Z‐restored spin‐echo 13C 1D spectrum of straight baseline free of hump, dip and roll

Abstract

A pulse sequence of z-restored spin echo, -pi-beta-tau-pi-tau-, employing a pi pulse in the middle of the delay (2tau) to form a spin echo and the two pi pulses together to restore the residual longitudinal magnetization back to + z direction, is described. (13)C spectra of organic compounds provide a wealth of structural information; however, (13)C 1D spectra acquired using reverse geometry probes can have significant baseline humps or rolls because of pulse ring-down within the coil. The baseline distortions are especially apparent in spectra acquired using cryogenically enhanced probes. The baseline problem may be alleviated by extending the delay between the last pulse and the starting point of acquisition. However, uses of long delay times introduce large negative first-order phase corrections which themselves produce baseline roll. The prescribed experiment can be used to completely remove the hump, roll or dip in the baseline of the (13)C spectrum and at the same time obtain sensitivity similar to the experiment of a single beta pulse. We believe that this experiment will be of general applications in acquiring high-quality (13)C NMR data with reverse geometry probes and spectral interpretation.