【作者】 宋科峰；

【导师】 胡水明；

【作者基本信息】 中国科学技术大学 ， 物理化学， 2010， 博士

【摘要】 分子光谱学自诞生以来,一直是一门重要的学科,而且也随着科技的飞速发展在不断地进步,帮助人们不断了解分子的结构和性质。现在这门学科已被广泛地应用于光化学、天文和环境科学等研究领域。特别关于大气分子的研究对于更好地了解温室效应的产生细节,大气分子的光化学性质和对臭氧层的影响,以及大气污染机制都有重要的影响。本论文的主要工作将致力于部分大气分子的同位素研究,我们的结果将有助于完善现有的光谱数据库,并修正分子的有效哈密顿量模型。在第一章中我们将简单介绍分子振转光谱的基本原理,以及利用有效算符来全局拟合分子振转光谱的方法。第二章里将介绍红外傅里叶变换光谱仪(FTS)的原理和本实验室所使用的FTS谱仪的结构；然后介绍光腔衰荡光谱(CRDS)的基本思想以及本实验室自行搭建的一套CW-CRDS装置的结构。通过对痕量乙炔气的光谱测量对装置性能进行了测试。结果表明,其在光谱分辨率达到10-4cm-1的同时,测量灵敏度也好于10-10／cm,具有定量测量和痕量检测的能力。在目前工作的0.8微米波段对乙炔气体的检测限为0.2ppmv。第三章研究集中于大气分子N20的几种同位素。用傅立叶变换光谱仪测量了15N14N16O(546)同位素分子在3500-9000cm-1的红外光谱,经过数据的处理和分析,获得并归属了超过15000条的N20-546谱线。获得133个谱带,其中超过100个为新观测到的谱带。通过CW-CRDS装置先后测量了14N15N16O(456)、15N14N16O(546)和15N216O(556)在6v3带附近的光谱,获得了这三个同位素分子各213、86和191条谱线,其中对N20-456和556,我们还同时观测到了它们的v2+6v3←v2热带,对这些谱带用最小二乘法获得了它们的振转光谱参数,通过对谱线线形的拟合得到了6v3冷带的谱线强度,大部分强度数据的误差估计为4%,与强度相关的跃迁偶极矩平方以及Herman-Wallis系数也一并给出。这些谱带中除N20-556的v2+6v3态未观测到微扰以外,其它的谱带都发现被微扰。通过将我们观测到的谱线位置与当前有效哈密顿量模型参数预测的数据相比较,可以认为目前的有效哈密顿模型必须进一步修正。第四章我们测量了自然丰度的C02气体在7123-7917cm-1波段的CW-CRDS光谱,在灵敏度(噪声等效吸收水平αmin约2×10-10cm-1)下,可以归属共2478条谱线为12C16O2、16O12C17O和16O12C18O分子的吸收线,谱线的强度从1.22×10-29到4.11×10-25cm/molecule不等,大部分谱线的强度数据精度为3%左右。在我们工作的范围内,我们观测到的谱线大大超过了Mandin获得的金星光谱(384条谱线)；这些数据中的大部分也是第一次被观测到。我们也同时拟合了16012C18O的ΔP=10的有效偶极矩参数,通过对大量新数据的拟合,修正了12C16O2和16O12C18Ooe△p＝11的有效偶极矩参数,这些新的参数将有助于CO2光谱数据库(CDSD)数据的更新。通过对比我们的结果与最新版本的CDSD数据,种种超过实验误差范围以外的差异表明,我们观测到的数据对进一步修正不同的EH模型参数是非常有价值的。我们还测量了自然丰度的CO2在12543-12784cm-1范围内的光谱,获得了12C16O2的4个泛频谱带,其中包括2个热带。光谱参数及跃迁偶极矩均已给出。本实验的数据与CDSD、Campargue等人的数据(仅有谱线位置)比较发现,我们的谱线位置跟Campargue是吻合的,但与CDSD差异较大,这很有可能是由于CDSD未考虑在高波数范围(>9650cm-1)的光谱数据,我们的数据将十分有助于CDSD的修正。更多还原

