Weiss Fabian, Kubel Frank, Gálvez Óscar, Hoelzel Markus, Parker Stewart F, Baloh Philipp, Iannarelli Riccardo, Rossi Michel J, Grothe Hinrich
Institut für Materialchemie, Technische Universität Wien, Getreidemarkt 9/BC/01, 1060, Wien, Austria.
Institut für Chemische Technologie und Analytik, TU Wien, Austria.
Angew Chem Int Ed Engl. 2016 Mar 1;55(10):3276-80. doi: 10.1002/anie.201510841. Epub 2016 Feb 16.
The composition of high-altitude ice clouds is still a matter of intense discussion. The constituents in question are ice and nitric acid hydrates, but the exact phase composition of clouds and its formation mechanisms are still unknown. In this work, conclusive evidence for a long-predicted phase, alpha-nitric acid trihydrate (alpha-NAT), is presented. This phase was characterized by a combination of X-ray and neutron diffraction experiments, allowing a convincing structure solution. Furthermore, vibrational spectra (infrared and inelastic neutron scattering) were recorded and compared with theoretical calculations. A strong interaction between water ice and alpha-NAT was found, which explains the experimental spectra and the phase-transition kinetics. On the basis of these results, we propose a new three-step mechanism for NAT formation in high-altitude ice clouds.
高海拔冰云的组成仍是一个激烈讨论的话题。所涉及的成分是冰和硝酸水合物，但云的精确相组成及其形成机制仍然未知。在这项工作中，给出了长期预测的相——α-三水合硝酸（α-NAT）的确凿证据。通过X射线和中子衍射实验相结合对该相进行了表征，从而得到了令人信服的结构解析。此外，记录了振动光谱（红外和非弹性中子散射）并与理论计算进行了比较。发现水冰与α-NAT之间存在强相互作用，这解释了实验光谱和相变动力学。基于这些结果，我们提出了一种高海拔冰云中NAT形成的新三步机制。
