Surface Helium-3 Spin Echo (HeSE) spectroscopy enables the studies of ultra-fast atomic-scale dynamics at surfaces. It is a Fourier transform spectroscopy which is based on atom scattering, and measures time-correlations at surfaces with atomic resolution, albeit in reciprocal space. The conceptual experiment follows from neutron spin-echo spectroscopy, which allows to study ultra-fast dynamics of the bulk. A realisation of the concept to helium scattering was achieved by de Kieviet et. al., and later on, an application to surface dynamics was developed in Cambridge UK.[1, 3]
The experimental setup includes a source producing a helium-3 molecular beam which is then focused and polarised, and undergoes a series of magnetic manipulations prior and post scattering from the surface. The change in the spin polarisation of the helium atoms due to the scattering from the surface is then measured using a sequence of a magnetic analyser and a magnetic-trap based ionising detector. The current practical temporal window of the Cambridge instrument is between sub-picosecond to about 2 nanosecond, with further extension anticipated in the near future.
With incomparable surface sensitivity and energy resolution of 3 microelectron volts, HeSE is best known for the unique information it provides on surfaces, in particular:
- atomic-scale friction.
- rate of molecular transport.
- energy landscapes.
- inter-adsorbate interactions at the low coverage and/or elevated temperature regime.
- lifetimes of surface phonons.
The information highlighted above is available in (nearly) any HeSE measurement, and is of high scientific value in its own right.
 AP Jardine et al. Helium-3 spin-echo: Principles and application to dynamics at
surfaces”. In: Progress in Surface Science 84.11-12 (2009), pp. 323-379.
 M DeKieviet et al. Surface science using molecular beam spin echo”. In: Surface
science 377 (1997), pp. 1112-1117
 G Alexandrowicz and AP Jardine. Helium spin-echo spectroscopy: studying surface dynamics with ultra-high-energy resolution”. In: Journal of Physics: Condensed Matter 19.30 (2007), p. 305001