Empirical Determination of Scattering Matrices from Magnetic Molecular Interferometry for Gas-Surface Collisions.

The rotational orientation dependence of H scattering into different diffraction channels on a Cu(511) surface is studied using a magnetic manipulation interferometry technique. For some channels, markedly different signals are measured, whereas for others, they are more similar. The data are analyzed to obtain scattering matrices, which quantify how the amplitude and phase of the wave function change during the gas-surface collision and are extremely sensitive to the underlying potential.

Neutral beam microscopy with a reciprocal space approach using magnetic beam spin encoding.

The emerging technique of neutral beam microscopy offers a non-perturbative way of imaging surfaces of various materials which cannot be studied using conventional microscopes. Current neutral beam microscopes use either diffractive focusing or pin-hole scanning to achieve spatial resolution, and are characterised by a strong dependence of the imaging time on the required resolution. In this work we introduce an alternative method for achieving spatial resolution with neutral atom beams which is based on manipulating the magnetic moments of the beam particles in a gradient field, and is characterised by a much weaker dependence of the imaging time on the image resolution.

Temperature dependent stereodynamics in surface scattering measured through subtle changes in the molecular wave function.

A magnetically manipulated molecular beam technique is used to change the rotational orientation of H molecules which collide with a stepped Cu(511) surface and explore how the polarisation dependence of molecules scattering into the specular channel changes as a function of surface temperature. At all temperatures, H molecules that are rotating like cartwheels are more likely to be scattered into the specular channel than those that are rotating like helicopters. Furthermore, the scattered molecules are more likely to be rotating like cartwheels, regardless of their state before the collision.

Multiple echoes in beam spin-echo spectroscopy and their effect on measurements of ultra-fast dynamics.

Helium (He) spin-echo is a powerful experimental technique used to probe ultra-fast atomic scale surface dynamics. The analysis of these measurements is typically performed assuming there is only a single spin-echo condition, expected to produce a constant signal for pure elastic scattering, a monotonically decaying signal for quasi-elastic scattering and oscillations from inelastic scattering events. In the present work, we show that there are in fact four spin-echoes which must be correctly accounted for, and that even in the case of elastic scattering these additional echoes lead to oscillations which could mistakenly be interpreted as being due to inelastic scattering.