Solvated electron extinction coefficient and oscillator strength in high temperature water

Area of Science:

• Physical Chemistry
• Chemical Physics
• Radiation Chemistry

Background:

• The hydrated electron is a key transient species in radiolysis.
• Accurate determination of its properties, like extinction coefficient, is crucial for understanding radiation-induced chemical processes.
• Previous measurements of the hydrated electron's extinction coefficient may have been inaccurate.

Purpose of the Study:

• To accurately determine the decadic extinction coefficient of the hydrated electron at its absorption maximum.
• To investigate the temperature dependence of this coefficient.
• To re-evaluate the integrated oscillator strength of the hydrated electron.

Main Methods:

• Relating transient absorption of hydrated electrons to stable product concentration using scavengers (SF6, N2O, methyl viologen).
• Spectroscopic measurements from room temperature to 380°C.
• Correction for refractive index effects.

Main Results:

• The room temperature decadic extinction coefficient was determined to be 22,500 M⁻¹ cm⁻¹, 10-20% higher than previously accepted values.
• Previous low values were attributed to incorrect radiolysis yield assumptions.
• The revised integrated oscillator strength, corrected for refractive index, is approximately 10% larger than unity.
• Oscillator strength was found to be conserved across the studied temperature range.

Conclusions:

• The revised extinction coefficient and oscillator strength provide a more accurate characterization of the hydrated electron.
• The findings support theoretical models involving the mixing of the hydrated electron's wave function with solvent electronic orbitals.
• This work refines fundamental understanding of electron-water interactions in condensed phases.