On the possibility of performing self-calibrated selective pi/2 pulses in nuclear-magnetic resonance

In this paper, a generalization of the concept of selective "slaved" pulses in NMR spectroscopy introduced recently by the authors is presented. The s hape of these pulses is slaved to that of a signal produced by the sample b y the action of an electronic feedback loop. The theoretical analysis is ba sed on results of the theory of nonlinear dynamical systems, which predicts the possibility of performing 90 degrees self-calibrated radiofrequency pu lses, through the simultaneous action of a constant radio-frequency field a nd of a magnetization dependent field of the kind above. Experimental demon strations show that rotation of the magnetization onto the xy-plane is achi eved, regardless of its initial position. Moreover, it is shown to remain s table for more than 50 ms, without significant loss of intensity. (C) 2000 American Institute of Physics. [S0021-9606(00)01213-7].