Nuclear-spin-lattice relaxation times forH2in solid nonmagnetic hosts

Abstract

We calculate the nuclear-spin relaxation times $T_1$ and $T_2$ for isolated ortho ($J=1\mathrm{}$) ${\mathrm{H}}_2$ molecules in solid nonmagnetic hosts located at sites with various crystal fields. The mechanism considered for the relaxation of a nuclear spin to lattice equilibrium proceeds via the molecular angular momentum and is valid in the limit where molecular spin-lattice decay rates are much greater than molecular-nuclear-spin coupling frequencies. We find that many relaxation properties, including the value of $T_1$ at the $T_1$ minimum and the product of $T_1{T}_2$ at temperatures well below the temperature of the $T_1$ minimum, depend crucially on the crystal field at the ${\mathrm{H}}_2$ molecular site. Thus measurements of $T_1$ and $T_2$ can yield definite information about the environment of ${\mathrm{H}}_2$ molecules in a host lattice.