Photochromic systems of dihydroindolizines

Various derivatives of dihydroindolizines with its reversible photoreaction to betaine and the superimposed thermal reaction have been used to test the algorithms. 

A program system called SIDYS using simulation techniques and parameter identification was applied to the absorption data. It includes random search techniques, Rosenbrock strategy, quasi-Newton methods, and lattice search. It runs on a mainframe computer and provides good agreement between simulated and experimental data. On the other hand, it proves that the data of this type of mechanism are not well conditioned and the quality of the evaluation drastically depends on the parameter set chosen [155]. 

Because of small calculation capacity, any evaluation will need more CPU time. Therefore parameter estimation with highly sophisticated algorithms will consume too much time on small computers. The different equations, eqs. (5.127)-(5.130) applying formal integration provide a good tool 

Combined determination of reaction constants and absorption coefficients In many cases the absorption coefficients of the photo-product cannot be determined, since B cannot be isolated in a pure form. For these conditions quite a few methods have been proposed in the literature [156-160]. If the conditions required for these approximations do not fit, the thermal reverse reaction is used to shift the photostationary state by variation of temperature. The possibilities of such an approach are demonstrated by the photoreaction of dihydroindolizines [49,161]. Using eq. (5.119) and the approximation at the photostationary state 

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