Except at very low frequencies, pressure broadening can be removed by working at very low pressures. Likewise, Doppler can be eliminated two ways. One is by using effusive atomic or molecular beams. The other is by Lamb dip Spectroscopy.

thank you Rajib Biswas,

Doppler broadening can be correcte by back ground correction methods?

Except at very low frequencies, pressure broadening may be removed simply by working at a sufficiently low pressure. Doppler broadening may be reduced or removed by either Effusive atomic (molecular beams) or Lamb dip spectroscopy