Automated assignment of dense high resolution gas phase spectra using ab initio eigenenergy lists

The typical relative accuracy of the experimental transition frequencies ranges from 10^-5 to 10^-10 but for the transition intensities it is only 10^-2. The relative accuracy of the most accurate ab initio energy levels are 10 to 10 000 times worse than the experimental values but the ab initio transition intensities have accuracies similar to the experimental data []. Even if the ab initio eigenenergies have been successfully labeled with approximate quantum numbers the use of the ab initio eigenenergy list to automatically assign the lines in a dense high resolution gas phase spectrum seems to be impossible. A complete automatic assignment may be still possible in the case of a combined analysis of all infrared emission spectra recorded if the accurate match of line intensities are combined with the approximate match of line position. In such an analysis a single eigenenergy corresponds to the lower or upper level of many transitions. In a current research project I am working with the research group of A. Csaszar (ELTE, Budapest) to implement these ideas regarding the automatic analysis of high resolution spectra. A related problem is the combination of ab initio intensities with accurate high resolution eigenenergies for their use in analytical applications. Our first paper which includes my concepts related to this question has been published in the Nature publication "Scientific Reports".

[1] T. Furtenbacher, P. Arendas, G. Mellau, and A. G. Csaszar

Simple molecules as complex systems

Sci. Rep. 4, (2014).