Smith Carina A, Pope Francis D, Cronin Bríd, Parkes Clare B, Orr-Ewing Andrew J
School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
J Phys Chem A. 2006 Oct 19;110(41):11645-53. doi: 10.1021/jp063713y.
Absorption cross sections for the A1A2-X1A1 electronic transition of formaldehyde have been measured by ultraviolet (UV) laser absorption spectroscopy in the tropospherically significant wavelength range 300-340 nm, over which HCHO is photochemically active. Absorption cross sections are reported at two temperatures, 294 and 245 K and at a spectral resolution of 0.0035 nm (0.35 cm-1). At this resolution, greater peak absorption cross sections are obtained for many of the sharp spectral features than were previously reported. To simulate atmospheric conditions in the troposphere, the effects of adding a pressure of nitrogen of up to 500 Torr and of reduced sample temperature were investigated. The overall magnitudes of peak absorption cross sections are largely unaffected by the added pressure of nitrogen, but a modest degree of pressure broadening (0.2-0.3 cm-1 atm-1) is evident in the line shapes. Computer simulations of spectra have been optimized by comparison with wavelength-dependent formaldehyde absorption cross sections for each major vibronic band in the chosen wavelength range. Experimental and computer simulated spectra at 294 and 245 K are compared to test the reliability of the computer simulations for quantification of the effects of temperature on absorption cross sections. All experimental absorption cross section data and tables of input parameters for spectral simulations are available as Supporting Information.
已通过紫外（UV）激光吸收光谱法在对流层重要波长范围300 - 340 nm内测量了甲醛A1A2 - X1A1电子跃迁的吸收截面，在此波长范围内HCHO具有光化学活性。报告了在294 K和245 K两个温度下以及0.0035 nm（0.35 cm-1）的光谱分辨率下的吸收截面。在此分辨率下，许多尖锐光谱特征的峰值吸收截面比之前报道的更大。为了模拟对流层中的大气条件，研究了添加高达500 Torr的氮气压力和降低样品温度的影响。峰值吸收截面的总体大小在很大程度上不受添加的氮气压力影响，但在谱线形状中明显存在适度的压力展宽（0.2 - 0.3 cm-1 atm-1）。通过与所选波长范围内每个主要振动电子带的波长相关甲醛吸收截面进行比较，优化了光谱的计算机模拟。比较了294 K和245 K下的实验光谱和计算机模拟光谱，以测试计算机模拟在量化温度对吸收截面影响方面的可靠性。所有实验吸收截面数据和光谱模拟的输入参数表可作为支持信息获取。
