ELECTRON-STIMULATED NEUTRAL AND ION EMISSION FROM SINGLE-CRYSTAL NANO3

Quadrupole mass spectrometry of the neutral products accompanying irradiation of single crystal NaNO3 with a pulsed beam of 1-3 keV electrons shows intense NO and O-2 emissions and smaller amounts of Na and NO2. Time-of-flight and intensity measurements as a function of pulse width and temperature are consistent with NO emission via a thermally assisted, electronic emission mechanism. The activation energy for the thermally assisted process is about 0.11 eV-similar to the excitation energies for internal vibrational modes of the NO3- anion. The emission of neutral O-2 involves fairly complex reactions with dissociation products and is also thermally assisted at temperatures above 380 K. Mass-selected ion emission measurements indicate copious H+ emission, where the temperature dependence of the H+ intensity is similar to that of NO. We propose that H+ emission is limited by the density of appropriate surface defect sites, and that these sites are directly related to NO3- dissociation.