Absorption laws, 4-2. Oscillator strength

Direct calculation of extinction coefficients (and hence oscillator strengths) requires a knowledge of both intensity of absorption and concentration of absorbing species. For the transition described above, concentrations of OH were calculated from the known fractional dissociation of water at elevated temperatures. In a few other instances, it may be possible to estimate the concentration of the intermediate from chemical considerations. Thus, Lipscomb et alP were able to calculate the extinction coefficient at A = 2577 A of the radical CIO from flash photolysis studies of chlorine dioidde. It was shown that the disappearance of CIO obeyed a second order rate law, so that... 

The oscillator strength can be evaluated also from the observed absorption spectra, using Lambert-Beer s law, where e is the molar extinction coefficient given in M cnr. ... 

In Chapter 8, we characterized the strengths of one-photon transitions in terms of Einstein coefficients and oscillator strengths. According to Beer s law, a weak light beam with incident intensity 7o will emerge from an absorptive sample of concentration C and path length I with diminished intensity I = Iq exp(—aC/), where a is the molar absorption coefficient. Beer s law can be recast in the form... 

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