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Justus-Liebig Universit y , Giessen

Explore the electron-impact fragmentation and ionization of Uracil, a key molecule in RNA and DNA, to understand radiation damage on a microscopic level. Detailed experimental setup and conclusions outlined.

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Justus-Liebig Universit y , Giessen

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  1. Justus-Liebig University, Giessen Electron-Impact Fragmentation and Ionisation of Uracil Karl Kramer, Frank Scheuermann, Alexander Theiss,Roland Trassl, Paul Scheier*and Erhard Salzborn *:Institut für Ionenphysik, Innsbruck, Austria

  2. Uracil-Ion-Electron Collisions • Motivation: • Good model for the radiation damage of living organisms on a microscopic level. • Consequential damages caused by secondary electrons.

  3. Uracil Molecule RNA Uracil C4H4N2O2 112amu DNA Thymine C5H6N2O2 126amu

  4. ESI-Setup

  5. Electron Gun

  6. Experimental method

  7. Primary-Ion Spectrum oven for small quantities Ion current / arb. units 112 typ. 22pA uracil+ with collimators at 2x2mm2

  8. Low-Temperature Oven carrier with uracil 62cm

  9. Primary-Ion Spectrum low-temperature oven 112 129 132 Ion current / arb. units typ. 350pA uracil+ with collimators at 2x2mm2 22pA with collimators at 1x1mm2

  10. Product Spectrum e-+112Uc+->mUc+ Fragment+X 5*10-9 mbar 650 eV not normalised count rate

  11. Product-Spectrum Detail 5*10-9 mbar 650 eV not normalised Countrate / arb. units Uc+-O

  12. Fragmentation->CNO++X

  13. Ionisation

  14. Exictation in the ionsource

  15. Excitation, Detail Uc+-CO

  16. Residual-Gas, Detail Uc+-CO 0,25 Watt

  17. ResidualGas, Detail II UC+-CNOH 0,25 Watt

  18. Conclusion • With the low-temperature oven sufficiently high ion currents for investigations of uracil became possible. • With the lowest microwave power the highest ammount of excited uracil ions was found. • Only relative measurements are possible • Fragmentation is substantially more likely than Ionisation. • Outlook: double ionisation of negative uracil ions in order to avoid metastable excited states

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