Knowledge Bank

Careful measurements of pressure broadening in $CO2$ have been made in the $\nu 3$ band. The sample was contained in a 2m long multiple traversal cell set for four transits. The long pathlength allowed very low partial pressures of $CO2$ to be used. The temperature could be set anywhere between room temperature and 200 K and several recordings were made in this range. Nitrogen, oxygen and air (actually mixtures of pure nitrogen and oxygen since laboratory air contained far too much $CO2$) were used as collision partners at pressures up to 200 Torr. The temperature and m dependence of the broadening will be compared with recent theoretical calculations.