Electron beam induced damage of NaNO3 single crystals: An energy, temperature, and quantum state resolved study

Electron beam induced damage of NaNO3 single crystals is examined using las er resonance enhanced multiphoton ionization detection of the neutral desor ption products, post-irradiation temperature-programmed desorption (TPD), s econdary electron emission microscopy (SEEM), and Auger electron spectrosco py (AES). The damage initially involves destruction of the nitrate group an d production of O (P-3(J)) and NO ((2)Pi) fragments with nonthermal energy distributions. Specifically, the O (P-3(J)) J State distribution measured a t 100 eV incident electron energy is 5:1.5:0.25 for J = 2:1:0, the NO ((2)P i) vibrational state distribution is 1:0.56:0.35:0.40:0.23 for nu = 0:1:2:3 :4, and the NO ((2)Pi(1/2,3/2)) rotational distribution has a high populati on of the upper ((2)Pi(3/2)) spin-orbit component. Production and desorptio n of these nonthermal fragments are dominated by the decay of {NO3-}*. At h igher electron fluences, thermalized NO, O-2, and NO2 are also produced and released, though the NO2 is a minor product. We suggest that the formation and desorption of thermalized NO and O-2 both involve NO2- defect states a nd unimolecular dissociation of NO3*. This is supported by the observation that the NO and O-2 yields have the same temperature dependence which is we ll described by the sum of two Maxwell-Boltzmann type equations with activa tion energies of 0.16 +/- 0.03 and 0.010 +/- 0.004 eV. O-2 gas is also rele ased in post-irradiation thermal cycling from 110 to 440 K with peaks at si milar to 260 and similar to 340 K. We associate the post-irradiation TPD of O-2 With reactions involving O atoms released during thermal decomposition of (NO2-... O) and ONOO-. The SEEM image shows damage features, and the AE S spectra indicate that the irradiated region is depleted in both nitrogen and oxygen relative to Na. The elemental composition shows Na2O as a final product of the NaNO3 radiation decomposition. The 100 eV electron beam dama ge cross section is at least similar to 10(-16) cm(2).