Improved broadband inversion performance for NMR in liquids

New NMR broadband inversion pulses that compensate both for resonance offse t and radiofrequency (RF) inhomogeneity are described. The approach describ ed is a straightforward computer optimization of an initial digitized wavef orm generated from either a constant-amplitude frequency sweep or from an e xisting composite inversion pulse. Problems with convergence to local minim a are alleviated by the way the optimization is carried out. For a given du ration and maximum allowable RF field strength B-1 (but not necessarily giv en RMS power deposition), the resultant broadband inversion pulse (BIP) sho ws superior inversion compared to inversion pulses obtained from previous m ethods, including adiabatic inversion pulses. Any existing BIP can be syste matically elaborated to build up longer inversion pulses that perform over larger and larger bandwidths. The resulting pulse need not be adiabatic thr oughout its duration or across the entire operational bandwidth. (C) 2001 A cademic Press.