Perfectly resolving instrument

If we are observing a spectrum o(x ) with the aid of an instrument having a characteristic response function s(x — x ), then i represents the data acquired. If we have a perfectly resolving instrument, then s(x — x ) is a Dirac function, and our data i(x) directly represent the true spectrum, that is, o(x). In this case we have no need for deconvolution. 

Measurements of surface disorder require a high resolving power (the ability to distinguish two close-lying points in the diffraction pattern). Quantitative measurements of surface disorder are limited in the following manner, the worse the resolving power, the smaller the maximum scale of surface disorder that can be detected. For example, if the maximum resolvable distance of the diffractometer is 100 A, then a surface that has steps spaced more than 100 A apart will look perfect to the instrument. The theoretical analysis of disorder is much simpler than that for atomic positions. 

Analysis of analytical requirement in such detail may at first sight seem daunting, but the investment in time will be of great value. Embarking on such an exercise should not necessarily end in an automated instrument—it is perfectly possible that the end result is that the analyses are discontinued owing to Hmited value in the results. However, in the main, a compromise but easy-to-use automatic solution will result which will be used reliably on a routine basis. One of the major questions that needs to be resolved is how in general terms the analyses should be carried out. Some of the available strategies are outhned later in this chapter. 

With magnetic sector instruments a resolving power of up to / = 10,(XX) can routinely be employed, even R = 15,(XX). In practice, those instruments are rarely adjusted to resolve beyond R = 10,(XX), e.g., only when interferences of ions of the same nominal m/z need to be excluded. With an instrument in perfect condition, it is possible to achieve higher resolving power typically they are specified to deliver about R 60,(XX) (on intensive peaks). 

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