Extinction spectrum

[krindik]

Hi,

Could somebody pls give details on how extinction spectrum can be calculated. In several books I refered, couldn't find an exact definition. Is this related to extinction coefficient (imaginary part of complex refractive index?)

For example, how can the extinction spectra be calculated when an object is placed in an EM field? (I'm trying to simulate results of a paper. But can't find how they have calculated extinction spectra.)

Can somebody help?

Thanks