Novel measurements of nuclear spin cross-relaxation in metal hydrides.

摘要

Recent NMR measurements of proton relaxation have shown an unexpected frequency dependence in several metal-hydrogen systems at low temperatures. An explanation proposed by the Ames group involves cross-relaxation of protons to quadrupolar metal nuclei. We test this hypothesis with relaxation experiments involving large amplitude field modulation. The field modulation sweeps the proton resonance through the distribution of metal frequencies. Thus, the protons come into contact with more metal nuclei, increasing the proton relaxation rate. Relaxation measurements have been performed on several samples and the proton resonance frequency, the modulation frequency, and the modulation amplitude have been varied. Also to be reported are T(sub 1) measurements on slowly spinning samples; the rotation produces periodic variations of metal quadrupolar frequencies.