Auger electron spectra--the basic data for understanding the Auger effect

Area of Science:

• Nuclear Physics
• Radiochemistry
• Computational Chemistry

Background:

• Auger electron-emitting nuclides exhibit high radiotoxicity when incorporated into DNA.
• Accurate simulation of their emission spectra is essential for understanding this toxicity.
• Previous Monte Carlo codes simulated iodine-125 (125I) Auger cascades, but lacked experimental validation.

Purpose of the Study:

• To validate a Monte Carlo code for simulating Auger cascades using experimental data.
• To refine the understanding of electron spectra from Auger emitters, specifically iodine.
• To investigate the impact of molecular binding on Auger cascade simulations.

Main Methods:

• Adaptation of a Monte Carlo computer code for simulating Auger cascades in xenon.
• Comparison of simulated electron spectra with experimental findings.
• Semi-empirical quantum mechanical calculations for an iodine-labelled thymine molecule.

Main Results:

• The adapted Monte Carlo code showed very good agreement with experimental data for xenon.
• The importance of shake-off electrons and energy considerations in cascade simulations was demonstrated.
• Recalculated electron spectrum for 125I is presented, and Coulomb explosion in condensed phase molecular binding is a possibility.

Conclusions:

• The validated Monte Carlo code provides a reliable tool for simulating Auger cascades and electron spectra.
• Understanding molecular binding effects is critical for accurate radiotoxicity assessment of Auger emitters.
• Further research into condensed-phase effects is warranted.