Photon models test results

At this stage there is an open question as to whether other radial parts of the generating function, exist being similar to that of Eq. (143) and giving results same as or similar to those just mentioned. Thus the photon model and its internal structure could also be tested in observations of various scattering processes. 

Frequently, values of P for wavelengths where experimental data do not exist are estimated by extrapolation using a two-level model description of the resonance enhancement of P (see Appendix). Levine and co-workers [170] have also shown how to estimate the wavelength (frequency) dispersion of two-photon contributions to p. Because of the potential of significant errors associated with each measurement method, it is important to compare results from different measurement techniques. Perhaps the ultimate test of the characterization of the product of pP is the slope of electro-optic coefficient versus chromophore number density at low chromophore loading. It is, after all, optimization of the electro-optic coefficient of the macroscopic material that is our ultimate objective. 

While new applications of the electron-photon coincidence method, such as zero field quantum beats, will continue the full analysis of the experimental results is complex. The determination of parameters, such as the spin orbit phase parameters e and A, which allow specific dynamical features of theoretical models to be tested will take on a greater significance. For heavy atoms this is of particular significance since there is only limited theoretical results available and effects, such as spin orbit interaction, must be taken into account. Perhaps also the "ultimate" electron impact experiments are starting where polarised electrons are used as the projectile in coincidence experiments. 

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