High Resolution IR-Cavity Ringdown Spectroscopy on Reactive Gas-phase Species

在外层空间的不同区域发现了一种令人惊讶的丰富的化学物质。例如，在濒临死亡的恒星附近，原子结合成分子，作为尘埃形成的种子材料(例如碳化硅)。与地球上不同的是，星际分子通常是高活性的非饱和化合物，甚至是离子性质的(如氢或稀有气体的离子络合物)。这些物种很难在陆地实验室中培养出来，是确定宇宙环境中当地物理条件的有价值的探测器。现在，随着EXES/SOFIA和TEXES/N-GEMINI等望远镜上高分辨率红外仪器的可用，对红外光谱数据的需求大幅增加。此外，高灵敏度的詹姆斯·韦伯太空望远镜很可能已经在2018年开始工作。因此，现在有可能克服红外不透明的地球大气，并使用高分辨率天体物理仪器观察中红外天空。预计已经安排的直线调查将导致新的分子检测。具体地说，没有永久偶极矩并且不能在无线电波长上进行研究的物种将是名单上的新物种。许多预期的分子在中红外波长具有特征光谱。这些光谱不能通过纯理论方法计算到天体物理探测所需的精度水平。在没有新的实验室测量的情况下，数据情况显然是不足的。缺乏实验数据有几个原因。其中一个困难是产生足够丰富的与天体物理相关的分子，因为这些物种非常活跃，而且寿命很短。此外，高分辨率中红外光谱往往缺少足够的光源。这项工作的目的是对与天体物理相关的分子进行高分辨率和极其灵敏的测量。运行在4.5微米以上的大功率量子级联激光器(QCL)和2-4.7微米区域的OPO系统将被用作合适的光源。这些激光系统将是新建成的高灵敏度腔衰荡(CRD)光谱仪的组成部分。红外CRD光谱仪将与特殊的等离子体分子源(激光烧蚀/电子)相结合。放电)以产生原位高分子丰度。在微波辐射的照射下，双共振实验将成为可能，特别适合分子等离子体的研究。在实践中，计划测量碳化硅(如Si2C2)和离子络合物(如[Ar-N2]+)。

There is a surprisingly rich chemistry to be found in different regions in outer space. For example, in the vicinity of dying stars atoms combine to molecules and serve as seed material for dust formation (e.g. silicon carbides). Unlike on earth, interstellar molecules are very often non-saturated compounds that are highly reactive or even of ionic nature (like ionic complexes of hydrogen or noble gases). These species, which are difficult to produce in terrestrial laboratories, are valuable probes to determine the local physical conditions in cosmic environments. Now, with the availability of high-resolution IR instruments on telescopes like EXES/SOFIA and TEXES/N-Gemini a strongly increased demand set in for IR spectroscopic data. In addition, the highly sensitive James Webb space telescope will most likely start already in 2018. Thus, it is now possible to overcome the IR-opaque earthly atmosphere and to view into the mid-IR sky with high resolution astrophysical instruments. It is expected that the already scheduled line surveys will lead to new molecule detections. Specifically species that have no permanent dipole moment and cannot be investigated at radio wavelengths will be new on the list. Many of the expected molecules have characteristic spectra at mid-IR wavelengths. These spectra cannot be calculated by purely theoretical means to the necessary level of precision for astrophysical detections. Without new laboratory measurements the data situation is clearly deficient. The lack of experimental data has several reasons. One difficulty is the production of astrophysically relevant molecules in sufficient abundances, because these species are very reactive and only short-lived. Furthermore, very often adequate light sources for high-resolution mid-IR spectroscopy are missing. The aim of this work is to perform high-resolution and extremely sensitive measurements on astrophysically relevant molecules. Powerful quantum cascade lasers (QCLs) operating above 4.5 mu and OPO systems for the region 2-4.7 mu will be utilized as suitable light sources. These laser systems will be an integral part of the newly to-build highly sensitive cavity-ringdown (CRD) spectrometer. The IR-CRD spectrometer will be combined with special plasma molecule sources (laser ablation/electr. discharge) to produce in-situ high molecule abundances. With the irradiation of microwave radiation double resonance experiments will be feasible which are particularly suitable to investigate molecule plasmas. In practice, it is planned to measure silicon carbides (e.g. Si2C2) and ionic complexes (like [Ar-N2]+).