High accuracy transition intensities for ozone

臭氧在地球大气层中的浓度很低。在对流层中，臭氧是一种污染物，主要是人类活动造成的。然而，臭氧即使在痕量浓度下也对人类、动物和植物有害。相反，平流层臭氧，即“臭氧层”，为太阳紫外线辐射提供了极其重要的屏障。人类活动导致平流层臭氧的大量减少，这种减少导致两极空洞的增加。对大气臭氧浓度的研究在很大程度上依赖于使用地面、空中和卫星仪器混合进行的光谱遥感。这些仪器观测臭氧在红外线或紫外线中的特征吸收特性。基于这些观测结果的检索需要准确的实验室数据才能使其有用。特别是目前正在进行的许多大气研究需要紫外线（UV）和红外线（IR）的强度/截面数据，其精确度为1%或更好。不幸的是，正如科学文献中广泛记载的那样，实验室强度测定的情况远不能令人满意。首先，许多测量结果表明，在红外和紫外波长下进行的大气研究之间存在4%至5%的系统差异。其次，虽然实验室测量的紫外截面显示出一定程度的一致性，但红外截面的测量结果却不一致。最近（2012年）的一项分析得出结论，对于关键的10微米区域，测量之间的一致性最多只有4%，强度差异远高于此。在红外区域内还有其他差异。迫切需要为Aura卫星使命（美国航天局）上的TES+OMI、Metop卫星（欧空局）上的IASI+GOME-2、Auqa卫星（美国航天局）上的AIRS等飞行任务解决这一问题。该提案将使用高精度，第一原理量子力学方法来计算光谱的IR和UV部分的跃迁强度。对于IR区域，将采用已经成功用于水和CO2的高精度偶极矩表面计算方法。这些将与测量的跃迁频率相结合，以完成强度精确到约0.5%的谱线列表。将开发新的方法来将计算IR振动-旋转强度（需要电子对角偶极矩）所获得的经验转移到UV中的电子跃迁。初步工作将集中于哈金斯带，还需要进一步发展用于处理核运动的方法，这些计算将提供从臭氧浓度等实验问题中去除的绝对谱线强度/截面的完全独立的评估。结果将通过网络和数据库广泛提供，并提交供纳入用于大气研究的标准汇编，如HITRAN。HITRAN将成为该提案的项目合作伙伴，并对结果进行独立评估。

Ozone is present in low concentrations throughout the Earth's atmosphere. In the troposphere ozone is a pollutant which largely results from human activity. However, ozone is harmful to humans, animals and plants at even trace concentrations. Conversely stratospheric ozone, the ``ozone layer'', provides an extremely important shield of solar ultraviolet radiation. Human activity has resulted in a significant reduction in stratospheric ozone and this loss has lead to increased holes at the poles. Studies of atmospheric ozone concentrations rely heavily on the use of spectroscopic remote sensing from a mixture of ground-based, airborne and satellite instruments. These instruments observe the characteristic absorption features of ozone either in the infrared or the ultraviolet. Retrievals based on these observations require accurate laboratory data to make them useful. In particular the many studies of atmospheric currently being conducted require intensity / cross section data for both ultraviolet (UV) and infrared (IR) which is accurate to 1% or better.Unfortunately, as has been extensively documented in the scientific literature, the situation with the laboratory intensity determinations is far from satisfactory. Firstly, there are many measurements showing systematic differences between atmospheric studies performed at infrared and ultraviolet wavelengths at the 4 to 5 % level. Secondly, while laboratory measurements of the ultraviolet cross sections show a measure of agreement, those for the infrared do not. A recent (2012) analysis concluded that for the key 10 micron region agreement between measurements was only at best 4% with intensity discrepancies much higher than this. There are other discrepancies within the infrared region. There is an urgent need for a solution to this problem for missions such as TES+OMI on Aura satellite mission (NASA), IASI+GOME-2 on Metop satellite (ESA) AIRS on the Auqa satellite (NASA). The proposal will use high accuracy, first principles quantum mechanical methods to compute the transition intensities for both the IR and UV portions of the spectrum. For the IR region, methods of computing high accuracy dipole moment surfaces already used successful for water and CO2, will be employed. These will be combined with measured transition frequencies to complete line lists with intensities accurate to about 0.5%.New methodologies will be developed to transfer the experience gained computing IR vibration-rotation intensities (which require electronically diagonal dipole moments) to electronic transitions in the UV. Initial work will focus on the Huggins band and will also require further development of the methods used for treating nuclear motion.These calculations will provide complete independent assessment of the absolute line intensities / cross sections removed from experimental issues such as the ozone concentration. Results will be made widely available via the web, databases and submitted for inclusion in standard compilations used for atmospheric studies such as HITRAN. HITRAN will be a project partner on the proposal and undertake independent evaluation of the results.