Optimized phases for the acquisition of J -spectra in coupled spin systems for thermally and PHIP polarized molecules

BUSSANDRI, S.; PRINA, I.; ACOSTA, R.H.; BULJUBASICH, L.

JOURNAL OF MAGNETIC RESONANCE

ACADEMIC PRESS INC ELSEVIER SCIENCE

Año: 2018 vol. 289 p. 55 - 62

1090-7807

We demonstrate that the relative phases in the refocusing pulses of multipulse sequences can compensatefor pulse errors and off-resonant effects, which are commonly encountered in J-spectroscopy whenCPMG is used for acquisition. The use of supercycles has been considered many times in the past, butalways from the view point of time-domain NMR, that is, in an effort to lengthen the decay of the magnetization.Here we use simple spin-coupled systems, in which the quantum evolution of the system canbe simulated and contrasted to experimental results. In order to explore fine details, we resort to partialJ-spectroscopy, that is, to the acquisition of J-spectra of a defined multiplet, which is acquired with a suitabledigital filter. We unambiguously show that when finite radiofrequency pulses are considered, theoff-resonance effects on nearby multiplets affects the dynamics of the spins within the spectral windowunder acquisition. Moreover, the most robust phase cycling scheme for our setup consists of a 4-pulsecycle, with phases yyyy or xxxx for an excitation pulse with phase x.We show simulated and experimentalresults in both thermally polarized and PHIP hyperpolarized systems.