利用紅外光譜法研究CH2I和O2反應產生之ICH2OO、CH2OO及CH2OO之量子產率

Abstract

The simplest Criegee intermediate CH2OO, an important species in the atmospheric reaction, has been recently produced from the reaction CH2I + O2. In this reaction, the yield of CH2OO, yCI, decreases with increasing pressure because of the stabilization of the adduct ICH2OO. The pressure-dependence of the yield of CH2OO has been investigated on monitoring different species CH2OO, I, CH2O and other side-products in the reaction. However, there are significant discrepancies among these reported yCI. Part of these discrepancies might be because ICH2OO was not directly observed with these methods. With IR spectrometry, ICH2OO has been characterized by our group. Absorption bands at 1234, 1221, 1087, and 923 cm^-1 provide a definitive identification of gauche-ICH2OO, and absorption band at 1241 cm^-1 provide an identification of anti-ICH2OO. We employed a step-scan Fourier-transform infrared (FTIR) spectrometer to simultaneously observe CH2OO and ICH2OO in the reaction of CH2I + O2 in the pressure range 103–692 Torr. On the integrated absorbance of CH2OO and ICH2OO under various pressure, we derive the relative concentration of CH2OO and ICH2OO and the yield of CH2OO. The yield of CH2OO near 1 atm is greater than previously reported values, which might have significant consequence in atmospheric chemistry.

The simplest Criegee intermediate CH2OO, an important species in the atmospheric reaction, has been recently produced from the reaction CH2I + O2. In this reaction, the yield of CH2OO, yCI, decreases with increasing pressure because of the stabilization of the adduct ICH2OO. The pressure-dependence of the yield of CH2OO has been investigated on monitoring different species CH2OO, I, CH2O and other side-products in the reaction. However, there are significant discrepancies among these reported yCI. Part of these discrepancies might be because ICH2OO was not directly observed with these methods. With IR spectrometry, ICH2OO has been characterized by our group. Absorption bands at 1234, 1221, 1087, and 923 cm^-1 provide a definitive identification of gauche-ICH2OO, and absorption band at 1241 cm^-1 provide an identification of anti-ICH2OO. We employed a step-scan Fourier-transform infrared (FTIR) spectrometer to simultaneously observe CH2OO and ICH2OO in the reaction of CH2I + O2 in the pressure range 103–692 Torr. On the integrated absorbance of CH2OO and ICH2OO under various pressure, we derive the relative concentration of CH2OO and ICH2OO and the yield of CH2OO. The yield of CH2OO near 1 atm is greater than previously reported values, which might have significant consequence in atmospheric chemistry.