Landolt-Börnstein - Group III Condensed Matter Kinematic focussing


This chapter provides information on kinematic focusing of inelastic scattering. For in-plane one-phonon scattering, the kinematic relations can be summarized as follows: the contribution of the j-th phonon branch is proportional to δ(Δω-ωk ||, j)), where Δω is related to Δk || by the scan curve. For the surface-projected bulk phonon branches, the index j stands for the quasi-continuous perpendicular wave number q z and a discrete band index, such as longitudinal acoustic (LA). In this case the δ-functions for neighboring values of q z overlap, giving a continuous distribution of the scattered one-phonon intensity. On the other hand, a surface phonon branch, such as the Rayleigh branch, corresponds to a discrete value of j-th and makes a δ-like contribution to the scattered intensity, with integrated strength diverges when the scan curve osculates the phonon dispersion curve. This condition is known as kinematic focusing. Many observations of kinematic focusing have been reported. The effect is not restricted to the surface phonon branches and can lead to enhancements in the continuum spectrum. The extension to out-of-plane scattering has been discussed for the use of kinematic focusing to measure phonon dispersion relations throughout the Brillouin zone without a TOF apparatus.

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Title Kinematic focussing
Book Title
Interaction of Charged Particles and Atoms with Surfaces
In Kinematics
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Chapter DOI
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Landolt-Börnstein - Group III Condensed Matter
  • G. Chiarotti
  • Authors
  • V. Celli
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