Study of the spectra and recombination kinetics of alkyl radicals by molecular modulation spectrometry. Part 1.—The spectrometer and a study of methyl recombination between 250 and 450 K and perdeutero methyl recombination at room temperature

Abstract

Using the technique of molecular modulation spectrometry, the rate constant for methyl radical recombination has been measured to be (4.0 ± 0.9)× 10^–11 cm³ molecule^–1 s^–1 between 250 and 450 K. The rate constant for perdeuteromethyl radicals is identical (within 20 %) at room temperature. With 0.6 nm resolution the effective peak absorption cross-section for methyl radicals at 216 nm is (3.2 ± 0.6)× 10^–17 cm², consistent with an absolute cross-section of (4.2 ± 0.8)× 10^–17 cm². With a resolution of 1.0 nm the observed maximum cross-section for CD₃ absorption, 3.0 × 10^–17, is consistent with an absolute cross-section of (1.0 ± 0.2)× 10^–16 cm².