Sensitivity enhancement in natural-abundance solid-state 33S MAS NMR spectroscopy employing adiabatic inversion pulses to the satellite transitions

High Field 33S Solid State NMR and First-Principles Calculations in Potassium Sulfates

“…The technique, however, has seen very few applications, with just over 10 publications on the subject being produced in the past 25 years. [5][6][7][8][9][10][11][12][13][14][15][16] The problem arises mainly from the great difficulty in obtaining the spectra. The only magnetically active isotope, 33 S, has a low natural abundance of 0.75%, and is a spin 3/2 quadrupolar nucleus with rather small magnetogyric ratio γ (absolute resonance frequency Θ ) 7.676 MHz).…”

Testing the sensitivity limits of 33S NMR: An ultra-wideline study of elemental sulfur

“…Considering each of these factors, it is perhaps not surprising that the number of published solid-state NMR studies utilizing this nucleus is so small [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. However, after getting off to a very slow start during the 1980s and 1990s [1][2][3], 33 S solid-state NMR seems to be finally gaining some popularity as a useful and informative probe of the structural environment in sulfur-containing compounds [4][5][6][7][8][9][10][11][12][13][14]. This is mainly due to the increasing availability of high field NMR spectrometers (>14.1 T), which reduce the second order quadrupolar broadening of the central (1/2 M À1/2) transition (CT) as well as providing an increased Zeeman polarization.…”

“…The first application of 33 S MAS NMR to non-crystalline materials was a study of isotopically enriched sulfur-doped silicate glasses of geological interest [5], in which the sulfur environments were shown to be sulfate-like by virtue of the observed chemical shifts. Since then, 33 S MAS NMR has been used to study mineral phases such as ettringite [7,9], tetrathiometallates [8], and other systems [6,[10][11][12][13][14]. Other methodological improvements have also been made.…”

“…MAS has been demonstrated to be useful for measuring small C Q values via the satellite transitions (STs) [6], as well as for studying chemical shielding anisotropy (CSA) [8]. Signal enhancement techniques such as QCPMG [15] or population transfer experiments (which transfer polarization from the STs to the CT [16]) have been used to boost the signal and reduce experimental times significantly [9,10,[12][13][14]. Finally, much larger C Q values have recently been observed from transition metal disulfides [11] and potassium sulfate phases [14] using a combination of high magnetic field strengths, QCPMG enhancement and the ''frequency stepping" method, in which the broad spectra are acquired in a number of separate sections whose widths are determined by the excitation bandwidth of the pulse sequence used.…”

Solid‐state natural abundance 25Mg NMR studies of Na2MgEDTA·4H2O—a possible new reference compound for 25Mg NMR spectroscopy

“…In the case of the adiabatic pulses, the use of either a single pulse or two pulses symmetrically placed around the central transition led to the same result. [14,15,34] These values found for the signal-enhancement factors are somewhat below the theoretical limit expected for a quadrupolar nucleus with half-integer spin in the case of saturation of all satellite transitions (this limit is equal to I + 1/2 for a nucleus with spin I, which means 3.0 for 25 Mg). A larger enhancement factor of 2I (or 5.0 in the case 25 Mg) would be attained in the case of perfect inversion of the satellite transitions in a definite order (first the outer ones, then the inner ones).…”