Spin counting experiments in the dipolar-ordered state

The dipolar-ordered state (rhoproportional toH(d)) can be prepared from a state of Zeeman equilibrium at high field by adiabatically removing the Zeeman field. It is also possible to produce dipolar-ordered states in the rotating frame using two well-known methods-adiabatic demagnetization in the rotating frame and the Jeener-Broekaert (JB) pulse pair. Using multiple quantum nuclear magnetic resonance techniques, we illustrate the transient dynamics of the spin system following the JB pulse pair and its evolution to a dipolar-ordered state over a period of approximately 60 mus in a single crystal of CaF2 oriented along the [100] direction, and approximately 100 mus when the crystal is oriented along the [110] direction. By encoding the coherence numbers in an orthogonal basis (the x basis) to the Zeeman basis, we show that the dipolar-ordered state is a two spin correlated state. The observed ratio between double quantum and zero quantum coherences in the x basis confirms the presence of the Ii+Ij-+Ii-Ij+ (flip-flop) terms in the experimentally prepared dipolar-ordered state. (C) 2003 American Institute of Physics.