1.65μm附近CH_4分子高分辨率吸收光谱研究

Research on High Resolution Spectrum Measurements of Methane at 1.65 μm

采用连续可调谐二极管半导体激光器为探测光源,以可调怀特型长光程多通池(46.36～1158.90m)作为吸收池,采用直接吸收的方法,探测了室温下1.65μm附近CH4分子的高分辨率吸收光谱。在6043.00～6053.72cm-1范围内探测了5组不同压力和光程下的吸收光谱,观测到了259条线新的CH4分子吸收谱线,实验数据用Gaussian线型进行拟合,得到了这些吸收谱线的线强、线位置以及线强的标准偏差值,并对光谱中难以分辨的吸收谱线进行了分析。探测得到的最小谱线线强是4.3×10-27cm-1·(molcule·cm-2)-1,吸收谱线线强大于3.0×10-24cm-1·(mol·cm-2)-1由于吸收饱和而未被处理,同时所测得的光谱也显示出CH4分子在1.65μm附近有非常丰富的弱吸收谱线和复杂的结构。文中所报道的吸收谱线都是HITRAN2004数据库中所未报道的,而且也未见有其他文献报道过。

The high resolution spectrum of methane was obtained around 1.65 μm using a tunable DFB diode laser with a long adjustable optical path white·cell （46.36-1 158.90 m） at room temperature through the direct absorption technique. The typical line width of the DFB diode laser is about 10 MHz and the wavelength of DFB laser was calibrated by an optical wavemeter. A total of 259 new absorption lines were studied from 6 043.00 to 6 053.72 cm^-1 at five different pressures and optical lengths. All the data were fitted by Gaussian profile, the line intensities, positions and the percent of the statistical standard deviation （σS/S）% of the line intensities were obtained, and the absorption lines which are hard to be distinguished were analyzed in this paper. The weakest absorption line is 4.3×10^-27cm^-1·（mol·cm^-2）^-1, while the lines stronger than 3.0×10^-24 cm^-1·（mol·cm^-2）^-1 were ignored for their saturated absorption due to the long absorption optical length（788-1 000 m）. Meantime, the spectrum shows the abundance of methane weak lines and its extremely complex structure around 1.65 μm. All the lines cannot be found in HITRAN2004 database, and as to our knowledge, they were not reported before by other papers.