Near-infrared energy

There are multiple types of molecular vibrations that absorb at unique wavelengths or frequencies of near-infrared energy depending upon the bond type. Several normal (or normal mode) types of molecular vibrations active within the NIR region are illustrated in the following figures. Each of these types of vibrations has a unique frequency where absorption occurs. The location of these frequencies and the associated molecular structures (spectra-structure correlations) are the purpose of this book. 

Another method, called photobleaching, works on robust soHds but may cause photodecomposition in many materials. The simplest solution to the fluorescence problem is excitation in the near infrared (750 nm—1.06 pm), where the energy of the incident photons is lower than the electronic transitions of most organic materials, so fluorescence caimot occur. The Raman signal can then be observed more easily. The elimination of fluorescence background more than compensates for the reduction in scattering efficiency in the near infrared. Only in the case of transition-metal compounds, which can fluoresce in the near infrared, is excitation in the midvisible likely to produce superior results in practical samples (17). 

The triruthenium derivatives 31-35 show characteristic intracluster charge transfer (IC) absorptions in the visible to near-infrared region (600-1000 nm) and cluster-to-ligand charge transfer (CLCT) transitions at 320-450 nm. Compared with the low energy bands in [Ru3n m m]+ complexes 31-35, those in the one-electron reduced neutral [Ru3 ]° species are remarkably red-shifted. The decrease in energy for these transitions by one-electron reduction reflects a rise of the occupied d% levels as the number of electrons increases. Complexes 31-35 exhibit... 

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