Mark R.A. Shegelski

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We consider the motion of a cylinder with the same mass and size as a curling rock, but with a very different contact geometry. Whereas the contact area of a curling rock is a thin annulus having a radius of 6.25 cm and width of about 4 mm, the contact area of the cylinder investigated takes the form of several linear segments regularly spaced around the(More)
In low energy electron point source (LEEPS) microscopy, electrons emerge from a point source, propagate as spherical waves, and arrive at a screen. Some electrons scatter off an object, i.e. a cluster of atoms, placed between the source and the screen; others arrive at the screen without scattering. The interference pattern on the screen, an electron(More)
The theory of the low energy electron point source (LEEPS) microscope is presented in matrix form to account for multiple scattering. An iterative method is used to solve the matrix equation for the structure factor. An algorithm is developed for the storage and use of only the dominant elements of the structure matrix; this allows for the study of(More)
We compare the exact tunneling time with the quasi-classical tunneling time for idealized potentials. We examine three one-dimensional cases where the potential is chosen to have a simple form. In each case, the exact tunneling time and the quasi-classical time differ significantly. In one case, the two differ in magnitude by a factor of about ten. In(More)
Depth resolution in the reconstruction of in-line holograms taken with the low-energy electron point source (LEEPS) microscope is improved by employing, on the basis of a Kirchho!}Helmholtz-type reconstruction integral, (i) a to-mographic approach, sampling several screen positions, and (ii) a weighted energy averaging. The improved reconstructions exhibit(More)
We report a new method that gives atomic resolution in the reconstruction of simulated holograms in theoretical low energy electron point source (LEEPS) microscopy, and that uses a screen size that is commensurate with screen sizes used in experimental LEEPS. The method exploits the spherical symmetry in the electron waves emerging from the source. We(More)
We generate simulated holograms for low energy electron point source (LEEPS) microscopy. For a given object (atomic cluster) we construct a number of different holograms by varying the position or the orientation of the object relative to the screen. We then compare the three-dimensional structures of the reconstructions obtained from these holograms using(More)
In theoretical low energy electron point source microscopy, simulated holograms are made and used to reconstruct atomic clusters. In previous investigations, simple test clusters were used for convenience. In this paper we explore more realistic structures composed of a single type of atom such as diamond, graphite and Buckminsterfullerene--all of which(More)
The theory of the low-energy electron point source (LEEPS) microscope is reformulated in matrix form to readily account for multiple scattering. An algorithm is developed for the storage of the structure matrix and an iterative method is used to solve the matrix equation for the structure factor. Examples of small and large clusters of atoms are given to(More)
We show that rapidly rotating cylinders sliding on smooth surfaces can exhibit novel trajectories. The lateral deflection can be as large as the net displacement in the initial direction of motion. With a large enough initial angular speed, the cylinder can trace out a spiral trajectory having a large number of loops. An exact analytical result for large(More)