Line narrowing elucidation

More detailed information on motion within the Cig chains, at least the timescales that are relevant, are obtained by C NMR relaxation studies [5p]. Several C NMR studies of Cig-derivatized silicas and other n-alkyl analogs have been reported [5n,p,37] Even more detail on the motion can be obtained by wide line H NMR spectroscopy (a technique that does not have high resolution) on Cig-silica samples in which deuterium has been selectively substituted for protons [50]. In this approach, the line-narrowing effects of motion on the broad, quadrupole-based H NMR linewidth of a mechanically static sample is modeled theoretically for specific trial motions to elucidate the detailed nature of the motion. As an example. Figure 34.32 shows experimental H spectra, and the corresponding theoretical simulation for a dry sample of (l-d2)-Ci8-silica as a function of temperature. From the theoretical simulations, based on trial... 

Figure 12 shows non-line-narrowed, but already well-resolved emission and excitation spectra of [Ru(bpy)3] doped into [Zn(bpy)3] (0104)2 with a resolution of about 3 cm", which is clearly inhomogeneously determined. These spectra can be used well for a discussion of the properties of the chromo-phores and will allow us to elucidate important features of the electronic structure and of the vibronic coupling properties of the lowest excited states, although this guest/host system presents some intricacies which become distinctly apparent, when the spectral resolution is further increased (for details see Sect. 3.2.1 and Sect. 3.5). 

The initial solution of the crystal structure of the Torpedo enzyme [28], followed by the mammalian AChE structure [29], revealed that the active center serine lies at the base of a rather narrow gorge that is lined heavily with aromatic residues (Fig. 11-6). The enzyme carries a net negative charge, and an electrostatic dipole is oriented on the enzyme to facilitate diffusional entry of cationic ligands. Crystal structures of several inhibitors in a complex with AChE also have been elucidated [25]. 

It is noteworthy that the width of an absorption signal is inversely proportional to the lifetime of the excited state (Heisenberg s uncertainty principle). Hence, for gases, the lifetime is long and the absorption lines are sharp. This is why small di- or triatomic molecules sampled in the gas state and at low pressures can lead to spectra containing narrow regular bands whose positions enable the elucidation of the various energetic states predicted by the theory. 

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