Collision broadening of CO ₂ transitions in the region of 4.3 µm. Effects of broadening gas (He, Ar and N ₂ ), rovibrational states and temperature

The collision-broadening parameters, b0L, for a number of lines in the Δν3= 1 transitions from the (0000), (0110), (0200) and (0220) vibrational states of 12C16O2 and the (0000) state of 18O12C16O have been measured at room temperature (300K) and with N2, Ar and He as the broadening gases, using a tunable IR diode laser. The values of b0L decrease with increase in the rotational quantum numbers associated with the transition but there is no significant difference in the broadening of lines from different vibrational bands. Measurements of b0L were also carried out at 160 K on lines in the (0001,0000) band. With the changes in b0L(units of cm–1 atm–1) expressed in the form b0L(T)=b0L(T= 298 K)(298/T)n, n= 0.69 ± 0.17 for He, 0.88 ± 0.18 for Ar, and 0.85 ± 0.09 for N2.