OPTIMIZED FREQUENCY PHASE-MODULATED BROAD-BAND INVERSION PULSES

A series of composite inversion pulses using coherent frequency switching was shown earlier (T. Fujiwara and K. Nagayama, J. Magn. Reson., 77, 53 (1988)) to provide approximate inversion over broad offset ranges for a spin- 1 2 system. In this paper, we describe improvements of the inversion pulses: the component pulses were divided into shorter rectangular pulses, whose pulse widths, radiofrequencies, and phases were determined with numerical optimization. These pulses are not as smooth as tangential frequency sweeps in time-dependent RF phase. In high-resolution NMR where an RF field is rather homogeneous, these pulses provide more than 99% average inversions with shorter total pulse widths compared with other frequency-sweep and composite inversion pulses. © 1990.