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 ω 2 dimension with a sideband pattern in ω 1 in which the intensities mimic those for a sample spinning at a fraction of the rate ω r/ N. Advantages of the experiment include the use of standard methods to extract the principal tensor components from the ω 1 sideband patterns and the small number of t 1 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 t 1. Amplification factors up to 32 are demonstrated experimentally.