Adiabatic mixing in the liquid state

Adiabatic spin inversion has been used in the liquid state very efficiently for decoupling purposes. Here we show that it can also be adapted for spin mixing experiments, such as the TOCSY and clean TOCSY experiment, and is s uperior to previously employed mixing sequences. The main advantage of adia batic mixing sequences over the conventional mixing schemes used in liquid state experiments is an extremely low sensitivity to RF field inhomogeneity and miscalibration of the B-1 field strength. The method is evaluated expe rimentally by comparing results obtained with different mixing schemes in t he basic 2D TOCSY experiment. In addition to higher reliability, adiabatic mixing provides a sensitivity improvement of ca. 20% as compared to convent ional mixing schemes. This is explained by higher signal losses due to RF i nhomogeneity in the experiments employing traditional mixing schemes. More significant sensitivity improvements can be expected in situations where RF homogeneity is traditionally poor, for example, in large volume probes and magnetic resonance imaging experiments. (C) 1998 Academic Press.