Average antisymmetric methylene

Figure 6. Average antisymmetric methylene band position (Va 2) of the hydrocarbon backbone in SAMs from normal alkanethiols. All measured band positions were reproducible within 0.5 cm of the reported average value.

Since the transition moments of the antisymmetric and symmetric CH2 stretching vibrations and the methylene chain axis are mutually perpendicular, the average orientation angle y of the hydrocarbon chain axis around the surface normal is obtained to be 27° by the orthogonal relation... 

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