Electron Beam Induced Damage of NaNO3 Single Crystals: An Energy, Temperature, and Quantum State Resolved Study

Electron beam induced damage of NaNO 3 single crystals is examined using laser resonance enhanced multiphoton ionization detection of the neutral desorption products, post-irradiation temperature-programmed desorption (TPD), secondary electron emission microscopy (SEEM), and Auger electron spectroscopy (AES). The damage initially involves destruction of the nitrate group and production of O ( 3 P J ) and NO ( 2 Π) fragments with nonthermal energy distributions. Specifically, the O ( 3 P J ) J state distribution measured at 100 eV incident electron energy is 5:1.5:0.25 for J = 2:1:0, the NO ( 2 Π) vibrational state distribution is 1:0.56:0.35:0.40:0.23 for ν = 0:1:2:3:4, and the NO ( 2 Π 1/2,3/2 ) rotational distribution has a high population of the upper ( 2 Π 3/2 ) spin−orbit component. Production and desorption of these nonthermal fragments are dominated by the decay of {NO 3 - }*. At higher electron fluences, thermalized NO, O 2, and NO 2 are also produced and released, though the NO 2 is a minor product. We suggest that the formation and desorption of thermalized NO and O 2 both involve NO 2 - defect states and unimolecular dissociation of NO 3 *. This is supported by the observation that the NO and O 2 yields have the same temperature dependence which is well described by the sum of two Maxwell−Boltzmann type equations with activation energies of 0.16 ± 0.03 and 0.010 ± 0.004 eV. O 2 gas is also released in post-irradiation thermal cycling from 110 to 440 K with peaks at ∼260 and ∼340 K. We associate the post-irradiation TPD of O 2 with reactions involving O atoms released during thermal decomposition of {NO 2 - ···O} and ONOO - . The SEEM image shows damage features, and the AES spectra indicate that the irradiated region is depleted in both nitrogen and oxygen relative to Na. The elemental composition shows Na 2 O as a final product of the NaNO 3 radiation decomposition. The 100 eV electron beam damage cross section is at least ∼10 -16 cm 2 .