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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-Boltzmann 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.

This case study of Slow Food at the University of Wisconsin-Madison (SFUW) examines the success of a volunteer social innovation that promotes sustainable food access. Using inductive thematic analysis of 19 in-depth, semi-structured interviews of past and current members, advisors, and collaborators, we find that the success of SFUW is consistent with Self-Determination Theory. We find that among the participants, the organization satisfies the basic psychological needs for autonomy, competence, and relatedness, which in turn support intrinsic motivation. In this way, volunteering tasks become interesting, fun, and are more likely to be performed over time. The findings suggest that needs fulfillment and intrinsic motivation are linked to creating a self-propagating social innovation where volunteers generate new ideas and successfully transfer skills to others.

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