Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Kinetic Studies of the Reactions of IO Radicals Determined by Cavity Ring-Down Spectroscopy



D B. Atkinson, Jeffrey W. Hudgens, A J. Orr-Ewing


We demonstrate the application of cavity ring-down spectroscopy (CRDS) to the measurement of concentrations of IO radical and of reaction rate coefficients for the reaction systems, IO+IO and IO+NO, using the source reaction, O(3P)+CF3I. By monitoring IO radicals, we obtain the 295K rate coefficients, k(O + CF3I) = 6 ± 2 x 10-12 cm3molecule-1 s-1, k(IO + IO) = 1.0 ± 0.4 x 10-10 cm3molecule-1 s-1, and k(IO + NO) = 1.9 ± 0.5 x 10-11 cm3molecule-1 s-1 at the pressures of 1250 Pa (9.4 Torr) and 4000 Pa (30.1 Torr). For the IO A2Π3/2 - X2Π3/2 (2,0) bandhead at 445.04 nm we have determined an absorption cross-section, ς = 7.3 ± 0.7 x 10-17 cm2. Error limits indicate the confidence of two standard deviations and propagate the uncertainty in the absorption cross-section.
Journal of Physical Chemistry A


cavity ring-down spectroscopy, electronic spectrum, IO+IO reaction, IO+NO reaction, Iodine monoxide, O+CF3I reaction, reaction rate coefficient, spectrum


Atkinson, D. , Hudgens, J. and Orr-Ewing, A. (1999), Kinetic Studies of the Reactions of IO Radicals Determined by Cavity Ring-Down Spectroscopy, Journal of Physical Chemistry A, [online], (Accessed April 20, 2024)
Created July 13, 1999, Updated October 12, 2021