Ballistic Evaporation and Solvation of Helium Atoms at the Surfaces of Protic and Hydrocarbon Liquids
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- 作者：Alexis M. Johnson ; Diane K. Lancaster ; Jennifer A. Faust ; Christine Hahn ; Anna Reznickova ; Gilbert M. Nathanson
- 刊名：The Journal of Physical Chemistry Letters
- 出版年：2014
- 出版时间：November 6, 2014
- 年：2014
- 卷：5
- 期：21
- 页码：3914-3918
- 全文大小：355K
- ISSN：1948-7185
文摘
Atomic and molecular solutes evaporate and dissolve by traversing an atomically thin boundary separating liquid and gas. Most solutes spend only short times in this interfacial region, making them difficult to observe. Experiments that monitor the velocities of evaporating species, however, can capture their final interactions with surface solvent molecules. We find that polarizable gases such as N2 and Ar evaporate from protic and hydrocarbon liquids with Maxwell鈥揃oltzmann speed distributions. Surprisingly, the weakly interacting helium atom emerges from these liquids at high kinetic energies, exceeding the expected energy of evaporation from salty water by 70%. This super-Maxwellian evaporation implies in reverse that He atoms preferentially dissolve when they strike the surface at high energies, as if ballistically penetrating into the solvent. The evaporation energies increase with solvent surface tension, suggesting that He atoms require extra kinetic energy to navigate increasingly tortuous paths between surface molecules.