ROTATING-FRAME NUCLEAR DOUBLE RESONANCE DYNAMICS: DIPOLAR FLUCTUATION SPECTRUM IN CaF2

A series of rotating-frame nuclear double-resonance experiments is reported in which the NMR of the rare isotope 43 Ca (natural abundance 0.13%) in CaF2 is detected via the observable resonance signal of the abundant l9F nuclei. The technique consists of (1) cooling the l9F dipolar interaction energy reservoir by means of adiabatic demagnetization in the . 43 rotating frame, (2) coupling the rare Ca to this cooled reservoir by means of a rotating magnetic field at or near the 43ca nuclear Larmer frequency, and (3) examining the final state of this reservoir by measuring the "dipolar" free induction **Work supported in part by the National Science Foundation._ *Now at Bell Telephone Laboratories, Incorporated, Holmdel, New Jersey. 'This work was submitted in partial fulfillment of the requirements for the Ph.D. +This work was initiated while the author was a Research Associate at the Physics Department, University of California, Berkeley, California.