On Fri, 10 Nov 2017 14:04:26 -0800, Dale Tronrud <de...@daletronrud.com> wrote: ... > > My belief is that the fact that our spot intensities represent the >amplitude (squared) of a series of Sin waves is the result of the hard >work of people like Bob who give us monochromatic illumination. >"Monochromatic" simply means it is a pure Sin wave. If Bob could get >that shiny new ring of his to produce an electromagnetic square wave his >users would still get diffraction patterns with spots but they would >have to come up with programs that would perform Fourier summations of >square waves to calculate electron density. Our instrument is an analog >computer for calculating the Sin wave Fourier transform of the electron >density of our crystal because we designed it to do exactly that. > >Dale Tronrud > ...
Hi Dale, Well, perhaps I understand you wrongly, but I'd say if Bob would succeed in making his synchrotron produce "square" instead of sine waves then we would not have to change our programs too much, because a "square wave" can be viewed as (or decomposed into) superpositions of a sine wave of a given frequency/energy with its higher harmonics, at known amplitude ratios. This would be similar in some way to a Laue experiment, but not using a continuum of energies, only discrete ones. The higher harmonics would just change the intensities a bit (e.g. the 1,2,3 reflection would get some additional intensity from the 2,4,6 and 3,6,9 reflection), and that change could to a large extent be accounted for computationally, like we currently do in de-twinning with low alpha. That would probably be done in data processing, and might not affect the downstream steps like map calculation. best, Kay
