ABSTRACT
This part of the book essentially consists of some recalls of physical chemistry connected to spectral methods. Recalls concern electromagnetic radiations. They deal with the parameters defining a wave, the photoelectric effect, briefly the failure of classical physics and the Maxwell equations, Bohr’s condition and the future of the excited molecules. Another recall points to a certain confusion that concerns the definition of spectral methods of analysis, that is to say about some terms such as spectroscopy, spectrometry, and spectrophotometry. Some precisions are brought. When recalling three, the limits of the different spectral regions are specified. Then, a brief listing of absorption spectra and a theory concerning them are given. This theory emphasizes the part played by the energy during the phenomenon of absorption, particularly the internal energy that is rather a notion of statistical thermodynamics.
