Hydrated electron extinction coefficient revisited.

Area of Science:

• Physical Chemistry
• Radiation Chemistry

Background:

• The hydrated electron (e(-))aq is a key reactive species in radiation chemistry.
• Accurate determination of its physical properties, like extinction coefficient, is crucial for quantitative studies.

Discussion:

• This study re-evaluates the extinction coefficient of the hydrated electron (e(-))aq using pulse radiolysis.
• The evaluation is performed relative to the methyl viologen radical cation (*)MV(+), a well-characterized species.
• Previous literature values for the hydrated electron's extinction coefficient at room temperature are found to be underestimated by 10-20%.

Key Insights:

• A revised extinction coefficient for the hydrated electron (e(-))aq at 720 nm and 20°C is determined to be 22,700 M⁻¹ cm⁻¹.
• This value is based on an assumed extinction coefficient of 13,700 M⁻¹ cm⁻¹ for (*)MV(+) at 605 nm.
• The findings necessitate adjustments in the interpretation of past experimental data.

Outlook:

• Revised extinction coefficients will improve the accuracy of second-order reaction rate measurements involving the hydrated electron.
• The study's results will refine estimates of the hydrated electron's integrated oscillator strength.
• Further research may focus on validating these findings across different experimental conditions and temperatures.