NO(2) quantum yields from ultraviolet photodissociation of methyl and isopropyl nitrate.

Quantum yields, Phi(NO(2)), are reported for the NO(2) formation channel (RO + NO(2)) following photodissociation of methyl and isopropyl nitrate (CH(3)ONO(2) and C(3)H(7)ONO(2)) at the tropospherically relevant wavelengths of 308-320 nm. Measurements were made using ultra-violet (UV) laser absorption and cavity ring down spectroscopy (CRDS) detection of the NO(2) photoproducts. Analysis of CRDS data to obtain NO(2) quantum yields required account to be taken of the spatially inhomogeneous NO(2) distribution resulting from photolysis with a laser beam with a Gaussian intensity profile.

Ultraviolet photolysis of HCHO: absolute HCO quantum yields by direct detection of the HCO radical photoproduct.

Absolute quantum yields for the radical (H + HCO) channel of HCHO photolysis, Phi(HCO), have been measured for the tropospherically relevant range of wavelengths (lambda) between 300 and 330 nm. The HCO photoproduct was directly detected by using a custom-built, combined ultra-violet (UV) absorption and cavity ring down (CRD) detection spectrometer. This instrument was previously employed for high-resolution (spectral resolution approximately 0.