Spin—Lattice Relaxation in Dilute Gases. I. Proton Relaxation in HCl, HBr, and HI

Abstract

Proton spin—lattice relaxation times have been measured in gaseous HCl, HBr, and HI as a function of temperature and pressure in the dilute-gas region. The observed temperature dependence is consistent with that expected for relaxation dominated by a spin—rotation interaction. Effective cross sections for the transfer of angular momentum to molecular rotation during collisions are deduced. The cross sections are large, indicating the importance of the long-range forces between the molecular dipole moments.