J-coupling

The phenomenon of spin-spin interaction mediated by covalent bonds (usually the nearest), which leads to splitting of spectral peaks. Also known as indirect or scalar coupling. The magnitude of the effect is given by the coupling constant, J, and molecules exhibiting this are subdivided into AX systems or AB systems.

See also TE averaging and COSY.

J-modulation

See echo modulation.

JET

Name given to Toshiba’s radial k-space technique for motion compensation.

Joule

The unit of energy. It is defined as the energy exerted by a force of 1 N in order to move an object 1 m or 1 W of power for 1 s.