INEPT

INEPT (Insensitive Nuclei Enhanced by Polarisation Transfer) is used in many pulse sequences utilising the high relative sensitivity of the ¹H nuclei (I) and transferring polarisation to insensitive nuclei (S) such as ¹³C and ¹⁵N.

A 90° (^π/₂) pulse on I creates transverse magnetisation (-I_Y).

Simultaneous 180° (π) pulses on I and S at the centre of two identical delays (τ=1/4*¹J_IS) allows the evolution of heteronuclear coupling and refocuses chemical shift. At the end of this spin echo antiphase I magnetisation with respect to S is achieved (2I_XS_Z).

Simultaneous 90° pulses on I and X transfer polarisation resulting in antiphase S magnetisation with respect to I (2I_ZS_Y).