Photon absorption depth profile

AES Auger electron spectroscopy After the ejection of an electron by absorption of a photon, an atom stays behind as an unstable Ion, which relaxes by filling the hole with an electron from a higher shell. The energy released by this transition Is taken up by another electron, the Auger electron, which leaves the sample with an element-specific kinetic energy. Surface composition, depth profiles... 

The depth-profile of photon absorption is analogous to that for UV-visible light, i.e. I = Io exp(-Ad), where the mass energy absorption coefficient, u/g is used instead of the extinction coefficient. Particulate energy absorption can be described by relative stopping powers. 

Once the light attenuation profile is known, the illuminated fraction y can be obtained (Comet et al, 1994 Takache et al, 2010). The illuminated fraction y is given by the depth of culture Zc where the value of specific rate of photon absorption for compensation A zc) =Ac is obtained, with being the minimum value required to obtain net positive photosynthetic growth (J02 = for =Ac in Eqs. 6 7). In the case of cultivation systems with one-dimensional light attenuation, we obtain ... 

To explain the difference between the 248- and 308-nm irradiation some properties of the polymer and laser at the two irradiation wavelengths must be discussed. At 248 nm the penetration depth of the laser is about 150 nm, whereas for 308 nm the penetration depth is only 60 nm. In addition, the photon energy at 248 nm is 5 eV as compared to the 4 eV at 308 nm. This is one of the reasons why the quantum yield (QY) of photolysis in solution for 248 nm is higher (1.5%) than for 308 nm (0.22%) [120]. A closer inspection of the UV spectra (Fig. 10) reveals that 248 nm is at a minimum of the absorption curve. Assuming a Lorentzian profile for the different absorption bands, it is obvious that an irradiation with 248 nm can lead to a direct excitation of the absorption bands below and above 248 nm. 

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