Researchers from University of Texas at Arlington, the University of Western Australia (Crawley, Australia), Northeastern University (Boston, Massachusetts) and Kazan State University (Russian Federation) have devised an efficient way to probe the surface of materials using positrons. [Mukherjee et al., Phys. Rev. Lett., DOI: 10.1103/PhysRevLett.104.247403]
A slow positron can be trapped at a surface and then annihilates. One can analyze the distribution of photons and electrons that are caused by this annihilation to gain unique surface information.
The present investigation reveals, for the first time, a single step quantum mechanism to stick a positron on a metallic surface - the so-called "Auger-Mediated Sticking” (AMS).
The physics of the AMS is closely related to the Auger Neutralization, which has been studied for decades in various fields.
However, most of the previous work describes collisions of slow ions with solids, while the present study involves the trapping of slow positron on metallic surfaces. The quantum mechanical nature of the AMS follows from the fact that the positron is much lighter than the ions. In this work, the authors provide a robust estimate of positron sticking probability.
The fact that the AMS has an efficiency exceeding 10% at positron energies of about 1 eV proves that it will be possible to use low energy positron beams to selectively probe the surfaces of fragile systems such as nano-particles and biomaterials.