In an electron-phonon system the electron-phonon interaction spectral density, α2F(ω), is approximately equal to W(ω) defined as:
α2F(ω)≈W(ω)=(1/2π)d2[ωRe(σ-1(ω))]/dω2 (1)
Where, Re(σ(ω)) is the real part of the optical conductivity. For the electron-spin interaction systems this relation could be converted to I2χ(ω)≈W(ω), where I is the coupling constant of electron-spin interaction and χ(ω) is the imaginary part [...]
