Cross-polarization
Cross-polarization (CP), originally published in 1962 as nuclear double resonance in the rotating frame by Sven R. Hartmann and Erwin Hahn is a solid-state nuclear magnetic resonance (ssNMR) technique used to transfer nuclear magnetization from different types of nuclei via heteronuclear dipolar interactions. The 1H-X cross-polarization dramatically improves the sensitivity of ssNMR experiments of most experiments involving spin-1/2 nuclei, capitalizing on the higher 1H polarization, and shorter T1(1H) relaxation times.