Hydrogen bonding frequencies

FACTORS AFFECTING GROUP FREQUENCIES Hydrogen Bonding... 

Figure 15.1 Anharmonic coupling ofthe O-H stretching mode q and a low-frequency hydrogen bond (0...0) mode Q. (a) Potential energy diagram for the low-frequency mode in a single hydrogen bond. The potential energy surfaces as defined by the stretching mode and the quantum levels ofthe low-frequency mode are plotted for the Voh = 0 and 1 states as a function of the slow-mode coordinate Q.

Table 3.3 High-frequency hydrogen-bonded O-H stretching bands of l-ascorbic acid...

We applied SEID spectroscopy to determine the IVR rate of the ground-state vibrational levels of weakly bound complexes. Two kinds of complex are chosen here, one is the hydrogen bonded complex of phenol with water (PI1-H2O) and another the van der Waals complex of m-fluorotoluene with Ar (mFT-Ar). For both complexes, it was found that a great enhancement of the IVR rate occurs by the formation of the complex. The enhancement may be explained as a result of the increase of the density of vibrational levels by the addition of low frequency hydrogen bond or van der Waals modes by the complex formation and also of large vibrational coupling. 

Strong anharmonic coupling between the high-frequency X-H(D) stretching vibration and the low-frequency hydrogen bond X -Y stretching vibration v in each H-bond... 

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