> _diffrn_source_take-off_angle > > The definition seems a little sparse, but might be adequate. I wondered > whether it should say "The angle between the normal to the surface of the > target and the X-ray beam..."? This still assumes that the area of the > target illuminated by the X-ray beam is perfectly flat. If not, should it > say further "... and the midline of the X-ray beam..."? Pedantic, perhaps, > but it's better to be explicit. In most works I remember reading the take-off angle was small, a few degrees away from zero rather than a few degrees away from 90 degrees. This seems to be the usage required by the definiton you are criticisizing (found by searching on the text of all those e-mails I never read - there were only two concerning _diffrn_source_take-off_angle one from David and one from George). To comply with this usage, you need to substitute <<The angle between the normal>> by <<The complement of the angle between the normal>>. I agree with you that the initial wording was unsatisfactory. One can not define an angle with respect to a plane. > This still assumes that the area of the > > target illuminated by the X-ray beam is perfectly flat. It seems you are also assuming that the electron beam has zero divergence on the target. Unless the persons who suggested this item complain, I would leave out the reference to the midline. I'm not sure what use they are really going to make of the numerical value of _diffrn_source_take-off_angle. H.
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