Light spectroscopic data, plot

Recently, Sapre et al. showed that a plot of the maximum fluorescence of Neutral Red (NR) against the solvent polarity function Af is clearly bilinear (see Figure 10.3.8). Accordingly, they concluded that, in solvents with Af > 0.37, the emitting state changes to a much more polar, ICT state. The analysis of this spectroscopic data in the light of our scales reveals that, in fact, the solvatoehromism of NR is normal, albeit dependent not only on the polarity of the solvent (SPP), but also on its acidity (SA) (see Figure 10.3.9) ... 

A plot of V vs —1/ 2 should be linear, with equal slope and intercept. The most reliable and accurate data available fail this test statistically [24], The discrepancy is not large but significant and reminiscent of the spectroscopic red shift measured in galactic light. The common origin of these discrepancies cannot be a Doppler effect and most likely is due to space-time curvature. 

---