Ultra-low temperature hydrocarbon chemistry in liquid helium droplets

本项目致力于液氦纳米液滴提供的极低温（T = 0.37 K）下天体化学相关反应的研究。液滴是由氦气通过冷却喷嘴的超音速膨胀产生的，并作为“分子束”进入质谱仪检测器。通过让光束通过单个拾取细胞或让它与渗出光束交叉，反应伙伴被沉积在氦纳米液滴上或沉积在氦纳米液滴中。用于监测反应发生的方法有：质谱法、化学发光检测法、耗尽法和激光光谱法。通过测量反应前后氦滴的大小，可以得到反应焓的信息。为了对反应产物进行表征，将使用质谱法和激光光谱法。研究将集中在具有天体化学兴趣的中性-中性反应上。将研究金属原子Si、Al、Fe和Mg与碳氢化合物之间的反应。烃类自由基将由前体烃类气体的热解离产生。这些自由基与金属原子和多环芳烃分子的反应将被研究。此外，还将注意从烃类自由基开始形成大的烃类分子。

The present project is devoted to the study of astrochemically relevant reactions at extremely low temperature (T = 0.37 K) as provided by liquid helium nanodroplets. The droplets are produced by supersonic expansion of helium gas through a cooled nozzle and directed as a “molecular beam” into a mass spectrometer detector. The reaction partners are deposited on or into the helium nanodroplets by letting the beam pass through individual pick-up cells or letting it cross with effusive beams. Several methods are applied to monitor the occurrence of reaction: Mass spectrometry, chemiluminescence detection, depletion technique, and laser spectroscopy. Information about the enthalpy of the reaction is obtained by measuring the size of the helium droplets before and after the reaction. To characterize the reaction products, mass spectrometry and laser spectroscopy will be used. The studies will focus on neu- tral-neutral reactions of astrochemical interest. Reactions between metal atoms Si, Al, Fe, and Mg with hydrocarbons will be studied. Hydrocarbon radicals will be produced by thermal dissociation of the precursor hydrocarbon gas. Reactions of these radicals with metal atoms and PAHs molecules will be studied. Also, attention will be given to the formation of large hydrocarbon molecules starting from the hydrocarbon radicals.