Velocity anisotropy cross section

The heart of the apparatus is the scattering region where a secondary beam crosses the path of the NO molecules in a magnetic field of variable direction. The collision partners possess a well-defined direction of average relative velocity so that the magnetic field can be made parallel and perpendicular to this direction. What is observed is the difference in attenuation of the primary beam for the two orientations of the magnetic field or (translated into cross sections) the anisotropy defined by... 

Here o- (o-x) is the total cross section measured with the magnetic field parallel (perpendicular) to the direction of the average relative velocity total cross section 8-083 (2eR%Jhv)215. As shall be discussed in Section V the anisotropy A can be split into a glory and a non-glory contribution, in first order d.w.a. 

The most striking change is in the A-term that accounts for multipath dispersion (Equation [3.33] in the van Deemter theory) and decreases rapidly with decreasing i.d. This effect was interpreted (Karlsson 1988) as reflecting a decrease in the extent of the flow rate variation over the column cross-section as the i.d. decreases, together with shorter time for solute molecules to diffuse radially through the flow velocity profile (parabolic in the case of a nonpacked column) together these phenomena will decrease the effect of flow anisotropy that is reflected in... 

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