Coherent states hydrogen bonds

A microwave pulse from a tunable oscillator is injected into the cavity by an anteima, and creates a coherent superposition of rotational states. In the absence of collisions, this superposition emits a free-mduction decay signal, which is detected with an anteima-coupled microwave mixer similar to those used in molecular astrophysics. The data are collected in the time domain and Fourier transfomied to yield the spectrum whose bandwidth is detemimed by the quality factor of the cavity. Hence, such instruments are called Fourier transfomi microwave (FTMW) spectrometers (or Flygare-Balle spectrometers, after the inventors). FTMW instruments are extraordinarily sensitive, and can be used to examine a wide range of stable molecules as well as highly transient or reactive species such as hydrogen-bonded or refractory clusters [29, 30]. 

Aromaticity varies with change of state because of the influence of the molecular environment on the interactions that determine aromaticity quantitatively, particularly in nonsymmetrical heterocycles. Comparative calculations of aromaticity indices for molecules in the gas phase and in condensed media with dielectric constants > 1, with or without hydrogen-bonding, showed coherent results for a set of nitrogen heterocycles, including imidazole, pyrrole, pyrazole, 1//-1,2,4-triazole, and benzimidazole. The... 

Acetanilide, and some of its isotopomers, have been studied by INS spectroscopy [56-58]. The dispersion curves of the fully deuterated material have been measured by coherent INS [59]. A comprehensive analysis of acetanilide in the solid state was carried out with molecular dynamics simulations [57]. This includes all the lattice modes, as shown in Fig. 10.27 The simulations suggested that the barrier to the methyl torsion was enhanced when the peptide group is hydrogen-bonded and that this was a through-bond polarization effect. The methyl torsion was... 

In this chapter, coherent low-frequency motions and their role in hydrogen bond dynamics and hydrogen transfer are discussed. In Section 15.2, the basic vibrational excitations and couplings in a hydrogen bond are introduced. Recent results on coherent low-frequency motions of intra- and intermolecular hydrogen bonds in the electronic ground state are presented in Section 15.3. The role of low-frequency motions in excited state intramolecular hydrogen transfer is addressed in Section 15.4, followed by some conclusions (Section 15.5). 

The most common case of solvation is for the incorporation of water molecules, which are almost always involved in hydrogen bonding. Indeed, it is the hydrogen bonding network that contributes to the coherence of the crystal, such that they usually show slower dissolution rates compared to the corresponding anhydrates. Byrn (1982) has illustrated the importance of this topic by stating that there are more than 90 hydrates listed in the USP. 

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