Time-convolutionless representation of the correlation function: prescription for experimental determination of the random force correlation function

Tojuyama and Mori's time-convolutionless formalism is employed as a point of departure to derive a relation between the measured intensity of the spectral band and the random force correlation function (g(t),gsup(*)(0)), where (g(t),fsup(*)(0))=0. The last correlation function plays an essential role in the actual theories of line shape. The application of this procedure in various line-shape experiments (NMR, EPR, Moessbauer, IR, Raman, etc.) could, in consequence, allow to make a better intuitive description of the dissipative properties in physical systems. (author)