INVESTIGATING CATALYTIC PROCESSES WITH PARAHYDROGEN - EVOLUTION OF ZERO-QUANTUM COHERENCE IN AA'X SPIN SYSTEMS

A systematic outline for the elucidation of the nature of hydrogenatio n intermediates with a lifetime too short to be directly detectable wi th standard NMR methods is presented. The method takes advantage of th e special nature of the parahydrogen density operator and its inherent enhancement factor. The key aspect of these experiments is the evolut ion of zero-quantum coherence which is contained in the parahydrogen d ensity operator. Analytical coherence transfer functions have been der ived which describe the evolution of this zero-quantum coherence in sp in systems consisting of three spins 1/2 that form an AA'X spin system . The analytical expressions presented form a basis for a thorough inv estigation of crucial catalytic steps. (C) 1998 Academic Press.