Stark Harald, Brown Steven S, Burkholder James B, Aldener Mattias, Riffault Veronique, Gierczak Tomasz, Ravishankara A R
NOAA, Earth System Research Laboratory, 325 Broadway, Boulder, Colorado 80305, USA.
J Phys Chem A. 2008 Oct 2;112(39):9296-303. doi: 10.1021/jp802259z. Epub 2008 Aug 27.
Band strengths for the second (3nuOH) and third (4nuOH) overtones of the OH stretch vibration of peroxynitric acid, HO2NO2 (PNA) in the gas-phase were measured using Cavity Ring-Down Spectroscopy (CRDS). Both OH overtone transitions show diffuse smoothly varying symmetrical absorption profiles without observable rotational structure. Integrated band strengths (base e) at 296 K were determined to be S(3nuOH) = (5.7 +/- 1.1) x 10(-20) and S(4nuOH) = (4.9 +/- 0.9) x 10(-21) cm(2) molecule(-1) cm(-1) with peak cross sections of (8.8 +/- 1.7) x 10(-22) and (7.0 +/- 1.3) x 10(-23) cm(2) molecule(-1) at 10086.0 +/- 0.2 cm(-1) and 13095.8 +/- 0.4 cm(-1), respectively, using PNA concentrations measured on line by Fourier-transform infrared and ultraviolet absorption spectroscopy. The quoted uncertainties are 2sigma (95% confidence level) and include estimated systematic errors in the measurements. OH overtone spectra measured at lower temperature, 231 K, showed a narrowing of the 3nuOH band along with an increase in its peak absorption cross section, but no change in S(3nuOH) to within the precision of the measurement (+/-9%). Measurement of a PNA action spectrum showed that HO2 is produced from second overtone photodissociation. The action spectrum agreed with the CRDS absorption spectra. The PNA cross sections determined in this work for 3nuOH and 4nuOH will increase calculated atmospheric photolysis rates of PNA slightly.
利用光腔衰荡光谱法（CRDS）测量了气相中过氧硝酸（HO₂NO₂，简称PNA）OH伸缩振动的第二泛频（3νOH）和第三泛频（4νOH）的谱带强度。两个OH泛频跃迁均呈现出漫射状、平滑变化的对称吸收谱，未观察到转动结构。在296 K下测定的积分谱带强度（以e为底）为S(3νOH) = (5.7 ± 1.1) × 10⁻²⁰ 和S(4νOH) = (4.9 ± 0.9) × 10⁻²¹ cm² molecule⁻¹ cm⁻¹，在10086.0 ± 0.2 cm⁻¹ 和13095.8 ± 0.4 cm⁻¹处的峰值截面分别为(8.8 ± 1.7) × 10⁻²² 和(7.0 ± 1.3) × 10⁻²³ cm² molecule⁻¹，这是通过傅里叶变换红外光谱和紫外吸收光谱在线测量PNA浓度得到的。所引用的不确定度为2σ（95%置信水平），包括测量中估计的系统误差。在231 K较低温度下测量的OH泛频谱显示，3νOH谱带变窄，同时其峰值吸收截面增大，但在测量精度（±9%）范围内S(3νOH)没有变化。PNA作用光谱的测量表明，第二泛频光解离产生了HO₂。该作用光谱与CRDS吸收光谱一致。这项工作中确定的3νOH和4νOH的PNA截面将使计算出的PNA大气光解速率略有增加。
