Total widths, size dependence

Convergence Considerations and Approximate Methods. Another consi-deration which bears on the reliability of results such as those presented above is the question whether or not the calculations are really fully converged. For the prototype (n,Jl,v, j, J)=(0,0,1,0,0) level of H2-Ar, this question is examined in Tables VI and VII, which show how the partial and total widths depend on the size of the angular basis set used for the v l and v" 0 levels, respectively. The calculations of Table VI used a fully-converged open... 

The size dependence of the total widths has been studied by several theoretical groups [8, 37, 40, 59-61]. The jellium model was used nearly exclusively. In this case, the interband decay of the plasmon discussed above is not possible, and the collective plasmon oscillations can only decay by exciting a single electron from the same band — a process that has been termed Landau damping . For sufficiently large clusters this gives (Equation 9.7 of Ref. [37]) a width like... 

Equation 16 shows that the peak variance or band broadening is comprised of individual contributions from different aspects of the separation process. The first term in equation 16 represents the contribution of the width of the feed band to the peak variance. The second term represents the contribution to band broadening from dispersion due to eddy diffusion. The third term represents the contribution of mass transfer effects external to the particles while the fourth term represents the contribution of diffusional resistances within the stationary phase. The significance of each term relative to the total variance depends upon the operating parameters, the column and packing dimensions and the size of the solute. 

The largest elution volume in size-exclusion chromatography is the total mobile-phase volume in the column the sum of the pore volume and the interstitial volume, thus the separation space is constrained. Therefore, how good a separation can be obtained depends strongly on the width of the individual band, namely, on the plate count. System plate count is very important in SEC. 

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