THE EFFECT OF SPIN DECOUPLING ON LINE-SHAPES IN SOLID-STATE NUCLEAR-MAGNETIC-RESONANCE

Experimental and theoretical aspects of carbon-13 line shapes in stati c solids are described for on-resonance spin decoupling conditions. A relatively simple theoretical approach is provided for describing line shapes in static solids based on an operator representation of static second-order perturbation theory and theoretical line shapes in I2S a nd InS systems are calculated. The line shapes are predicted to compri se a single center line and ''decoupling sidebands'' on each side of t he center line which move outward and diminish in amplitude as the dec oupling field is increased. The predicted behavior is confirmed by exp eriments on an isolated seven spin system, where the decoupling sideba nds are observed directly, and some organic solids in which the decoup ling sidebands are not observed directly but in which their presence c an be deduced from the behavior of the center line. A comparison is ma de between the theoretical predictions based on a complete quantum mec hanical treatment and the predictions made using classical approximati ons in the model for the line shape. We conclude, based on our experim ental results, that the line shape has a character which reflects the quantum nature of the spin system, even it? organic solids, and that o n-resonance terms appear to dominate experimental line shapes. (C) 199 6 American Institute of Physics.