BIRD pulse cluster

In 1986 Bax and Subramanian [10] proposed the utilization of the discriminatory power of the Bilinear Rotational Decoupling [36] (BIRD) pulse cluster to achieve an even better suppression of unwanted H- C signals (Figure 13). 

At the end of the BIRD pulse cluster the magnetization of protons coupled by a one-bond coupling to a nucleus is on the +z axis, while the magnetization of protons not presenting such a coupling is on the — z axis. 

Figure 6.31. An alternative low-pass filtering scheme employing selective refocusing of 7ch couplings with a BIRD pulse cluster. The 180° X pulses may be replaced advantageously by composite or adiabatic pulses. Ai is set to 1/2 7ch and Alr to 1/2 7ch-...

Figure 13 Proton detected HMQC-COSY experiment [10] using a BIRD [36] pulse cluster...

The BIRD pulse [14] is in fact a cluster of pulses (Fig. 6.12) used as a tool in NMR to differentiate spins that possess a heteronuclear coupling from those that do not. The effect of the pulse can vary depending on the phases of the pulses within the cluster, so we concentrate here on the selective inversion described above. For illustrative purposes, proton pulse phases of x, y, X will be considered as this provides a clearer picture with the vector model, although equivalent results are achieved with phases x, x, —x, as in the original publication. The scheme (Fig. 6.14) begins with a proton excitation pulse followed by a spin-echo. Since carbon-12 bound protons have no one-bond... 

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