Radiation damage in electron microscopy of organic materials: effect of low temperatures

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Abstract
As measured by the life‐time of their electron diffraction patterns, the radiation sensitivity of anthracene and coronene at 500 kV is reduced by a factor of three to four at liquid helium temperature in comparison to room temperature. For l‐valine the ratio is about 1·8 but there is a wide variation in the results, possibly due to differences in crystal thickness. The end‐dose at 20°K for valine is equivalent to 13 electrons/Å2; for anthracene and coronene it is about 600 electrons/Å2 at room temperature. The variation of end‐dose with temperature shows that at least two mechanisms must be involved in damage to such compounds, possibly concerning the breaking of intermolecular and intramolecular bonds, respectively.