Figure 2

The ‘EigenVAlue’ (EVA) pseudo-spectrum for the molecule Furan (shown in inset), constructed by broadening the calculated vibrational peaks (stems in red) with Gaussian functions (in blue) of suitable σ (here 100 cm⁻¹) and summing up the contributions from all of them at each frequency point. (b) The EVA pseudospectrum, of Furan Methanethiol (inset) as an example, with the partitioning of the frequency scale by types of vibrational modes. From left to right: Torsional modes, Ring Torsion and C–H rocking, Ring Deformation, C–H wagging, C–C stretch, C=C stretch, C=O stretch, S–H stretch, C–H stretch. Similar broad classification of modes can be done so the entire convolved EVA spectra can be deconvolved into broad peaks to identify the regions. This suggests the classification of odorant molecules by broad separation of the vibrational spectrum into these regions, accomplished through the ‘peak-decomposed EVA’. (c) Peak Decomposition of the EVA spectrum of Furan (shown in inset). (d) Construction of the Peak-Decomposed EVA (PD-EVA) spectrum by following the same procedure as for EVA (illustrated in (a))