【Abstract】 The molecular spectroscopy has long been an important field and achieved great progress owing to the rapid development of scientific instruments in recent years. It helps to understand the structures and properties of molecules and plays an important role in photochemistry, astrophysical and environmental applications. In particular, the studies on the atmospheric molecules is essential for a better understanding of the details of the green house effect, the influences to the ozonosphere from atmospheric photochemistry, and also the mechanism of the air pollution. The present thesis is de-voted to the studies of several atmospheric molecules including their isotopologues. The results can be applied to improve the present spectroscopy database of these im-portant molecules, and also to improve the effective Hamiltonian model.In chapter 1 the fundamentals of the ro-vibrational spectroscopy will be intro-duced. The basic ideas of the effective operator method toward the global fitting of the molecular spectra will be also presented.In chapter 2 the principle of Fourier-transform (FT) spectrometer which was ap-plied in our lab will be presented. The idea and configuration of the continues-wave (cw) cavity ring down spectroscopy (CRDS) is given. To test the performance of the cw-CRDS built in our lab, the spectroscopy of trace acetylene gas was measured. The results shows that a sensitivity of 10-10/cm, has been achieved accompanied with a spectral resolution of 10-4cm-1. The quantitative measurement and trace detection capabilities are also demonstrated. At the present working frequency of 0.8μm, the detection limit of C2H2 was determined to 0.2ppmv.In chapter 3 we focused on several isotopologues of the atmospheric molecule N2O. The FT spectra of 15N14N16O-enriched nitrous oxide has been recorded at the Doppler limited resolution in the 3500-9000cm-1 region. More than 15000 tran-sitions of 15N14N16O have been observed and assigned based on the global effective Hamiltonian mode. The band-by-band analysis led to the determination of the ro-vibrational parameters of totally 133 bands, in which more than 100 bands were ob-served for the first time. Then the CRDS spectra of 14N15N16O(456),15N14N16O(546) and 15N216O(556) near the 6v3 band have been recorded. In total 213,86 and 191 transi- tions were observed for the three isotopologues respectively. For N2O-456 and 556, the v2+6v3←v2 hot band was also observed. The ro-vibrational spectroscopic parame-ters of the upper states are determined from least squares fitting of the transitions. The absolute line intensities of the 6v3 cold bands have been also retrieved by a multi-line fitting procedure from the spectra with an estimated accuracy of 4%for majority of the unblened lines. The vibrational transition dipole moment values and the empirical Herman-Wallis coefficients are also presented. Except the v2+6v3 band of N2O-556, other four bands studied in this work are found to be perturbed. The comparison of the observed line positions to those predicted using effective Hamiltonian models indicates that the effective Hamiltonian model can be further improved with taking into account of the present results.In chapter 4, it will be presented the study of the spectra of CO2 (with natu-ral abundance)in the 7123-7917cm-1 region using a cw-CRDS spectrometer. The achieved sensitivity (noise equivalent absorption) in the order ofαmin～2×10-10cm-1) has allowed to assign 2478 transitions to the 12C16O2,16O12C17O and 16O12C18O iso-topologues, with intensities ranging from 1.22×10-29 to 4.11×10-25cm/molecule. An average uncertainty for the intensities was estimated to be 3%. It represents an impor-tant improvement as in the considered region, the most extensive set of experimental data was the early measurements from Venus spectra by Mandin which only includes 384 transitions. The majority of these lines were measured for the first time. The ef-fective dipole moment parameters of the△P=10 series of transitions in 16O12C18O were also retrieved from the fitting. The previous set of effective dipole moment pa-rameters of the△P=11 series of transitions in the principle isotopologue was refined leading to important differences for the parameters describing the vibrational and rota-tional dependencies. The obtained results will be used to improve the CDSD databank. We also compared our results to the current version of CDSD, the deviation which be-yond the experimental uncertainties illustrated that the obtained results will be valuable to improve different EH models used to generate the CDSD. The CRDS spectrum of 12C16O2 in the region of 12543-12784cm-1 has also been studied.4 overtone bands were observed, including 2 hot bands. The spectral parameters and transition dipole moments were also retrieved. The comparison with CDSD and Campargue’s line posi-tion data shows that our data was in good agreement with Campargue’s data, but with larger deviation from the data of CDSD. This can be a result from that the present model used in the CDSD database has not include the spectral data over> 9650cm-1. It indicates that the present data will be of particular importance to improve the quality of the CDSD database.更多还原