N2-, O2- and He-collision-induced broadening of sulfur dioxide ro-vibrational lines in the 9.2 μm atmospheric window

Abstract Sulfur dioxide (SO 2 ) is a molecule of considerable interest for both atmospheric chemistry and astrophysics. In the Earth’s atmosphere, it enters in the sulfur cycle and it is ubiquitous present in polluted atmospheres, where it is responsible for acid rains. It is also of astrophysical and planetological importance, being present on Venus and in interstellar clouds. In this work the collisional broadening of a number of ν 1 ro-vibrational lines of SO 2 perturbed by N 2 , O 2 and He are investigated at room temperature in the 9 μm atmospheric region by means of high resolution tunable diode laser (TDL) infrared spectroscopy. From N 2 - and O 2 -broadening coefficients, the broadening parameters of sulfur dioxide in air, useful for atmospheric applications, are derived as well. From the present measurements some conclusions on the quantum number dependence of the N 2 -, O 2 - and He-broadening coefficients are drawn. While the J dependence is weak for all the perturbers investigated, different trends with K a are reported. N 2 -broadening coefficients show a slight decrease with increasing values of K a , whereas O 2 and He broadening cross sections first increase up to K a ″ ≈ 6 and then they keep a nearly constant value. A comparison and a brief discussion on the efficiency of self-, N 2 -, O 2 - and He-collisional dynamics are given. The data obtained represent a significant analysis on foreign broadening of SO 2 useful for atmospheric remote sensing and astrophysical applications.