Knowledge Bank

The linewidths and shifts of the fundamental vibration-rotation band of HF-X and HCL-X systems $(X=N2,O2,Air)$ have been calculated at $202\circ$ and $296\circ K$, using the Kolb-Grime-Baranger theory. The calculations include isotropic effects to all orders, use of realistic trajectories (as a modification of straight line trajectories) and explicit velocity averaging. It is found that the major contribution to the linewidths and shift arise from dipole-quadrupole, quadrupole-quadrupole, and vibrationally dependent isotropic dispersion forces. Due to the reduction of the dipole-quadrupole and quadrupole-quadrupole contributions with increasing $|m|$, the widths decrease, with a leveling off at high $|m|$ values, where the dispersion forces dominate. A comparison between the calculated and $measured1$ widths and shifts, which shows good overall agreement, will be given.