Air-broadening coefficients of the HO2 radical in the 2ν1 band measured using cw-CRDS

In this paper we present measurements of the air-broadening coefficients of HO2 at room temperature in the 2ν1 band around 1.5 microns. The HO2 radicals were created by flash photolysis of SOCl2 in a flow of O2/CH3OH mixtures. To observe air-broadening, N2 (79%) and O2 (21%) were added using calibrated flow controllers and a total pressure controller. The total pressure was monitored in parallel using a capacitive pressure gauge. Air-broadening coefficients at 296 K were determined for 34 absorption lines between 6631 and 6671 cm−1. The air-broadening coefficients of HO2 show a rotational dependence (decreasing from about 0.14 cm−1/atm for N″ = 3 to about 0.09 cm−1/atm for N″ = 10). No evidence for collisional narrowing was observed.