Narrow resonance approximation density

The results developed above may be used to obtain the first-order estimates for the collision densities mentioned previously in Sec. 10.1c. When the resonances are narrow relative to the average loss in energy due to collisions with fuel nuclei and in addition widely separated, we may use the narrow resonance (NR) approximation ... 

In this section we establish simple model expressions that approximately describe narrow EELS resonances near a critical point in the binary approximation [8]. In this analysis we terminate the correlational series, taking into account only the pairwise contributions (the accuracy of this approximation is increased from the band of moderate densities). We use a Lennard-Jones potential... 

A simulation of such a superposition, using the fine-structure constants of the naphthalene molecule (D/hc = 0.100 cm , E/hc = -0.015 cm , and g = ge), and with a linewidth of AB = 1.2 mT for each component is shown in Fig. 7.13a. The discontinuities in the broad Am = 1 ESR spectrum correspond to the principal-axis orientations Bo u u = x,y,z). They occur because of the high density of resonance-field values in the neighbourhood of the principal-axis directions (compare Fig. 7.4). For B = 0, two of these discontinuities occur at the same place. The Am = 2 spectrum is narrow because the anisotropy of the Am = 2 transitions is to first approximation zero. The ESR signal (Fig. 7.13b) is - as usual in ESR due to the method of measurement - the first derivative of the spectrum (absorption vs. frequency or field strength. Fig. 7.13a). Even with a powder or a glass sample. 

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