Problems with Numerical Simulations of Optical Spectra

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Currently it is frequent to model the optical spectra by the numerical simulations. But this activity is not easy. There are some problems that cause an imperfect overlap of the modelling spectrum with the experimentally obtained spectrum - the spectra are shifted. The non-ideal overlap of the rotational levels is the most distinctive in the higher values of the quantum rotational number. The same effect is observed in the positions of the vibrational band heads. One of the reasons causing this situation is the first approximation, which is used in the equations simulating optical spectra. To the other problems belongs probability of the transition that is given as constant and also the molecular constants whose values are not known exactly and various sources of them indicate different values. To the non-ideal overlap of experimentally and simulated spectrum contribute the approximation of the rotational line's profile - usually by the Gaussian profile and the shape of the apparatus function that causes distortion of the experimentally obtained spectrum. To minimize its influence it is possible to use spectrometers with high resolution or to clarify the experimental spectrum by various methods. Besides the effects cause the inaccuracies between the simulated and measured it is possible to use the calculated spectrum to analysis the experimentally obtained spectrum.

Numerical simulation, optical spectra, modelling, experimental spectra

Šormová, H., Krčma, F.

12. 7. 2004

Cambridge University Press

Cambridge

P3.24

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