Charvat A, Stasicki B, Abel B
Institut für Physikalische Chemie der Universität Göttingen, Tammannstrasse 6, D-37077 Göttingen, Germany.
J Phys Chem A. 2006 Mar 9;110(9):3297-306. doi: 10.1021/jp055165e.
In the present article a novel approach for rapid product screening of fast reactions in IR-laser-heated liquid microbeams in a vacuum is highlighted. From absorbed energies, a shock wave analysis, high-speed laser stroboscopy, and thermodynamic data of high-temperature water the enthalpy, temperature, density, pressure, and the reaction time window for the hot water filament could be characterized. The experimental conditions (30 kbar, 1750 K, density approximately 1 g/cm3) present during the lifetime of the filament (20-30 ns) were extreme and provided a unique environment for high-temperature water chemistry. For the probe of the reaction products liquid beam desorption mass spectrometry was employed. A decisive feature of the technique is that ionic species, as well as neutral products and intermediates may be detected (neutrals as protonated aggregates) via time-of-flight mass spectrometry without any additional ionization laser. After the explosive disintegration of the superheated beam, high-temperature water reactions are efficiently quenched via expansion and evaporative cooling. For first exploratory experiments for chemistry in ultrahigh-temperature, -pressure and -density water, we have chosen resorcinol as a benchmark system, simple enough and well studied in high-temperature water environments much below 1000 K. Contrary to oxidation reactions usually present under less extreme and dense supercritical conditions, we have observed hydration and little H-atom abstraction during the narrow time window of the experiment. Small amounts of radicals but no ionic intermediates other than simple proton adducts were detected. The experimental findings are discussed in terms of the energetic and dense environment and the small time window for reaction, and they provide firm evidence for additional thermal reaction channels in extreme molecular environments.
在本文中，重点介绍了一种用于在真空中对红外激光加热的液体微束中的快速反应进行快速产物筛选的新方法。通过吸收能量、冲击波分析、高速激光频闪观测法以及高温水的热力学数据，可以对热水细丝的焓、温度、密度、压力和反应时间窗口进行表征。细丝寿命期间（20 - 30纳秒）存在的实验条件（30千巴、1750开尔文、密度约为1克/立方厘米）极为极端，为高温水化学提供了独特的环境。对于反应产物的探测，采用了液体束解吸质谱法。该技术的一个决定性特征是，离子物种以及中性产物和中间体可以通过飞行时间质谱法进行检测（中性物质作为质子化聚集体），而无需任何额外的电离激光。在过热束爆炸分解后，高温水反应通过膨胀和蒸发冷却有效地猝灭。对于超高温、超高压和超高密度水化学的首次探索性实验，我们选择了间苯二酚作为基准体系，它足够简单，并且在远低于1000开尔文的高温水环境中已得到充分研究。与通常在不太极端和密集的超临界条件下发生的氧化反应不同，我们在实验的狭窄时间窗口内观察到了水合作用和少量的氢原子夺取。检测到少量自由基，但除了简单的质子加合物外没有检测到其他离子中间体。根据高能和密集环境以及小反应时间窗口对实验结果进行了讨论，它们为极端分子环境中的额外热反应通道提供了确凿证据。
