Irregular spectrum

Table 3 shows the nonadiabatic levels of B2 symmetry and their absorption intensities between 16000 and 16300 cm l. The equilibrium symmetric-stretch and bending coordinates of the electronic species are different by about 6 and 24%, respectively [17], whereas the antisymmetric stretch is equal. Therefore, the conical intersection preferably couples a2B2(vi,v2,0) combination states with their X Ai partners, but this interaction is perturbed by the A B2 antisymmetric-stretch species. Above 15000 cm l, the nonadiabatic intensity distribution is thus modulated by the maxima due to n> states with large A B2 symmetric stretch-bending character, whereas A B2 pure overtones are much weaker (e.g. bands 409 and 415 of Table 3). As the energy increases, these vibronic interactions give rise to a more and more irregular spectrum.

Irregular Spectrum Regular/Irregular Spectrum Regular Spectrum... 

Conceptually, the problem of going from the time domain spectra in Figures 3.7(a)-3.9(a) to the frequency domain spectra in Figures 3.7(b)-3.9(b) is straightforward, at least in these cases because we knew the result before we started. Nevertheless, we can still visualize the breaking down of any time domain spectrum, however complex and irregular in appearance, into its component waves, each with its characteristic frequency and amplitude. Although we can visualize it, the process of Fourier transformation which actually carries it out is a mathematically complex operation. The mathematical principles will be discussed only briefly here. 

Now let us look at the NOESY spectrum (b) just as in COSY, we can identify a diagonal and a series of associated off-diagonal cross peaks. Thus the interpretation of the results is analogous to the method we have already learned for COSY. However, the cross peaks are not due to spin-spin coupling but to NOE effects between the protons concerned. However, if we look more closely we can see one big difference between the diagonal peaks, which look like irregular circles, and the cross peaks, which look just like all the peaks in the COSY spectrum. 

Spectrum of N02 Some Insights into the Causes of Its Irregularity. 

Despite the difficulty cited, the study of the vibrational spectrum of a liquid is useful to the extent that it is possible to separate intramolecular and inter-molecular modes of motion. It is now well established that the presence of disorder in a system can lead to localization of vibrational modes 28-34>, and that this localization is more pronounced the higher the vibrational frequency. It is also well established that there are low frequency coherent (phonon-like) excitations in a disordered material 35,36) These excitations are, however, heavily damped by virtue of the structural irregularities and the coupling between single molecule diffusive motion and collective motion of groups of atoms. 

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