Radiation damage is a major limiting factor in obtaining high resolution images in cryo-electron microscopy. Quantifying and understanding those radiation damages are considerable challenges. While it seems commonly admitted that the major part of the damages comes from radiolysis, local charging within the ice or the sample has been mentioned several time as a source of damage.
Due to the isolator behavior of frozen H2O, samples undergo electrostatic charging. While it has never been directly measured, this charging effect is often observable in cryo-electron microscopy in the form of beam deflection or Coulomb-explosion (as shown in Figure 1).
Aranova et al. showed that Electron Energy Loss Spectroscopy (EELS) could be used to measure the production of H2 and O2 associated to “bubbles” often observed in cryo-EM when damages start to occurs . A very interesting finding in their report is that no bubbles were observed in pure frozen water (without sample in it). One possible explanation is that radicals recombine more quickly in H2O than in frozen hydrated specimens in a Transmission Electron Microsocope.
During this presentation, we will study with mono-chromated EELS the effects of the incident electron beam on frozen H2O as well as on frozen aqueous samples. Both the radiolysis and the electrostatic aspects of the beam/matter interaction can be measured with EELS using Kramer-Kronig formula (through dielectric formalism) and Valence EELS (to look at chemical structure changes and bubbles production). We will show that depending on the type of electron illumination (STEM or TEM), the nature and intensity of those damages can vary. We will, then, look at several possible solutions to reduce such damages.
 C. Laffon, S. Lacombe, F. Bournel, P. Parent., 2006. Radiation effects in water ice:a near-edge X-ray absorption fine structure study. Journal of Chemical Physics 125 (20), 204714.
 Egerton R.F. 2014. Choice of operating voltage for a transmission electron microscope. Ultramicroscopy 145, 85-93.
M.A. Aronova, A.A. Sousa, R.D. Leapman 2011. EELS characterization of radiolytic products in frozen samples. Micron 42, 252-256
To cite this abstract:Alan Maigne, Matthias Wolf; EELS analysis of the interaction betweeen frozen acqueous samples and incident electrons in TEM. The 16th European Microscopy Congress, Lyon, France. https://emc-proceedings.com/abstract/eels-analysis-of-the-interaction-betweeen-frozen-acqueous-samples-and-incident-electrons-in-tem/. Accessed: December 5, 2022
EMC Abstracts - https://emc-proceedings.com/abstract/eels-analysis-of-the-interaction-betweeen-frozen-acqueous-samples-and-incident-electrons-in-tem/