Chemical shift anisotropy amplification with high amplification factor and improved sensitivity

An improved version of the recently proposed chemical shift anisotropy amplification experiment is described. The original experiment correlates a fast magic angle spinning spectrum in the ω2 dimension with a sideband pattern in ω1 in which the intensities mimic those for a sample spinning at a fraction of the rate ωr/N. Advantages of the experiment include the use of standard methods to extract the principal tensor components from the ω1 sideband patterns and the small number of t1 increments required. The improved version described here permits large amplification factors N to be obtained without resort to prohibitively long sequences of π-pulses and allows sensitivity to be maximized by eliminating the need to store the magnetization along the z-axis for t1. Amplification factors up to 32 are demonstrated experimentally.