Photon-stimulated desorption of Na atoms from NaCl following core-level excitation

Desorption of neutral sodium atoms from the (100) surface of single-crystal NaCl has been observed following Cl(ls) core-level excitation with synchrotron radiation. The yield of photon-stimulated desorption (PSD) was measured as a function of X-ray energy and for sample temperatures from 300 to 700 K. It was found that the bulk NaCl crystal showed significant desorption at and above the ClK-edge, and that the dependence of the Na atom yield on X-ray energy has the same threshold and gross features as the total electron yield spectrum. However, PSD from a 20 Å thick NaCl layer deposited on Si(100) could not be detected. We propose that the observed neutral PSD of alkali halides is associated with long range diffusion of highly mobile “hot valence holes” created predominantly by secondary electrons from Auger-decay cascades following the primary excitation.