https://doi.org/10.1351/goldbook.08404
In nuclear magnetic resonance spectroscopy, one of two equally sized blocks of frequency data \(\pu{90\!^{\circ}}\) out of phase to each other produced by Fourier transformation of the time domain signal.
Note: Usually only the real frequency data is displayed and in simple 1D spectra equates to the NMR signals being absorption mode (in-phase).
See also: imaginary spectrum