To assess if and how many components are contributing to the spectra, we modelled the spectra using Gaussian band shapes (Figure ). As obvious from the asymmetric band shapes in Na + , K + , and Cs + , two components were necessary for a satisfactory fit to the spectra. However, while in K + the red components were clearly dominating both ν(COester) and ν(COamide) bands, in Na + and Cs + a ratio of between approx. 2:1 to 1:2 is adopted between band indicated in blue and red. This suggests that K + shows a pronounced preference for a single EBn:M z+ species, whereas for Na + and Cs + a mixture of approximately equally prevalent complexes occurs. The latter appears to be also the case in Li + , Mg 2+ or Ca 2+ with several strongly overlapping bands.