The greenhouse gas carbon dioxide gives rise to a strong dip in the atmospheric infrared transmission spectrum at a wavelength of 4.3 um due to excitation of asymmetric stretch vibrations of the CO2 molecule. The peak absorption coefficient for this optical transition's 0.8 m', the oscillator strength is 0.5 and the full width at half maximum of the absorption line is 160 cm' at sea level. Use the Lorentz oscillator model to estimate the concentration of CO2 at sea level in parts per million. Make clear all assumptions and approximations that you use. The density of air at sea level is 1.2 kgm³ and the mass of C and O atoms are 12 and 16 amu respectively.(6)

Fig: 1