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

Well-shaped single crystals of nitrogen were prepared on a carbon film by adiabatic expansion of liquid nitrogen. The crystal structure was investigated by electron diffraction and high-resolution imaging using a helium-cooled, superconducting electron microscope. The crystals turned out to be α-nitrogen with face centred cubic structure as described in literature. Radiation damage results in a loss of crystallinity and mass. The mass loss was determined at different acceleration voltages. Twenty-three electrons with 160 keV energy were necessary to release one nitrogen molecule. Within a margin of error this number decreases proportionally to decreasing electron energy.