Solid nitrogen: electron microscopy and beam damage quantification at 4 K

Well-shaped single crystals of nitrogen were prepared on a carbon film by a diabatic expansion of liquid nitrogen. The crystal structure was investigat ed by electron diffraction and high-resolution imaging using a helium-coole d, superconducting electron microscope. The crystals turned out to be a-nit rogen with face centred cubic structure as described in literature. Radiati on damage results in a loss of crystallinity and mass. The mass loss was de termined at different acceleration voltages. Twenty-three electrons with 16 0 keV energy were necessary to release one nitrogen molecule. Within a marg in of error this number decreases proportionally to decreasing electron ene rgy. (C) 1999 Elsevier Science B.V. All rights reserved.