1 5N spin-relaxation studies of N2 in buffer gases. Cross sections for molecular reorientation and rotational energy transfer

Nuclear spin-lattice relaxation times (T1) have been measured as a function of temperature for 15N in N2 gas and in CH4, O2, CO, Ar, HCl, CF4, Kr, and Xe. The relaxation is 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. The values of σJ/Å2 at 300 K are 13.6±0.4 (N2–CH4), 14.9±0.4 (N2–N2), 14.7±0.6 (N2–O2), 15.0±0.9 (N2–CO), 15.9±0.8 (N2–Ar), 22.7±0.6 (N2–HCl), 30±1 (N2–CF4), 18.1±0.5 (N2–Kr), and 19.8±0.5 (N2–Xe). For almost all cases, the temperature dependence of the cross section deviates from T−1.