Theoretical study of nuclear-spin-lattice relaxation in solid H2

Nuclear-spin-lattice relaxation in solid mixtures of ortho and para hydrogen is studied as a function of the o-H2 concentration c. Equations of motion for the dynamical two-point angular momentum correlation functions are first obtained by the method of Blume and Hubbard. These equations are then impurity averaged by the Sung-Arnold method to obtain equations valid in the low-c regime. Numerical solutions to the latter equations are then used to obtain the nuclear-spin-lattice relaxation time T1 as a function of c. The resulting T1 displays the experimentally observed c53 behavior at small c and its magnitude is shown to agree favorably with experiments at 10 K over the concentration range 0≤c≤0.5.