Atomic Reference Scale for Chemical Shifts of Rubidium

Abstract

Abstract With a multi-nuclei Fourier transform NMR spectrometer the ratio of the Larmor frequencies of 85Rb and 2H in a solution of RbCl in D2O has been measured with high accuracy. The concentration dependence of the 85Rb NMR signals has been determined in solutions of rubidium salts in H2O and D2O. Using this dependence, the ratio of the Larmor frequencies of the 85 Rb nuclei for infinite dilution relative to 2 H in pure D20 is given. From this a gI-factor for 85Rb has been derived and has been compared with the gI-factor of an optical pumping experiment. The difference in the gI-factors results from the shielding of the rubidium nuclei by the water molecules around the ions. The shielding constant is σ(85Rb+) = -2.11 (2) · 10-4 . This yields a general atomic reference scale for the chemical shift of rubidium in the liquid and solid states and the possibility of comparing experimental and theoretical shielding constants.