In this presentation, we show that x-rays can be used to characterize the elemental and chemical state of just one atom. Using a specialized tip as a detector, x-ray excited currents generated from an iron and a terbium atom coordinated to organic ligands are detected. The fingerprints of a single atom, the L2,3 and M4,5 absorption edge signals for iron and terbium respectively, are clearly observed in x-ray absorption spectra. X-ray excited resonance tunnelling is dominant for the iron atom. The x-ray signal can be sensed only when the tip detector is located directly above the atom in extreme proximity, which confirms atomically localized detection in the tunnelling regime. Our work connects synchrotron x-rays with a quantum tunnelling process and opens future x-rays experiments for simultaneous characterizations of elemental, and chemical properties of materials at the ultimate single atom limit
Volker Rose (Mon,) studied this question.