R. A. Kenefick C. C. Bahr

As a fast heavy-ion passes through a material medium, it undergoes multiple collisions in which electrons are continuously lost and recaptured by the ion, and as a result, an equilibrium distribution of excited states is quickly established. The high density of electrons in a solid state environment enables these collisional excitation and decay processes to compete with x-ray and Auger decay. As a result, the widths of the x-ray lines exhibit a dependence on electron density due to collisional broadening. In addition, the potential of the ion is modified by the polarization of loosely bound electrons of the medium. In effect, these electrons act to screen the ion potential, thereby causing the core electron binding energies of the ion to decrease. As a result of this "dynamic screening" effect, the x-ray transition energies inside the medium differ from those in vacuum.

Auger effect

10.1109/tns.1981.4331335

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Citations (2)

Carrier excitation by hyperthermal Xe collisions at a Si(111): As surface

Surface Science Letters (1992)

J.W.P. Hsu C. C. Bahr A. vom Felde D.R. Miller M.J. Cardillo

10.1016/0167-2584(92)90085-j

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Energy shifts ofKαx rays from highly stripped sulfur ions traveling in solids

Physical review. A, General physics (1981)

R. L. Watson A. Langenberg R. A. Kenefick C. C. Bahr J. R. White

The energies and intensities of the $2^{3}P_{1}\ensuremath{\rightarrow}1^{1}S_{0}$, and $2^{1}P_{1}\ensuremath{\rightarrow}1^{1}S_{0}$ transitions in He-like sulfur ions, and of the $2^{2}P\ensuremath{\rightarrow}1^{2}S$ transition in H-like sulfur ions have been studied as a function of the thickness and electron density of the solid through which the ions travel. The thickness dependence of the x-ray intensities was analyzed in terms of a three-component model description of $K$-shell vacancy production and decay. Cross sections for electron excitation or ionization and capture deduced from this analysis were used to establish the energies of the x-ray peaks for complete emission in vacuum (i.e., outside the target). Energy shifts were obtained by comparing the peak energies for emission in thick targets to those for emission in vacuum. The results show that the energy shifts increase approximately linearly with the square root of the valence electron density of the target and are in good agreement with theoretical expectations.

Electron capture

Valence electron

10.1103/physreva.23.2471

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Citations (11)

Valence photoelectron satellites of neon

Physical review. A, General physics (1985)

Philip A. Heimann C. M. Truesdale H. G. Kerkhoff D. W. Lindle T. A. Ferrett

Synchrotron radiation was directed at neon gas, creating ${\mathrm{Ne}}^{+}$ ions in ``satellite'' states characterized by the configurations 1${s}^{2}$2${s}^{2}$2${p}^{4}$nl, in addition to the main-line final states: 2${s}^{\mathrm{\ensuremath{-}}1}$ and 2${p}^{\mathrm{\ensuremath{-}}1}$. Satellite features appearing in the photoelectron spectrum were studied in the near-threshold region with photon energies from 55.2 to 99.7 eV. For three of the satellite peaks, the angular-distribution-asymmetry parameter ${\ensuremath{\beta}}_{i}$ varies with kinetic energy in much the same way as the asymmetry parameter of the 2p line. None of the satellites have a ${\ensuremath{\beta}}_{i}$ like that of the 2s line. All the satellite partial cross sections ${\ensuremath{\sigma}}_{i}$ have a kinetic-energy dependence similar to the partial cross section of the 2p main line. However, the ${\ensuremath{\sigma}}_{i}$ curves are not identical, and some deviation from the 2p intensity behavior is observed. These ${\ensuremath{\beta}}_{i}$ and ${\ensuremath{\sigma}}_{i}$ results are used to confirm the previous assignments of the satellite final states in neon and to consider, in general, the energy-dependent behavior of satellites near threshold.

Line (geometry)

Sigma

10.1103/physreva.31.2260

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Citations (31)

Surface structure determination with ARPEFS. [C(2x2)S/Ni(100); p(2x2)S/Cu(100); c(2x2)S/Ni(110)]

J. J. Barton S. W. Robey C. C. Bahr D. A. Shirley

We describe a method of surface structure determination based on oscillations in core-level photoemission intensity - Angle-Resolved Photoemission Extended Fine Structure - with particular emphasis on the use of Fourier transformation. Qualitative comparisons of Fourier power spectra reveal adsorption sites and shortcomings in theoretical calculations; quantitative backtransformation analysis allows accurate bond lengths and bond angles to be determined. Examples are drawn from these similar atomic adsorption systems: c(2x2)S/Ni(100), p(2x2)S/Cu(100) and c(2x2)S/Ni(110).

Intensity

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Competition between desorption and diffusion at a GaAs(110) surface

Chemical Physics Letters (1993)

A. vom Felde C. C. Bahr M. J. Cardillo

Surface diffusion

Molecular beam

10.1016/0009-2614(93)85371-t

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Citations (8)

Surface Structure Determination with ARPEFS

Springer series in surface sciences (1985)

J. J. Barton S. W. Robey C. C. Bahr D. A. Shirley

Intensity

10.1007/978-3-642-82493-7_31

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Citations (3)

REPLY TO THE COMMENT ON ""GEOMETRY OF (2X2)S/CU(001) DETERMINED WITH USE OF ANGLE-RESOLVED PHOTOEMISSION EXTENDED FINE STRUCTURE""

D. A. Shirley L. J. Terminello C. C. Bahr

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Direct determination of surface structures from photoelectron diffraction

John Barton C. C. Bahr Z. Hussain S. W. Robey L. E. Klebanoff

Angle‐resolved photoemission extended fine structure (ARPEFS) is induced by interference between primary and elastically scattered photoelectron waves originating from an adsorbate core level on an ordered surface. Analysis by procedures analogous to those used in surface EXAFS yields absolute surface structures directly. ARPEFS appears capable of yielding bond distances with the same accuracy as EXAFS, and accurate bond angles. The coordination number is unambiguous with ARPEFS. Experiments have been performed with c(2×2)S/Ni(001), along [001] and [011], and p(2×2)S/Cu(001), along [011]. The differential photoelectron cross section in the [011] direction, for example, is modulated by ±50% in ARPEFS, in contrast to the ±2–3% effects observed in surface EXAFS. Single‐scattering theory yields a simple dependence of χ(k)=[I(k)−I0(k)]/I0(k) on the angles αj=cos−1(p,pj), βj=cos−1(e,pj), and γ=cos−1 (e,p) relating the primary wave propagation direction p, the direction pj of scattering off atom j, and the photo...

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Surface effects on carrier dynamics: photoconductivity studies on Si (111)

Journal of Applied Physics (1992)

Julia W. P. Hsu C. C. Bahr A. vom Felde S. W. Downey G. S. Higashi

We correlate photoconductivity with surface characterization in order to probe the influence of different surface properties of Si (111) on electron-hole dynamics. Photoconductivity data show that the carrier recombination is influenced strongly by surface structure and chemistry as well as by trace imperfections which are undetectable by conventional surface characterization techniques. Results on the Si(111):As (1×1) surface indicate carrier recombination at this surface is negligible, in contrast to the (7×7) reconstructed surface, where surface recombination is fast, with a surface recombination velocity measured to be ≥2×106 cm/s. We also investigate the effect of sputter induced disorder and compare our finding with results from other techniques. Combining our results and the present understanding of the (7×7) electronic structure, we estimate the carrier capture cross section for dangling bonds to be ∼10−15 cm2.

Photoconductivity

Dangling bond

Characterization

Carrier lifetime

Surface States

Surface reconstruction

10.1063/1.350597

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Citations (12)