Proton Spin Relaxation in Aqueous Solutions of Paramagnetic Ions. II. Cr+++, Mn++, Ni++, Cu++, and Gd+++

Abstract

Nuclear magnetic relaxation times for protons in dilute aqueous solutions of chromic, manganous, nickel, cupric, and gadolinium ions were measured in the frequency range 1.9 to 60 Mc/sec. Results were interpreted in terms of Solomon's formulation of electron-nuclear dipole-dipole interaction and Bloembergen's expression for scalar coupling of electron and nuclear spins. In large magnetic fields relaxation times were found to be shorter than those expected on the basis of low field values, suggesting that the effective ion magnetic moments, electron spin relaxation times, and/or electron-nuclear spin exchange constants are field-dependent.