Potential energy crest

The surfaces used in Polanyi and Wong s calculations were for thermoneutral reactions, but since the system has no way of anticipating the shape of the surface past the maximum in the potential energy profile, the results reflect the form of the potential up to and including the crest of the barrier. Together with the results of Mok and Polanyi s investigation this strengthens the conclusion that substantially... 

Another potential source of energy supporting primary production at the ridge crests vents is radiation. Two types of radiation have been detected around hydrothermal systems (1) visible light probably generated by chemical reactions, bubble formation, and... 

Therefore, the molecules moved from the cusp X to the crest Y provide a decrease in the total free energy due to the London interactions. It is true that the molecules below the cusp, A, now have fewer molecules above them than before and this makes their interaction potential less negative, However, the molecules beneath the crest and below the previous planar surface, B, now have a larger number of molecules above them and this makes their interaction potential more negative. It is likely that the last two effects compensate each other. The overall effect of the perturbation on the dispersion interactions is to make the contribution of the latter more negative. The perturbation will grow and... 

The internal dynamics of the methyl group immensely complicates the spectroscopy of these molecules. Of course, this aspect of the problem also provides much of the spectroscopic interest. When the methyl hydrogens of acetaldehyde oscillate around the CC axis, they experience forces arising from the CHO frame of the molecule which vary sinusoidally. As a result, the potential function for internal rotation can be represented by a cosine function in which the crest to trough distance measures the height of the potential barrier. Since the energy barrier to methyl rotation is low in acetaldehyde, the internal motion is one of hindered internal rotation, rather than torsional oscillation. 

---