Variable angle correlation spectroscopy

The separation of isotropic and anisotropic parts of spectra with heavy overlapped systems is still a challenge for SS NMR spectroscopy. There are several approaches that can allow this goal to be achieved. Pines and co-workers introduced variable angle correlated spectroscopy (VACSY), for instance, and... 

M.A. Eastman, G.A. Barral, A.J. Pines, Variable-angle correlation spectroscopy in solid-state nuclear magnetic resonance, J. Chem. Phys. 97 (1992) 4800-4808. (d) A-C. Kolbert, R.G. Griffin, Two-dimensional resolution of isotropic and anisotropic chemical shifts in magic angle spinning NMR, Chem. Phys. Lett. 166 (1990) 87—91. 

Exchange correlation spectroscopy (E. COSY), a modified form of COSY, is useful for measuring coupling constants. The pulse sequence of the E. COSY experiment has a mixing pulse )3 of variable angle. A number of experiments with different values of /3 are recorded that eliminate the multiplet components of unconnected transitions and leave only the multiplet components for connected transitions. This simplified 2D plot can then be used to measure coupling constants. 

Malvern System 4700 comprises a variable angle spectrometer with computer controlled automatic operation, combining photon correlation spectroscopy and angular intensity measurements with full Mie theory calculations to give accurate size distributions in the 1 nm to 5 pm size range. 

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