Abstract
The vibrational spectrum of the long chain fatty alcohol hexadecanol adsorbed at a water/air interface is studied by sumfrequency (SF) spectroscopy, observing three vibrations of the terminal methyl group. A theoretical analysis is presented that predicts opposite phases of adjacent vibrational modes leading to destructive interference in the SF spectrum. This novel interference effect is reported with enhanced spectral resolution and signal-to-noise ratio. Application of this effect for the determination of the line amplitudes of the degenerate stretching mode yields more precise information on molecular orientation. The tilt angle of the molecular chain with respect to the surface normal in a spontaneously formed monolayer has been determined to be 8.2° ± 1.8°.
Published Version
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