Lewis William K, Bemish Raymond J, Miller Roger E
Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
J Chem Phys. 2005 Oct 8;123(14):141103. doi: 10.1063/1.2046672.
A technique that combines infrared laser spectroscopy and helium nanodroplet mass spectrometry, which we refer to as optically selected mass spectrometry, is used to study the efficiency of ion cooling in helium. Electron-impact ionization is used to form He(+) ions within the droplets, which go on to transfer their charge to the HCN dopant molecules. Depending upon the droplet size, the newly formed ion either fragments or is cooled by the helium before fragmentation can occur. Comparisons with gas-phase fragmentation data suggest that the cooling provided by the helium is highly nonthermal. An "explosive" model is proposed for the cooling process, given that the initially hot ion is embedded in such a cold solvent.
一种将红外激光光谱学与氦纳米液滴质谱法相结合的技术（我们称之为光学选择质谱法）被用于研究氦气中离子冷却的效率。电子碰撞电离用于在液滴内形成He(+)离子，这些离子随后将其电荷转移到HCN掺杂分子上。根据液滴大小，新形成的离子要么发生碎片化，要么在碎片化发生之前被氦气冷却。与气相碎片化数据的比较表明，氦气提供的冷却高度非热。鉴于最初的热离子嵌入在如此冷的溶剂中，为冷却过程提出了一个“爆炸式”模型。
