The peak value of the Lorentzian line shape occurs at the line center, ν ν = ν ν 0 . A line shape function can be normalized so that its value at ν ν 0 is unity; in the case of a Lorentzian we obtain g ( ν ν ) = g ′ ( ν ν ) g ′ ( ν ν 0 ) = ( Γ Γ / 2 ) 2 ( ν ν − − ν ν 0 ) 2 + ( Γ Γ / 2 ) 2 .