UV absorption spectrum of the C2 Criegee intermediate CH3CHOO
Mica C Smith1, Wei-Lun Ting2, Chun-Hung Chang2
1Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, USA.
The Journal of Chemical Physics
|August 24, 2014
Summary
Researchers measured the UV spectrum of the CH3CHOO Criegee intermediate. Its absorption band is similar in intensity to CH2OO but blue-shifted, leading to a slower atmospheric photolysis rate.
Area of Science:
- Atmospheric Chemistry
- Spectroscopy
- Chemical Kinetics
Background:
- Criegee intermediates are key species in atmospheric oxidation processes.
- Understanding their reactivity and spectral properties is crucial for atmospheric modeling.
- Previous studies have focused on the simplest Criegee intermediate, CH2OO.
Purpose of the Study:
- To measure the UV absorption spectrum of the CH3CHOO Criegee intermediate.
- To determine the absolute absorption cross sections of CH3CHOO.
- To compare the spectral properties and photolysis rates of CH3CHOO with CH2OO.
Main Methods:
- Transient absorption spectroscopy in a flow cell.
- Laser depletion in a molecular beam.
- Measurement of absolute absorption cross sections at specific wavelengths.
Main Results:
- The UV spectrum of CH3CHOO was successfully measured.
- Absolute absorption cross sections were determined at 308 nm and 352 nm.
- The peak UV cross section was found to be 1.27 × 10(-17) cm²/molecule at 328 nm, blue-shifted by 14 nm compared to CH2OO.
Conclusions:
- CH3CHOO exhibits a UV absorption band similar in intensity but blue-shifted relative to CH2OO.
- This spectral shift results in an estimated 20% slower photolysis rate for CH3CHOO in the atmosphere.
- The findings provide essential data for atmospheric chemistry models.
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