Electron-stimulated desorption of iodine atoms from KI(100): an energy- and temperature-dependent study

We have studied the electron-stimulated desorption (ESD) of neutral atomic iodine from single crystals of KI(100) using time-of-flight laser-resonance -enhanced multiphoton ionization spectroscopy and quadrupole mass spectrome try. The measured iodine velocity distributions have thermal and non-therma l components. The yield of the thermal component increases with increasing substrate temperature, whereas the yield of the non-thermal component decre ases slightly with temperature. The ESD rate for the thermal component decr eases with increasing pulse width, unlike the rate for the non-thermal comp onent, which is independent of pulse width. Measurements of ESD yields vers us incident electron energy indicate a threshold of similar to 5.5 eV. The data collectively indicate that ESD of KI involves exciton decay at the sur face. The temperature and pulse-width dependencies of the thermal component are consistent with decay of bulk self-trapped excitons, thermally assiste d H-center diffusion and trapping at metastable defects. (C) 2000 Elsevier Science B.V. All rights reserved.