14.1 VLEED: Multibeam Resonant Diffraction
265
Fig. 14.1 SPB multi-reflection produces the VLEED fine structures. Part of the amplitude of the
incident beam is diffracted into the direction of the measured beam and part of the beam into the
preemergent beam. The amplitude in the preemergent beam is turned back by the SPB. Part of this
amplitude diffracts back into the direction of the preemergent beam. The measured intensity sums
the squares of the repeatedly amplitudes. Reprinted with permission from [3]
Fig. 14.2 A LEED diffraction pattern of a room temperature O–Cu(001) surface after 480 L
showing a well ordered (
√
2 × 2
√
2) superstructure. The (00) pattern intensity-energy (I-E) profiles
in the 6.0–16.0 eV range form the VLEED spectroscopy [3, 5]
is diffracted into the specular direction and then scattered into high-order beams in all
directions, depending on the incident conditions. If the high-order beams do not have
sufficient energy perpendicular to the surface to escape from the SPB confinement
they are totally internally reflected. They can then be re-scattered by the substrate
back into the specular direction.