A comparison of ω and 2θ scans for integrated intensity measurement

Abstract

To maintain intensity measurements on a fixed scale an identical and constant spectral distribution must be integrated in either the (o or 20 scan. Both the vertical and horizontal dimensions of the detector aperture are critical for either scan. With the mechanical arrangements currently in use for upper level o~ scans both aperttwe dimensions are dependent on the mosaic spread of the crystal as well as the spectral dispersion. The optimum type of scan for a given set of conditions is that which yields the true integrated intensity plus the least amount of thermal diffuse scattering. This will be the scan which defines the smallest illuminated volume in reciprocal space. When other factors, such as anomalous dispersion, are equal, a long characteristic wavelength is desirable in that it will give rise to a smaller illuminated volume at a given point, in reciprocal space than will a short wavelength.

A Guide to the Determination of Operational Parameters in the Conventional X-ray Diffractometry of a Small Single Crystal

“…Earlier workers proposed that the estimate of B should be based on the separation of the al and a2 components plus contributions based on the 'natural' widths of the al and a2 components, scaled by an arbitrary factor k (see Burbank 1964;p.436). Numerical estimates derived for Cu and Mo radiation on the basis of these proposals are given in Table 2 and compared with the approach taken in this paper.…”

“…Moreover, the decision as to the magnitude of the wavelength-dispersive component of these parameters, where relevant, does not always appear to be related to the physical features of the experiment. 0004-9506/84/010000$02.00 In the earlier literature (Furnas 1957;Alexander and Smith 1962, 1964a, 1964bBurbank 1964Burbank , 1965Ladell and Spielberg 1966;Kheiker 1969;Werner 1972;Einstein 1974;Denne 1977a), the situation was analysed largely in terms of a onedimensional presentation of the reflection profile. Apart from the suggestions of Furnas (1957) and Alexander et ale (1963), it was not very clear from the theoretical studies how an experimentalist should.…”

Metal complexes in detergent analysis: the crystal structure of bis (ethylenediamine)bis(dodecylsulphato)copper(II)

“…Space group P1 was confirmed by solution of the structure. A needle-shaped fragment of a crystal (0-08 x 0.12 x 0.66 mm) was used for the measurement of intensity (Burbank, 1964). The vertical detector aperture was 4 mm and the horizontal aperture was (3.0 + 0.35 tan 0) mm.…”

The crystal structure of the anti-tumor agent 5-(3,3-dimethyl-1-triazenyl)imidazole-4-carboxamide (NSC-45388)

“…Diffraction data were recorded on an EnrafNonius CAD-4/F automatic diffractometer using Profile analysis of a representative reflection indicated that the conditions for the measurement of integrated intensities would be optimized by o9-(S)20 scans, where S = ½. The to-scan angle and the horizontal counter aperture, both reduced as much as possible so as to minimize the effect of thermal diffuse scattering (Burbank, 1964), were (1.5 + 0.35 tan 0) ° and (1.8 + 0.35 tan 0) mm, respectively. The scan speeds were determined by a required precision tr(/) < 0-005I, subject to a maximum scan time of 180 s per reflection.…”