Absorption spectrum and absolute absorption cross sections of CH 3O2 radicals and CH3I molecules in the wavelength range 7473-7497 cm-1

Eszter P. Faragó, Bela Viskolcz, Coralie Schoemaecker, Christa Fittschen

Research output: Article

19 Citations (Scopus)

Abstract

The absorption spectrum of CH3O2 radicals and CH 3I molecules has been measured in the range 7473-7497 cm -1. CH3O2 radicals have been generated by 248 nm laser photolysis of CH3I in the presence of O2, and the relative absorption has been measured by time-resolved continuous-wave cavity ring-down spectroscopy (cw-CRDS). Calibration of the relative absorption spectrum has been carried out on three distinct wavelengths by carefully measuring CH3O2 decays under different experimental conditions and extracting the initial radical concentration (and with this the absolute absorption cross sections) by using the well-known rate constant for the CH3O2 self-reaction. The following, pressure-independent absorption cross sections were determined: 3.41 × 10-20, 3.40 × 10-20, and 2.11 × 10 -20 cm2 at 7748.18, 7489.16, and 7493.33 cm-1. These values are 2-3 times higher than previous determinations (Pushkarsky, M. B.; Zalyubovsky, S. J.; Miller, T. A. J. Chem. Phys. 2000, 112 (24), 10695-10698 and Atkinson, D. B.; Spillman, J. L. J. Phys. Chem. A 2002, 106 (38), 8891-8902). The absorption spectrum of the stable precursor CH3I has also been determined and three characteristic sharp absorption lines with absorption cross sections up to 2 × 10-21 cm2 have been observed in this wavelength range.

Original languageEnglish
Pages (from-to)12802-12811
Number of pages10
JournalJournal of Physical Chemistry A
Volume117
Issue number48
DOIs
Publication statusPublished - dec. 5 2013

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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