高分辨高精密甲胺分子C—N伸缩带的兰姆凹陷饱和吸收红外光谱

High-Resolution and High-Accuracy Lamb-Dip Saturated Absorption Infrared Spectra of the C—N Stretching Band of Methylamine

甲胺分子(CH3NH2)是最简单的胺类分子,但由于分子中振动-转动-扭动-反转的相互作用使得其能级结构复杂和丰富密集且谱线强度差异很大的波谱,尤其是在频率中心位于1 044cm-1的C—N伸缩振动带。我们使用利用兰姆凹陷光谱技术自主研发的分辨率为0.4 MHz的二氧化碳激光和微波边带红外光谱仪将甲胺分子的C—N伸缩振动带的多普勒光谱中密集重合在一起的上百条谱线逐条分辨开和精密地测量了它们的跃迁频率。将它们标识归类和对J(J+1)作幂级数展开后,我们求得了27个系列的最初跃迁频率和它们的有效转动常数。

Methylamine(CH3NH2)is the simplest primary amine.Due to the vibration-rotation-torsion-inversion interaction,the energy structures of CH3NH2 are complex and the spectra of CH3NH2 are rich but highly crowded with quite different line intensities,especially in the C—N stretching band of CH3NH2 centered at about 1 044cm-1.We developed a CO2-laser/microwave-sideband spectrometer by using Lamb-dip technique;resolved more than hundreds of overlapped lines in the Doppler limited spectrum with a resolution of 0.4MHz;and precisely measured the transition frequencies of the resolved lines.These lines were clearly assigned and classified into 27 substates.Refined term values of these lines in their excited states were determined and expanded in J(J+1)power-series to determine the substate origins and the effective rotational constants.