Pressure Narrowing of the Rotational Lines of the Fundamental Infrared Band of H2 in Collision-Induced Absorption

The enhancement by argon of the pressure-induced fundamental infrared absorption band of hydrogen is studied for Ar densities in the range 8–820 amagat at 152 K. The half-width, Δv1/2, of the quadrupole-induced S1(1) transition remains constant at 55 cm−1 up to ~300 amagat and then decreases to 25 cm−1 at the highest density. In the higher density range Δv1/2 varies inversely as the density. The S1(1) line of H2 in liquid H2–Ar solutions shows a similar pressure narrowing for Ar densities in the range 640–833 amagat at 115 K.