Nuclear spin-lattice relaxation times for mixtures of ortho- and para- H 2 . II. Low ortho- H 2 </mml…
1989; American Physical Society; Volume: 39; Issue: 10 Linguagem: Inglês
10.1103/physrevb.39.6325
ISSN1095-3795
Autores Tópico(s)Atomic and Subatomic Physics Research
ResumoWe study the longitudinal relaxation time ${T}_{1}$ for the nuclear spins of ortho-hydrogen molecules in a para-hydrogen or a hydrogen deuteride (HD) matrix. Phonon-driven molecular reorientations give rise to both a temperature- and concentration-dependent modulation to the electric-quadrupole-quadrupole-induced electric-field-gradient couplings at ortho sites and provide an important mechanism of nuclear spin-lattice relaxation for experimentally accessible concentrations and temperatures. The well-known ${c}^{5/3}$ law for ${T}_{1}$ is recovered for the ortho-para system. We calculate explicit distributions of relaxation rates as a function of concentration, temperature, and magnetic field. These functions are then applied to ortho and para mixtures and HD. For both systems we find satisfactory agreement with experiment, including temperature and concentration dependence that has been previously unexplained.
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