Research into selective radiofrequency pulses has been include the repetitive sampling of zero-quantum coherence (4), simultaneous 13 C detection and broadband proton de-mainly confined to questions of design, experimental performance, and practical applications. Although the motion of coupling with only a single central processing unit (5), direct monitoring of signal decay due to B 1 inhomogeneity magnetization vectors during a soft pulse can be predicted theoretically, corroboration through direct measurement of ( 6), and sensitivity enhancement by multiple refocusing of spin echoes (7). the NMR signal has not hitherto been feasible. We show here that the DANTE sequence (1, 2), which can be used Of the many shaped selective pulse schemes in the literature, the E-BURP-2 excitation pulse (8) was chosen as an as an alternative for almost all soft radiofrequency pulse schemes, affords an opportunity to monitor the motion of illustrative example. The DANTE sequence was made up of n Γ
64 segments with 2t Γ
357 ms giving a total duration the nuclear spins in real time during selective radiofrequency excitation. Calderelli et al. (3) have employed this technique of 22.9 ms, and was pulse-width modulated according to the prescription presented in reference ( 8). The hard pulses had to observe the first few points of a free induction signal, information that is normally obscured by the soft pulse.
a constant amplitude gB 1 /2p Γ
5.3 kHz. The observed real and imaginary components of the NMR signal are displayed The modified DANTE selective excitation scheme may be written as a sequence of a large number n of hard radiofre-in Figs. 1 and2, respectively, for an entire family of offsets ranging from exact resonance to {192 Hz in steps of 8 Hz. quency pulses, Note the smooth time development of the signals throughout all these measurements. With the normal spectrometer phase { -t-b(t) -t-Acq.} n ,
[1] adjustments, the imaginary component corresponds to the * On leave from the