Phase-modulated nutation nuclear quadrupole resonance spectroscopy

FABIAN VACA CHAVEZ; FEDERICO CASANOVA; HECTOR ROBERT; DANIEL PUSIOL

JOURNAL OF CHEMICAL PHYSICS

AMER INST PHYSICS

Lugar: New York; Año: 1998 vol. 108 p. 1881 - 1885

0021-9606

Nutation nuclear quadrupole resonance spectroscopy enables one to determine the asymmetry parameter on powder samples. The method relies on two-dimensional methodology: The first period is the duration of the radio frequency exciting pulse and the second dimension is the free-evolution period of the quadrupolar nucleus. Varying lengths of the radio frequency pulse induce an amplitude modulation of the free-induction decay signals which is characteristic of the anisotropic nutation frequency distribution. Fourier analysis along the first dimension provides a powder nutation line shape that allows determination of the electric field gradient tensor’s asymmetry parameter. We describe the first application of two-dimensional phase-modulated spectroscopy to a quadrupolar nucleus at zero field. It is shown that a phase-modulated variant of the nutation spectroscopy is feasible in the pure quadrupole regime and it provides a gain in the signal-to-noise ratio compared to the amplitude-modulated method.