Extinction Coefficients of NO₂ and N₂O₄

Area of Science:

• Atmospheric Chemistry
• Spectroscopy
• Environmental Science

Background:

• Nitrogen dioxide (NO2) is a key atmospheric pollutant.
• Understanding NO2 spectral properties is crucial for atmospheric modeling.
• Temperature-dependent absorption influences atmospheric measurements.

Purpose of the Study:

• To measure the extinction coefficient of NO2 across a broad spectral range (185-410 nm).
• To investigate the influence of temperature (235-298 K) on NO2 absorption.
• To quantify the impact of nitrogen tetroxide (N2O4) dimer absorption.

Main Methods:

• Spectrophotometric measurement of NO2 extinction coefficients.
• Inclusion of N2O4 measurements to correct for dimer interference.
• Temperature-controlled experimental setup.

Main Results:

• Extinction coefficients for NO2 were determined between 185 and 410 nm.
• A decrease in temperature led to a reduction in NO2 extinction.
• Specifically, a ~10% reduction in extinction was observed between 320-380 nm with decreasing temperature.

Conclusions:

• Temperature significantly affects NO2 spectral absorption.
• Accurate atmospheric measurements require accounting for temperature-dependent NO2 extinction.
• The study provides essential data for atmospheric remote sensing and modeling.