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.

Molecular spin echoes; multiple magnetic coherences in molecule surface scattering experiments.

In this paper we demonstrate that a molecular beam of hydrogen molecules can be magnetically manipulated to produce multiple coherences in the molecular interference pattern. Unlike spin 1/2 magnetic beam experiments, i.e.

Setting benchmarks for modelling gas-surface interactions using coherent control of rotational orientation states.

The coherent evolution of a molecular quantum state during a molecule-surface collision is a detailed descriptor of the interaction potential which was so far inaccessible to measurements. Here we use a magnetically controlled molecular beam technique to study the collision of rotationally oriented ground state hydrogen molecules with a lithium fluoride surface. The coherent control nature of the technique allows us to measure the changes in the complex amplitudes of the rotational projection quantum states, and express them using a scattering matrix formalism.

A general method for controlling and resolving rotational orientation of molecules in molecule-surface collisions.

The outcome of molecule-surface collisions can be modified by pre-aligning the molecule; however, experiments accomplishing this are rare because of the difficulty of preparing molecules in aligned quantum states. Here we present a general solution to this problem based on magnetic manipulation of the rotational magnetic moment of the incident molecule. We apply the technique to the scattering of H from flat and stepped copper surfaces.

Probing the Superfluid Response of para-Hydrogen with a Sulfur Dioxide Dopant.

We recently presented the first attempt at using an asymmetric top molecule (para-water) to probe the superfluidity of nanoclusters (of para-hydrogen) [ Zeng , T. ; Li , H. ; Roy , P.