Replacement of the Lorentz law for the shape of the spectral lines in the infrared region

We propose a new phenomenological law for the shape of the spectral lines in the infrared, which accounts for the exponential decay of the extinction coefficient in the high-frequency region, observed in many spectra. We apply this law to the measured infrared spectra of LiF, NaCl, and MgF2, finding good agreement over a wide range of frequencies.