An optimal double-magic flip angle for performing the distance measurement REDOR experiment on a spin S=1

作者：Nimerovsky E; Haimovich A; Goldbourt A^*

来源：Solid State Nuclear Magnetic Resonance, 2015, 72: 127-131.

DOI：10.1016/j.ssnmr.2015.08.003

• Magic angle spinning
• NMR
• REDOR
• Quadrupolar spin
• Dipolar interaction
• Distance measurement

Distance measurements between a half-spin and a quadrupolar S=1 spin having a small quadrupolar coupling constant can be performed using the rotational echo double resonance (REDOR) experiment. We derived an analytical expression for the probability of transitions between energy levels resulting from the application of an arbitrary pulse flip angle to the quadrupolar spin and consequently minimized the probability that populations of individual levels do not undergo a spin transition during the pulse. As a result we discovered that if the flip angle of the quadrupolar spin pulse is 109.47 degrees, the maximal re-coupling values are the largest possible and the signal reaches a maximum value of 8/9, larger than in the use of either a 90 degrees pulse or a 180 degrees pulse. In addition, the slope of the initial decay is higher than that of the 90 degrees pulse. The recoupling signal can be modeled by an exact analytical formula in the ideal case and simulations show that the advantage of the 109.47 degrees pulse is preserved when the quadrupolar coupling constant C-Q. has a finite value typical of H-2 and Li-6 spins (up to C-Q similar to 200 kHz). Experimental results on two spin pairs, H-2-C-13 and Li-6-C-13, demonstrate the validity and accuracy of this method.

• 出版日期2015-11