Cross sections for transfer of rotational angular momentum in CO2 from 13C spin relaxation studies in the gas phase

Nuclear spin-lattice relaxation times (T1) have been measured for 13C in 13C16O2 in pure CO2 gas and in CH4, N2, Ar, HCl, Kr, Xe, and SF6 gases as a function of temperature. The relaxation is completely dominated by the spin-rotation mechanism so that empirical values of the cross sections for rotational angular momentum transfer σJ are obtained as a function of temperature. At 300 K the values of σJ/Å2 are 59.9±0.8 (CO2–CO2), 30±1 (CO2–CH4), 26.6±0.8 (CO2–N2), 33.9±0.2 (CO2–Ar), 53.5±0.9 (CO2–HCl), 49±1 (CO2–Kr), 62±2 (CO2–Xe), and 91±3 (CO2–SF6). The temperature dependence of these cross sections in CO2–CO2, CO2–HCl, CO2–Xe, and CO2–SF6 is T−1 as expected, and deviates from T−1 in CO2–CH4, CO2–N2, CO2–Ar, and CO2–Kr.