[Studies on halogen quenching through the Stern-Volmer plot (author's transl)]

Area of Science:

• Radiochemistry
• Physical Chemistry
• Organic Chemistry

Background:

• Halogenated organic compounds are widely used, and understanding their interaction with radiation is crucial.
• Quenching effects influence the efficiency of various processes, including scintillation counting and radiation detection.
• Previous studies have explored quenching but lacked detailed mechanistic insights for specific halogenated compounds.

Purpose of the Study:

• To investigate and quantify the halogen quenching effect in halogenated benzenes, methanes, and ethanes.
• To determine the relationship between quenching constants and molecular structure/properties.
• To elucidate the mechanism of halogen quenching, particularly concerning exciplex formation.

Main Methods:

• Accurate measurement of halogen quenching using internal conversion electrons emitted from 113Sn-113mIn.
• Determination of quenching constants via Stern-Volmer plots for various halogen quenchers.
• Correlation analysis between quenching constants, halogen substituents, and polarographic half-wave reduction potentials.

Main Results:

• Quenching constants increase with the number of halogen substituents, showing linear trends in benzenes and exponential trends in methanes/ethanes.
• Isomers of halogenated compounds exhibit distinct quenching constants.
• A linear relationship was observed between the logarithm of the quenching constant and the polarographic half-wave reduction potential.
• Electron excitation yielded higher quenching constants than UV excitation for halogenated methanes.

Conclusions:

• The study provides quantitative data on halogen quenching in diverse organic molecules.
• Results suggest that molecular structure, electronic properties, and excitation methods significantly influence quenching efficiency.
• Exciplex formation is proposed as a key mechanism underlying the observed halogen quenching phenomena.