loss function

"Loss function" is given by the negative of the imaginary part of inverse of the dielectric function or Im[‐1/ε(ω)], where ε(ω) is the dielectric function. By removing the effect of multiple scatterings from an EELS spectrum, the EELS spectrum only due to single scattering is obtained. Next, the effect of the incident beam intensity and that of the aperture size from the spectrum are removed. And then, when the intensity of the obtained spectrum is normalized, the absolute value of the electron energy loss or the loss function is obtained. The loss function is the most important quantity obtained from EELS. By using Kramers-Kronig equation, the real part corresponding to the loss function is derived. From the real and imaginary parts, the dielectric function of the specimen is calculated. Various physical properties such as refractive index, optical reflectivity, optical absorption intensity etc. can be calculated from the dielectric function.

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