MLEV-17 spin-lock composite pulse and phase sequence

4. Acquisition

Time requirement: 30 min

Sample: 3% strychnine in CDCl₃.

Prior to the experiment the attenuator setting needed to give a 90° shaped pulse of a chosen duration has to be determined (see Exp 7.1). Its phase relative to the phase of the spin-lock pulses must be known, and the 90° pulse duration and the attenuation of the spin-lock pulses must also be calibrated (see Exp. 2.9). Run a normal ¹H NMR spectrum of the sample and note the offsets of the protons to be irradiated. You have to set:

td	32 k
sw	10 ppm
o1	on resonance of selected signal. If the software allows offsets for selective pulses, one can also put o1 in the middle of the ¹H NMR spectrum. However, the different phases of the selective pulses at different offsets must be determined.
p1	Gaussian shaped ¹H transmitter pulse, 50 ms length, transmitter attenuation corresponding to 90° excitation [dB]
p2	trim pulse 2.5 ms at power level of spin-lock [dB]
p3	series of composite 180° pulses (90°, 180°, 90°) at power level of spin-lock, typically 90° pulse-width of 40 μs at 12 dB transmitter attenuation corresponding to an effective spin-lock field of ca. 7000 Hz. Total length of spin-lock set to 200 ms by loop parameter of spin-lock sequence.
d1	2 s
ns	8
ds	4