Varian Associates, Inc.

Steven L Patt

Stephen H Smallcombe

Paul A Keifer

Observation of transient phenomena in an oversampled regime is implemented with a time correction obtained by prepending one or more pseudo datums to the oversampled data to constitute an effective negative delay for the oversampled data set including the pseudo datums. For an oversampling factor N and oversampling rate .omega..sub.s, a digital filter furnishes downsampled data uniformly spaced in time by N/.omega..sub.s and positioned at n (N/.omega..sub.s) where n is the discrete downsampled time coordinate.

Time correction for digital filters in transient measurments

Improved solvent suppression in NMR data is achieved using pulse sequences wherein each of a series of selective excitation pulses are followed by a magnetic gradient pulse and a delay, where the magnetic gradient pulse amplitudes monotonically decrease by a selected fraction of the preceeding gradient pulse. Decoupling a second nucleus during selective excitation pulses has been shown to be efficacious for suppression of organic solvents.

Solvent suppression method for LC-NMR and high-resolution-NMR

Compensation rather than direct suppression removes the effects of acoustic ringing as encountered in pulsed nuclear magnetic resonance experiments. Single and double spin-echo excitation, combined with several alternative schemes for phase cycling both transmitter and receiver, is one type of compensatory technique. Another technique consists of acquiring free induction decay signals in pairs, with the second preceded by an inversion pulse a short time prior to the normal excitation pulse, and with the second acquisition acquired subtractively, assuring phase coherence of the signals and phase opposition and hence cancellation of the acoustic ringing. Phase cycling of the inversion pulse may also be employed in the latter technique to suppress acoustic ringing stimulated by the inversion pulse.

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Cupertino, CA, United States of America

Steven L Patt