Line Intensities and Fluorescence Yield

The intensity of emission of a particular line (say La which is Lni-Mv transition) will depend upon various factors, e.g., (a) the probability that the incident radiation will ionize an atom on the Lm level (b) the probability that the vacant site created on Lm will be filled by an My electron and (c) the probability that the Lai photon will leave the atom without being absorbed within the atom itself (Auger effect). 

Fluorescence yield is one of the major factors that determine the intensities of X-ray spectra. For each excited state of an isolated atom, the fluorescence yield is defined as tUx = Fx/Ftot in terms of the radiative and total transition probabilities F for the particular state (the transition probabilities further depend on the angular momentum quantum number, the number of electrons available for transition as well as the excitation energy). The average fluores- 

Thus the fluorescence yield (cuk) is related to the number of photons emitted in unit time divided by the number of vacancies formed at that time i.e., 

For L- and M-shells comprising of three and five subshells, respectively, if N excited states are produced with population distribution n each having fluorescence yield tu, then the average fluorescence yield for the distribution is given by 

3 Critical Excitation Energies of the Exciting Radiation/Particles 

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