Line-narrowing by polychromatic selective spin-locking in NMR

Selective Spin-Locking (SSL) of the magnetisation vectors of selected singlets or multiplets in high-resolution Nuclear Magnetic Resonance (NMR) spectra by mono- or polychromatic selective radio-frequency (RF) irradiation can reduce the line-widths to the limit given by homogeneous T 1 ρ relaxation. The resulting line-narrowing leads to an increase in signal height of spectra of 1 H, 19 F, 31 P or other nuclei that is in principle only limited by the ratio T 1 ρ / T 2 *. At the same time, the scalar interactions that give rise to multiplets are decoupled, thus leading to an additional gain in signal height. The amplification factors allow one to use samples at low concentrations. Common one-dimensional (1D) experiments such as inversion recovery (IR) as well as the excitation and reconversion of Long-Lived States (LLS) by Spin-Lock Induced Crossing (SLIC) can significantly benefit from SSL.