Composite pulse excitation in three-level systems

Abstract

It is demonstrated by theory and experiment that it is possible to excite coherence uniformly in three-level systems with a wide range of anharmonicities by using a composite pulse excitation method. The theory is based on a formal analogy between the anharmonic three-level case and the simpler system with equally spaced energy levels where composite pulse techniques are already well known to compensate for the effects of mismatch between photon energies and level separations. Computer simulations and solid-state NMR experiments on the three-level system of deuterium (spin 1) verify the uniformity of the excitation. The NMR powder spectrum of deuterated polymethylmethacrylate is faithfully reproduced even using a radio-frequency (rf) field strength weaker than the quadrupole interactions.