On the Theory of Spin Relaxation of Gas Molecules: The Strong-Collision Limit

Abstract

A model of spin relaxation of gas molecules based upon an assumption of strong collisions is developed. A relaxation matrix formally similar to that of Redfield, but with different spectral densities, is obtained. The nuclear magnetic relaxation of gaseous orthohydrogen is discussed in terms of these results, and it is shown that, in general, molecules in different J states are expected to exhibit different relaxation times (a conclusion that is independent of the strong collision assumption) whenever the collision mechanism is effective only in reorienting J but not in changing its magnitude. Otherwise statistical averages of relaxation times are obtained. Relaxation of more complex molecules is also discussed.