Der Einfluß tiefer Temperaturen auf die Strahlenschädigung von organischen Kristallen durch 100 keV-Elektronen / The Influence of Very Low Temperature on the Radiation Damage of Organic Crystals Irradiated by 100 keV-Electrons

The radiation damage of electron irradiated organic compounds (paraffin, tetracene) was investigated in the temperature range 300 - 4 K. The radiation damage was measured by the decrease of diffraction intensities or the contrast of extinction contours. The damage of the crystals at 4 K required considerable higher electron doses than at 300 K. This result is explained as follows: The total radiation damage proceeds by two steps: 1) By primary radiation damage - excitation of energy levels with subsequent dissociation - which is almost temperature independent, 2) by secondary radiation damage - diffusion of molecular fragments - which decreases strongly with decreasing temperature.