Beitrag zur Theorie des Durchganges langsamer Elektronen durch Gase

Faxén, H.; Holtsmark, J.

doi:10.1007/bf01343053

Cited by 162 publications

(19 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…4͒ for both the nanoparticles in the as-prepared state and after plasma cleaning indicates a sharp minimum in backscattering amplitude at k Ϸ 60/ nm that is known in literature as Ramsauer-Townsend effect. 21 The reduction in the scattering amplitude over a small region in k space exists for several elements with atomic numbers near 80, such as Pt ͑Z =78͒ ͑Ref. 22͒, but for most elements ͑e.g., Fe͒ the scattering amplitude varies slowly as a function of k. Therefore, the clear enhancement of this feature in the EXAFS of the FePt nanoparticles with respect to the EXAFS in the FePt bulk material gives evidence for Pt enrichment around the Pt absorber atoms, i.e., an inhomogeneous composition within the nanoparticles.…”

mentioning

confidence: 99%

Lattice expansion in nonoxidized FePt nanoparticles: X-ray absorption measurements

et al. 2008

View full text Add to dashboard Cite

mentioning

confidence: 99%

Lattice expansion in nonoxidized FePt nanoparticles: X-ray absorption measurements

et al. 2008

View full text Add to dashboard Cite

“…Since only two partial wave states are involved in the collision process the scattering yield and angular distributions have a simple interpretation in terms of a theoretical model. Collisions of atoms is a classic discipline of quantum mechanics [1,2]. With the advent of laser cooling [3], confining and cooling various atomic species to submillikelvin temperatures became possible and gave rise to a wealth of experiments in which quantum effects in collisions at very low energiescold collisions -were observed [4].…”

mentioning

confidence: 99%

Imaging ofsanddPartial-Wave Interference in Quantum Scattering of Identical Bosonic Atoms

et al. 2004

View full text Add to dashboard Cite

We report on the direct imaging of s and d partial-wave interference in cold collisions of atoms. Two ultracold clouds of 87 Rb atoms were accelerated by magnetic fields to collide at energies near a d-wave shape resonance. The resulting halos of scattered particles were imaged using laser absorption. By scanning across the resonance we observed a marked evolution of the scattering patterns due to the energy dependent phase shifts for the interfering s and d waves. Since only two partial wave states are involved in the collision process the scattering yield and angular distributions have a simple interpretation in terms of a theoretical model. 03.65.Nk, 32.80.Pj, 39.25.+k Collisions of atoms is a classic discipline of quantum mechanics [1,2]. With the advent of laser cooling [3], confining and cooling various atomic species to submillikelvin temperatures became possible and gave rise to a wealth of experiments in which quantum effects in collisions at very low energiescold collisions -were observed [4]. Knowledge about cold collision properties paved the way for exciting new developments in experimental atomic physics. It played a crucial role in achieving Bose-Einstein condensation [5] and Fermi degeneracy [6] in dilute atomic vapors by mediating thermalization during evaporative cooling and accounting for stability [7]. For atoms at temperatures associated with the quantum degenerate regime the essential interaction properties are determined by a single atomic parameter, the scattering length, because all elastic scattering has an isotropic (s-wave) nature at such low energies. The scattering length may exhibit a pronounced dependency on external magnetic fields giving rise to FIG. 1: (Color online) Illustration of the process of using absorption imaging for the detection of scattered particles. We present the case of pure d-wave scattering occurring at the origin for particles coming in along the z-axis. Scattered particles will be situated on an expanding sphere and distributed according the d-wave angular emission pattern |f (θ)| 2 . Absorption imaging along the x-axis projects this distribution onto the yz-plane. [9,10,11,12,13].To date, most experiments on cold collisions of atoms have been carried out using magneto-optical traps (MOTs) or magnetic traps which suffer from the disadvantages that no collision axis is singled out or the collision energy cannot be varied over a wide range [4,14]. If no fixed collision axis is present, anisotropic scattering, as occurs for collision energies above the s-wave regime, will be obscured by spatial averaging. One solution to this problem was provided in the "juggling" MOT experiment [15], where a cloud of cesium atoms was laser cooled to 3 µK and ejected vertically from a trap to collide with a previously launched cloud at energies up 160 µK. Scattered atoms were detected using a spectroscopic technique revealing interference between s and p partial waves. In experiments on BECs, a collision axis was also selected using Bragg scattering to accelerate part of t...

show abstract

“…If l in ½ l e , the interaction is an elastic scattering. The non-relativistic differential cross-section of elastic scattering is calculated using the partial wave expansion method 8 and the values of the IMFP are taken from the literature (TPP-2 9 ). Each elastically reflected electron trajectory is followed inside the solid until the electron leaves the sample.…”

Section: E R W I S Ementioning

confidence: 99%

Determination of yield ratios of elastically backscattered electrons for deriving inelastic mean free paths in solids

Varga

Kövér

Tóth

et al. 2000

Surf. Interface Anal.

View full text Add to dashboard Cite

Intensity ratios of electrons backscattered elastically from thick, amorphous Si, polycrystalline Ag and Au, as well as various (vacuum evaporated, electrodeposited layers and metallic sheets) polycrystalline Ni samples, were measured using high energy resolution and two different experimental geometries (0°and 50°primary and 50°and 0°scattered beam angles relative to the surface normal, respectively) in the range of 1-5 keV primary electron beam energy. The elastic yield ratios obtained experimentally are compared to the results computed by Monte Carlo simulations using different algorithms and different sets of parameters.In the case of measured elastic yield ratios Si/Ni, Ag/Ni and Au/Ni, systematic differences were observed between the respective values obtained for two experimental geometries, whereas each Monte Carlo calculation predicted similar ratios for the different geometries. For the Si/Ag, Si/Au and Ag/Au elastic yield ratios, however, good agreement is observed between experiment and calculation, resulting in similar ratios for each geometry.As a conclusion to our study, we suggest that when using a polycrystalline Ni standard reference sample for measuring elastic yield ratios the homogeneity of the sample should be ensured. Our results confirm the applicability of elastic peak electron spectroscopy in the case of these solids for deriving IMFP values, i.e. no significant role of surface effects on the elastic yield ratios can be identified in the primary beam energy range studied.

show abstract

Beitrag zur Theorie des Durchganges langsamer Elektronen durch Gase

Cited by 162 publications

References 0 publications

Lattice expansion in nonoxidized FePt nanoparticles: X-ray absorption measurements

Lattice expansion in nonoxidized FePt nanoparticles: X-ray absorption measurements

Imaging ofsanddPartial-Wave Interference in Quantum Scattering of Identical Bosonic Atoms

Determination of yield ratios of elastically backscattered electrons for deriving inelastic mean free paths in solids

Contact Info

Product

Resources

About