Tunable diode laser measurements of N2- and air-broadened halfwidths: Lines in the (ν4 + ν5)0 band of 12C2H2 near 7.4 μm

Nitrogen- and air-broadened Lorentz halfwidths have been determined for 29 lines in the P and R branches of the (ν₄ + ν₅)⁰ combination band of ¹²C₂H₂ using a tunable diode laser spectrometer. Two tunable diode lasers operating in the region 1250–1380 cm^?1 were used in recording the data. For nitrogen broadening, the measured halfwidths at 296 K decrease from about 0.11 cm^?1 atm^?1 at |m| = 1 to about 0.05 cm^?1 atm^?1 at |m| = 30, where m = J″ + 1 for R-branch lines, m = ?J″ for P-branch lines, and J″ is the lower state rotational quantum number. On the average, the air-broadened halfwidths are 97% of the N₂-broadened halfwidths.