Energy bands, relation spectrum

Figure 5 Schematic representation of absorbance of porphyrin compounds in relation to tissue transmittance at various wavelengths (see text). The lowest energy band (Band I) is shown in each case, apart from the porphyrin spectrum (etio type shown) on the left. The transmittance curve refers to a fold of human scrotal sac 0.7 cm thick (Wan, S. Parrish, J. A. Anderson, R. R. Madden, M. Photochem. Photobiol. 1981, 34, 679-681). The broad feature at ca. 500-600 nm is ascribed to haemoglobin (reproduced by permission of the Royal Society of Chemistry from Chem. Soc. Rev. 1995, 24, 19-33).

Let us now turn to the relation between energy bands and the spectrum. For this, see Fig. 4-3, which shows the absorption spectrum for InAs the corresponding energy bands are shown in Fig. 4-4. InAs is convenient for identifying features of the spectrum. 

The photoelectron spectrum consists of a series of bands where the number of electrons (N) is related to their energy ( i ). The energy of the photoelectron depends on the investigated molecule and on the photon energy. Band intensities are determined by the probability of the ionization events which is again a function of photon energy. The number of photoionization events, JV , is given by... 

In (4.25), according to its derivation, the vector k is real. Consequently the eqn (4.25) gives a spectrum of polaritons consisting, in general, of allowed and forbidden energy bands.36 We can also proceed in a different way and express the refraction index n(w, s) defined by the relations... 

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