Absorption cross-sections of the C-H overtone of volatile organic compounds: 2 methyl-1,3-butadiene (isoprene), 1,3-butadiene, and 2,3-dimethyl-1,3-butadiene
Absorption cross-sections of the C-H overtone of volatile organic compounds: 2 methyl-1,3-butadiene (isoprene), 1,3-butadiene, and 2,3-dimethyl-1,3-butadiene
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DOI：
10.1366/000370207779947440
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发表时间：
2007-02-01
影响因子：
3.5
通讯作者：
Dibble, Theodore S.
中科院分区：
文献类型：
--
作者：
Cias, Pawel;Wang, Chuji;Dibble, Theodore S.
许多分子或瞬态自由基在紫外（UV）区有很好的吸收截面，但它们在近红外（NIR）区吸收截面鲜为人知，难以测量。我们提出了一种利用紫外区已知吸收截面来确定未知近红外吸收截面的方法，该方法采用单路紫外吸收光谱和近红外连续波腔衰荡光谱（cw-CRDS）在横臂反应室中同时测量。在不知道实际样品分压（或浓度）的情况下，可以通过两组测量准确地确定近红外吸收截面。该方法通过测量2-甲基-1,3-丁二烯（异戊二烯）的不对称C-H拉伸(3.24 (+/- 0.16)x 10(-22) cm（2)分子（-1））在1651.52 nm处的第一泛音的近红外吸收截面来证明（使用已知值或220转时的吸收截面）。利用大气腔内CH4、CO2和H2O的衰荡光谱对二极管激光波长进行了标定。通过与样品压力测量的比较，该方法也可以用作反应室的压力校准手段，并通过在1651.52 nm处测量1,3-丁二烯和2,3 -二甲-1,3-丁二烯(分别为2.50 (+/- 0.08)x 10（-22）和2.82 (+/- 0.16)x 10(-22) cm（2)分子（-1））的吸收截面证明了这一点。讨论了该方法在同时测量cw-CRDS和单路吸收光谱来确定吸收截面的适用性。索引标题：近红外吸收；近红外吸收截面；异戊二烯;挥发性有机化合物；挥发性有机化合物的仪器;连续波腔衰荡光谱；cw-CRDS。
Many molecules or transient radicals have well-documented absorption cross-sections in the ultraviolet (UV) region, but their absorption cross-sections in the near-infrared (NIR) region are much less often known and are difficult to measure. We propose a method to determine the unknown NIR absorption cross-sections using the known absorption cross-sections in the UV region, in which single-path UV absorption spectroscopy and NIR continuous wave cavity ringdown spectroscopy (cw-CRDS) are employed in a cross-arm reaction chamber for simultaneous measurements. Without knowing the actual sample partial pressures (or concentrations), the NIR absorption cross-sections can be accurately determined through the two sets of measurements. The method is demonstrated by measuring the NIR absorption cross-section of the first overtone of the asymmetric C-H stretch of 2-methyl-1,3-butadiene (isoprene) (3.24 (+/- 0.16) x 10(-22) cm(2) molecule(-1)) at 1651.52 nm using the known value or the absorption cross-section at 220 turn. The diode laser wavelength was calibrated by atmospheric cavity ringdown spectra of CH4, CO2, and H2O. By comparison with sample pressure measurements, this method can also be used as a pressure calibration means for the reaction chamber, and this has been demonstrated with two additional measurements of the absorption cross-sections of 1,3-butadiene and 2,3dimethyl-1,3-butadiene (2.50 (+/- 0.08) x 10(-22) and 2.82 (+/- 0.16) x 10(-22) cm(2) molecule(-1), respectively) at 1651.52 nm. The applicability of the method to determining absorption cross-sections using the simultaneous measurements of cw-CRDS and single-path absorption spectroscopy is discussed. Index Headings: Near-infrared absorption; NIR absorption cross-sections; Isoprene; Volatile organic compounds; VOCs; Continuous wave cavity ringdown spectroscopy; cw-CRDS.