Characteristic length, neutron processes

The complex neutron processes can be described by characteristic lengths. They are a measure of the rectified distance travelled by a neutron in its zigzag path between the start and end of consideration. A detailed descriptimi is given, for example, by Ellis et al. (2003), Ellis and Singer (2007) and Gilchrist (2009) ... 

What then is the structural feature most characteristic of a proton conductor system It is generally believed that a proton is transferred through a solid in one of two distinct ways by a vehicular mechanism, whereby the proton rides on a carrier molecule of type NH4 or HjO ion, or by a Grotthuss mechanism, in which the proton jumps from a donor to a suitably placed acceptor molecule (typically, from H30 to H2O, or from H2O to OH ). How then is such a process sensed in a conventional diffraction experiment The nature of the diffraction method is such that we obtain a time- and space-average of the unit-cell content within the characteristic coherence length of the diffraction process (typically, hundreds of Angstroms), and over the duration of the experiment (days to weeks). This follows from the extremely short photon-electron and neutron-nucleus interaction times ( 10 s), which are significantly shorter than the characteristic time of the fastest of the dynamical processes in the structure ( 10 s for the vibration of a covalently bonded atom). It follows then that some type of structural... 

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