Eugen Illenberger

Physical and Theoretical Chemistry, Freie Universitaet Berlin

We report on chemical reactions initiated by free electrons at energies below the level of electronic excitation for the respective molecules (< 3 eV). Most photochemically initiated reactions involve excited species where an electron is promoted, e. g., from the highest occupied molecular orbital (MO) to the lowest unoccupied orbital (LUMO) associated with an energy supply in the range of several eV. In contrast, the addition of an excess electron into the LUMO (generating a molecular negative ion) is often possible at very low energies, i. e., below the threshold for electronic excitation and often close to zero eV. The negative ion resonance thereby formed can be very reactive in that it dissociates by selective bond cleavage at remarkably high cross sections.

We have applied these peculiar properties of dissociative electron attachment (DEA) to explore some interesting and fascinating problems in different areas of fundamental and applied science.
We demonstrate
• that DEA is a very convenient method to study charge and energy distributions in unimolecular reactions [1]
• the potential of slow electrons as a soft and effective tool for surface modification [2], and
• the role of sub-ionisation electrons to the problem of radiation damage and the operation of radio¬sensitisers used in radiotherapy [3].
 

References
[1] Energy Balance in Dissociative Attachment to C2F5I
Judith Langer, Stefan Matejcik, Eugen Illenberger
Phys. Chem. Chem. Phys. 4 (2002) 5105.
[2] Complete Chemical Transformation of a Molecular Film by Subexcitation Electrons
Richard Balog and Eugen Illenberger
Phys. Rev. Letters 91 (2003) 213201.
[3] Site-Specific Dissociation of DNA Bases by Slow Electrons at Early Stages of Irradiation
Hassan Abdoul-Carime, Sascha Gohlke and Eugen Illenberger
Phys. Rev. Letters 92 (2004) 168103.