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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Ultraviolet Photolysis of HCHO:Absolute HCO Quantum Yields by Direct Detection of the HCO Radical Photoproduct
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Ultraviolet Photolysis of HCHO:Absolute HCO Quantum Yields by Direct Detection of the HCO Radical Photoproduct

机译：HCHO的紫外光解：直接检测HCO自由基光产物的绝对HCO量子产率

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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 ~0.0035 nm)measurements of absorption cross-sections of HCHO,sigma_(HCHO)(lambda),AND relative HCO quantum yields.Absolute PHI_(HCO)values were measured at seven wavelengths,lambda=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 PHI_(HCO)measurements display greater variability as a function of wavelength than the current NASA-JPL recommendations for PHI_(HCO).The absolute PHI_(HCO)(LAMBDA)determinations and previously measured(SIGMA_(HCHO)(LAMBDA))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,PHI_(HCO)(sigma)sigma_(HCHO)(lambda),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 /(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 PHI_(HCO)(lambda)sigma_(HCHO)(lambda)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 PHI_(H2+CO)(lambda)sigma_(HCHO)(lambda)for the molecular(H2 + CO)photofragmentation channel,produced using the measured PHI_(HCO)(lambda)sigma_(HCHO)(tau)values,are also provided at 0.1 and 1.0 nm resolution.
机译：测量了对流层相关波长范围（λ）在300至330 nm之间的HCHO光解自由基（H + HCO）通道的绝对量子产率PHI_（HCO）。内置的紫外（UV）吸收和腔衰荡（CRD）组合检测光谱仪。该仪器以前用于高分辨率（光谱分辨率〜0.0035 nm）HCHO吸收截面的测量，sigma_（HCHO） λ和相对HCO量子产率。使用基于同时UV的独立校准技术，在λ= 303.70,305.13,308.87,314.31,320.67,325.59和329.51 nm的七个波长下测量PHI_（HCO）绝对值。 HCHO和Cl2的光解作用。这些PHI_（HCO）测量值比波长函数具有更大的可变性，比目前NASA-JPL推荐的PHI_（HCO）建议值更大.PHI_（HCO）（LAMBDA）的绝对测定和先前测量的值）（LAMBDA））用于该方法的结果是一整套有关绝对自由基量子产率与HCHO吸收截面PHI_（HCO）（σ）sigma_（HCHO）（lambda）乘积的数据），波长范围为302.6至331.0 nm，波长分辨率为0.005 nm。该光化学参数的乘积与高分辨率太阳光子通量数据结合计算出HCHO对自由基（H + HCO）通道的综合光解速率， J（HCO）。与最新的NASA-JPL建议进行比较，报告的波长分辨率为1 nm，建议在0°太阳天顶角（SZA）时/ HCO增加25％，在高SZA（80°S）时增加到33％ ）。与当前HCHO数据相比，计算出的光解速率的差异部分是由于当前数据集的更高波长分辨率引起的，并突出显示了使用高分辨率光谱技术获得HCHO完整且准确的图像的重要性光解离n个过程。所有实验PHI_（HCO）λsigma_（HCHO）（λ）数据均可用于302.6-331.0 nm波长范围（在294和245 K以及200 Torr以下的N2浴气体下）作为波长的支持信息分辨率为0.005、0.1和1.0 nm。使用测得的PHI_（HCO）（）生成的分子（H2 + CO）光碎裂通道的PHI_（H2 + CO）（λ）sigma_（HCHO）（lambda）的等效数据集还提供0.1和1.0 nm分辨率的λsigma_（HCHO）（tau）值。

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