Broadband excitation pulses with variable RF amplitude-dependent flip angle (RADFA)

Abstract

Pulse sequences in NMR spectroscopy sometimes require the adjustment of effective flip angles with respect to experiment-specific or sample-specific parameters. Here, we present a quality factor for efficient optimization of offset-compensated broadband excitation pulses with RF amplitude-dependent effective flip angles (RADFA). After proof of principle, physical limits of RF amplitude-restricted and RF power-restricted broadband RADFA pulses are explored and corresponding pulse shapes and performances characterized in detail.

Keywords: Ernst angle; broadband pulse; excitation pulse; optimal control theory; variable flip angle.