A high power rectangular RF pulse is used when strong excitation of nuclear spins is required. Parameters that must be specified for a rectangular RF pulse include transmit attenuation, transmit gain, RF gain, reference amplitude, and RF levels. These parameters control the strength and duration of the radiofrequency pulse in order to achieve the desired spin excitation for an experiment. Distorted baselines in NMR spectra can arise from real NMR signals that are wider than the observation window or from instrumental issues like digitizer overload, receiver overload, acoustic probe ringing, or imperfect water saturation.