andyfitch
When spinning a non-cylindrical sample, such as a pellet about a diameter or a pharmaceutical tablet, or simply having a capillary that is not well aligned so that it oscillates partially in and out of the beam, the peaks will have a sinusoidal oscillation superimposed onto their general form. Does anyone know a way of dealing with such data? I had a stab at it
with user_defined_conv with a Sin function, but without success.
alancoelho
Hi Andy
Spinning a sample in the axial plane produces a hat aberration with the hat size changing as a function of Cos(Th); the Sample_Tilt macro can be used to correct for this.
I haven't given much though to the case of a wobble in a spinning capillary. I think this may be more complicated. If we were to consider just a slice of the capillary (a disc) then the disc would be rotating off center. This off-center spinning would be akin to a larger disc but with a lower density at the outsides of the disc. Other discs along the sample could be processing differently and the result could be complex.
For a particular disc; the larger than expected discs would result in broader peak shapes that again changes as a function of Cos(Th). My feeling is that Sample_Tilt may well be a good approximation to describing the whole capillary wobble. To test this, one can simulate disc aberrations for a particular wobble, then sum the aberrations to produce the final aberration and to then see of it is easily approximated with a Cos(Th) hat or maybe a Cos(Th) Gaussian. Its something I could look into but isn't it just easier to align the instrument :)
cheers
alan
andyfitch
After an exchange with Alan offline, he suggested using scale_phase_X, so including scale_phase_X = aa + bb Sin(cc X Deg + dd) ; allowed an oscillating profile to be superimposed on top of the normal peak profile, simulating the effect of a regularly wobbling sample.