NMR pulse sequence:
MQ-MAS signal enhancement with RAPT

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Rotor Assisted Population Transfer MQ-MAS

Grandinetti and coworkers applied a fast 180° phase alternating pulse train during MAS which can prepare a selectively excited state in which the populations of all states |m> with the same sign of m are equal, resulting in an enhanced central transition polarization of all crystallite orientations in a powder sample during MAS.

The application of RAPT before RIACT(II) improves the sensitivity RIACT(II) experiment by a factor of 1.8 in a spin I = 3/2 system.

RAPT preparation MQMAS sequence

On the other hand, the sensitivity is reduced by a factor of 0.6 when RAPT is applied before conventional MQMAS sequences that draw their coherences from the equilibrium polarization associated with |m = ±3/2> (for example two-pulse MQMAS and FASTER).

A new RAPT scheme uses the remaining polarisation of the satellites to obtain a further improvement of the central transition by performing RAPT enhanced experiments several times. This enhanced RAPT sequence consists of a train of Gaussian pulses with alternating off-resonance frequencies, which allows us to explore a wider range of frequency offsets. Gaussian pulses also improve the selectivity of satellite excitation.

Solid-state NMR bibliography for:

Aluminum-27
Antimony-121/123
Arsenic-75
Barium-135/137
Beryllium-9
Bismuth-209
Boron-11
Bromine-79/81
Calcium-43
Cesium-133
Chlorine-35/37
Chromium-53
Cobalt-59
Copper-63/65
Deuterium-2
Gallium-69/71
Germanium-73
Gold-197
Hafnium-177/179
Indium-113/115
Iodine-127
Iridium-191/193
Krypton-83
Lanthanum-139
Lithium-7
Magnesium-25
Manganese-55
Mercury-201
Molybdenum-95/97
Neon-21
Nickel-61
Niobium-93
Nitrogen-14
Osmium-189
Oxygen-17
Palladium-105
Potassium-39/41
Rhenium-185/187
Rubidium-85/87
Ruthenium-99/101
Scandium-45
Sodium-23
Strontium-87
Sulfur-33
Tantalum-181
Titanium-47/49
Vanadium-51
Xenon-131
Zinc-67
Zirconium-91
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