A NEW EXCITATION SEQUENCE TO OBSERVE THE PASADENA EFFECT

In recent years, a new NMR technique called parahydrogen-induced polar ization (PHIP) has been developed to study homogeneous catalytic hydro genations in situ. This method uses parahydrogen as a reagent and olef ins or acetylenes as the substrates, leading to a large signal enhance ment in the resulting proton spectra. Until now, in order to observe s uch enhanced proton spectra, a 45 degrees pulse was required for acqui sition, but in this paper, there is introduced a simple selective exci tation and detection scheme which provides a more versatile and flexib le means for observing signals enhanced by the PHIP technique, As exam ples, how a 1D TOCSY experiment and how a multistage selective HOHAHA polarization transfer can be performed on a PHIP system are illustrate d. (C) 1996 Academic Press, Inc.