An intercomparison of measured pressure-broadening, pressure shifting parameters of carbon dioxide and their temperature dependence

Abstract

An intercomparison of measured pressure-broadening and pressure-shifting coefficients for carbon dioxide absorption lines was done. The work focuses on collision systems where a significant number of data can be found (CO2–N2, CO2–O2, CO2–air, and CO2–CO2) and yield information important to applications related to Earth's atmosphere. The literature was searched for measured line shape parameter data for the collision systems mentioned above. Databases were created for each perturbing gas with the ro-vibrational transition as the key. Using these databases intercomparisons of the measurements of half-widths, their temperature dependence, and line shifts were made. The data allow the investigations of trends in the data with respect to the vibrational and the rotational quantum numbers, various line shape models, and isotopologue effects.The data were averaged and an estimated uncertainty determined. The averaged data sets are evaluated with respect to the need of the spectroscopic and remote sensing communities. In general many data points do not agree within the stated uncertainty estimate independent of the broadening species. Agreement between measurements of the temperature dependence of the half-width is in a poor state and the understanding of the temperature dependence of the line shift is in its infancy. The intercomparison data show more measurements are needed for the CO2–O2, CO2–N2 and CO2–CO2 systems. In addition to the half-width at 296K, data are needed for the temperature dependence of the half-width and line shift.