10.1021/jp067660w.s001
Francis D. Pope
Francis D.
Pope
Jaron C. Hansen
Jaron C.
Hansen
Kyle D. Bayes
Kyle D.
Bayes
Randall R. Friedl
Randall R.
Friedl
Stanley P. Sander
Stanley P.
Sander
Ultraviolet Absorption Spectrum of Chlorine Peroxide, ClOOCl
American Chemical Society
2007
20 km altitude
product ClOOCl
zenith angle
chlorine peroxide
Ultraviolet Absorption Spectrum
band strengths
Chlorine Peroxide
300 nm
conditions representative
photolysis rates
peak absorbances
path cell
temperature profiles
novel fashion
spectrum result
ozone depletion
ClOOClThe photolysis
O 3
ab initio calculations
Cl 2
CF 2Cl
impurity levels
laser photolysis
JPL
2007-05-24 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Ultraviolet_Absorption_Spectrum_of_Chlorine_Peroxide_ClOOCl/3005548
The photolysis of chlorine peroxide (ClOOCl) is understood to be a key step in the destruction of polar
stratospheric ozone. This study generated and purified ClOOCl in a novel fashion, which resulted in spectra
with low impurity levels and high peak absorbances. The ClOOCl was generated by laser photolysis of Cl<sub>2</sub>
in the presence of ozone, or by photolysis of ozone in the presence of CF<sub>2</sub>Cl<sub>2</sub>. The product ClOOCl was
collected, along with small amounts of impurities, in a trap at about −125 °C. Gas-phase ultraviolet spectra
were recorded using a long path cell and spectrograph/diode array detector as the trap was slowly warmed.
The spectrum of ClOOCl could be fit with two Gaussian-like expressions, corresponding to two different
electronic transitions, having similar energies but different widths. The energies and band strengths of these
two transitions compare favorably with previous ab initio calculations. The cross sections of ClOOCl at
wavelengths longer than 300 nm are significantly lower than all previous measurements or estimates. These
low cross sections in the photolytically active region of the solar spectrum result in a rate of photolysis of
ClOOCl in the stratosphere that is much lower than currently recommended. For conditions representative of
the polar vortex (solar zenith angle of 86<sup>o</sup>, 20 km altitude, and O<sub>3</sub> and temperature profiles measured in
March 2000) calculated photolysis rates are a factor of 6 lower than the current JPL/NASA recommendation.
This large discrepancy calls into question the completeness of present atmospheric models of polar ozone
depletion.