Question

Absolute Gonfiguration of
H
CHO-
анон
is
снаас​

Answer 1

Answer:

Abstract

Absolute quantum yields for the radical (H + HCO) channel of HCHO photolysis, ΦHCO, have been measured for the tropospherically relevant range of wavelengths (λ) 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 ∼0.0035 nm) measurements of absorption cross-sections of HCHO, σHCHO(λ), and relative HCO quantum yields. Absolute ΦHCO values were measured at seven wavelengths, λ = 303.70, 305.13, 308.87, 314.31, 320.67, 325.59, and 329.51 nm, using an independent calibration technique based on the simultaneous UV photolysis of HCHO and Cl2. These ΦHCO measurements display greater variability as a function of wavelength than the current NASA-JPL recommendations for ΦHCO. The absolute ΦHCO(λ) determinations and previously measured σHCHO(λ) were used to scale an extensive set of relative HCO yield measurements. The outcome of this procedure is a full suite of data for the product of the absolute radical quantum yield and HCHO absorption cross-section, ΦHCO(λ)σHCHO(λ), at wavelengths from 302.6 to 331.0 nm with a wavelength resolution of 0.005 nm. This product of photochemical parameters is combined with high-resolution solar photon flux data to calculate the integrated photolysis rate of HCHO to the radical (H + HCO) channel, J(HCO). Comparison with the latest NASA-JPL recommendations, reported at 1 nm wavelength resolution, suggests an increased J(HCO) of 25% at 0° solar zenith angle (SZA) increasing to 33% at high SZA (80°). The differences in the calculated photolysis rate compared with the current HCHO data arise, in part, from the higher wavelength resolution of the current data set and highlight the importance of using high-resolution spectroscopic techniques to achieve a complete and accurate picture of HCHO photodissociation processes. All experimental ΦHCO(λ)σHCHO(λ) data are available for the wavelength range 302.6−331.0 nm (at 294 and 245 K and under 200 Torr of N2 bath gas) as Supporting Information with wavelength resolutions of 0.005, 0.1, and 1.0 nm. Equivalent data sets of ΦH2+CO(λ)σHCHO(λ) for the molecular (H2 + CO) photofragmentation channel, produced using the measured ΦHCO(λ) σHCHO(τ) values, are also provided at 0.1 and 1.0 nm resolution.

Supporting Information

Tabulated numerical data for the wavelength-dependence of the product of the HCO radical quantum yield (ΦHCO) from HCHO photolysis and HCHO absorption cross-section, σHCHO, measured at 294 and 245 K in the presence of 200 Torr of N2 bath gas (the 245 K data were calculated using αHCOrel and σHCHO measurements at 245 K, but scaled with absolute ΦHCO values for T = 294 K); all data for wavelengths from 302.6 to 331.0 nm, with resolutions of 0.005, 0.1, and 1.0 nm; the derived products of the molecular (H2 + CO) quantum yield and HCHO absorption cross-sections, ΦH2σHCHO, at T = 294 and 245 K and with 200 Torr of N2 bath gas at 0.1 and 1.0 nm wavelength resolution between 302.6 and 331.0 nm, which are valid if ΦH2 +  ΦHCO = 1.

Explanation:

Hi...

Hope it helps you....