Nuclear Overhauser effect transient

Bothner-By AA, Stephens RL, Lee J-M. Stmcture determination of a tetrasaccharide transient nuclear Overhauser effects in the rotating frame. J. Am. Chem. Soc. 1984 106 811-813. 

Bothner-By AA, Stephens RL, Lee J, Warren CD, Jeanloz RW (1984) Structure Determination of a Tetrasaccharide Transient Nuclear Overhauser Effects in the Rotating Frame. J Amer Chem Soc 106 811... 

McBrierty and Douglass have studied cross-relaxation between and F spins in poly(vinylidene fluoride) by means of the transient nuclear Overhauser effect. The results provided valuable additional data in support of previous interpretations of relaxation, in particular the measurement of motional frequencies at the hitherto inaccessible frequency of the difference between H and F frequencies (2 MHz). The same authors have used this technique to study compatibility in blends of poly(vinylidene fluoride) with poly(methyl and ethyl methacrylate)s. The cross-relaxation data indicate substantial intimate mixing. 

A pulse interval of 10 s is sufficient to satisfy the spin-lattice relaxation time, T of the methyl group, which is the slowest relaxing nucleus with a Tj of 2 s at 125°C. The number of transients accumulated depended upon the ethylene content and in each case, accumulations are allowed to continue until a satisfactory signal-to-noise ratio was achieved. Each 13C NMR spectrum is recorded with proton noise-decoupling to remove unwanted 13C - IH scalar couplings. No corrections are made for differential nuclear Overhauser effects since these have been shown to be constant for the major resonances in low ethylene - propylene copolymers. ... 

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