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首页> 外文期刊>Atmospheric Measurement Techniques >An intercomparison of CH3O2 measurements by fluorescence assay by gas expansion and cavity ring-down spectroscopy within HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry)
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An intercomparison of CH3O2 measurements by fluorescence assay by gas expansion and cavity ring-down spectroscopy within HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry)

机译：荧光测定荧光测定荧光测定在黎满气体膨胀和腔循环光谱法（大气化学高度仪表反应器中的荧光测定荧光测定

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Simultaneous measurements of CH3O2 radical concentrations have been performed using two different methods in the Leeds HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry) chamber at 295 K and in 80 mbar of a mixture of 3 : 1 He/O-2 and 100 or 1000 mbar of synthetic air. The first detection method consisted of the indirect detection of CH3O2 using the conversion of CH3O2 into CH3O by excess NO with subsequent detection of CH3O by fluorescence assay by gas expansion (FAGE). The FAGE instrument was calibrated for CH3O2 in two ways. In the first method, a known concentration of CH3O2 was generated using the 185 nm photolysis of water vapour in synthetic air at atmospheric pressure followed by the conversion of the generated OH radicals to CH3O2 by reaction with CH4/O-2. This calibration can be used for experiments performed in HIRAC at 1000 mbar in air. In the second method, calibration was achieved by generating a near steady state of CH3O2 and then switching off the photolysis lamps within HIRAC and monitoring the subsequent decay of CH3O2, which was controlled via its self-reaction, and analysing the decay using second-order kinetics. This calibration could be used for experiments performed at all pressures. In the second detection method, CH3O2 was measured directly using cavity ring-down spectroscopy (CRDS) using the absorption at 7487.98 cm(-1) in the A <- X (nu(12)) band with the optical path along the similar to 1.4 m chamber diameter. Analysis of the second- order kinetic decays of CH3O2 by self-reaction monitored by CRDS has been used for the determination of the CH3O2 absorption cross section at 7487.98 cm(-1), both at 100 mbar of air and at 80 mbar of a 3 : 1 He/O-2 mixture, from which sigma CH3O2 = (1.49 +/- 0.19) x 10(-20) cm(2) molecule(-1) was determined for both pressures. The absorption spectrum of CH3O2 between 7486 and 7491 cm(-1) did not change shape when the total pressure was increased to 1000 mbar, from which we determined that sigma CH3O2 is independent of pressure over the pressure range 100-1000 mbar in air. CH3O2 was generated in HIRAC using either the photolysis of Cl-2 with UV black lamps in the presence of CH4 and O-2 or the photolysis of acetone at 254 nm in the presence of O-2. At 1000 mbar of synthetic air the correlation plot of [CH3O2](FAGE) against [CH3O2](CRDS) gave a gradient of 1.09 +/- 0.06. At 100 mbar of synthetic air the FAGE-CRDS correlation plot had a gradient of 0.95 +/- 0.024, and at 80 mbar of 3 : 1 He/O-2 mixture the correlation plot gradient was 1.03 +/- 0.05. These results provide a validation of the FAGE method to determine concentrations of CH3O2.
机译：已经使用基LEEDSHIRAC（高度仪表化学）室中的两种不同方法在295 k和3：1 HE / O-2和100或1000毫巴的混合物中使用两种不同的方法进行CH3O2自由基浓度的CH3O2自由基浓度的测量。合成空气。第一种检测方法包括使用过量的NO不含CH 3 O 2的CH 3 O 2的间接检测，随后通过气体膨胀（FARE）通过荧光测定检测CH 3 O. FAGE仪器以两种方式校准CH3O2。在第一种方法中，使用在大气压下的合成空气中的185nm光解，然后通过与CH 4 / O-2反应将产生的OH基团转化为CH 3 O 2的185nm光解。该校准可用于在空气中以1000毫巴的Hirac进行的实验。在第二种方法中，通过产生近稳态的CH 3 O 2来实现校准，然后通过其自我反应监测HiRAC内的光解灯并监测随后的CH 3 O 2的衰减，并使用二阶分析衰减动力学。该校准可用于在所有压力下进行的实验。在第二检测方法中，在A < - X（12））带中使用7487.98cm（-1）的吸收，使用腔室（12））带直接测量CH 3 O 2），其中光路类似于类似于1.4 m腔室直径。通过CRD监测的自我反应分析CH3O2的二阶动力学衰减已经用于测定在7487.98cm（-1）的CH3O2吸收横截面，均在100毫巴的空气中和80毫巴的3 ：1 HE / O-2混合物，测定σCH3O2=（1.49 +/- 0.19）×10（-20）cm（2）分子（-1）的压力。当总压力增加到1000毫巴时，CH 3 O 2之间的吸收光谱在7486和7491cm（-1）之间没有改变形状，从中确定Sigma CH3O2与空气中100-1000毫巴的压力范围内的压力无关。在Hirac中使用CL-2的光解，在CH4和O-2存在下使用UV黑色灯的光解或在O-2存在下在254nm处的丙酮的光解。在1000毫巴的合成空气中，[CH3O2]（FAGE）对[CH 3 O 2]（CRD）的相关图给出了1.09 +/- 0.06的梯度。在100毫巴的合成空气中，Fage-CRD相关图具有0.95 +/- 0.024的梯度，并且在80毫巴为3：1 HE / O-2混合物中，相关曲率梯度为1.03 +/- 0.05。这些结果提供了测定CH3O2浓度的FAGE方法的验证。

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