Gradient enhanced NMR is a method for obtaining high resolution nuclear magnetic resonance spectra without the need for ''phase cycling''.

Gradient In vector calculus, the gradient of a scalar-valued differentiable function of several variables is the vector field (or vector-valued function) \nabla f whose value at a point p is the "direction and rate of fastest increase". If the gradi ...

methodology is used extensively for two purposes, either rephasing (selection) or

dephasing In physics, dephasing is a mechanism that recovers classical behaviour from a quantum system. It refers to the ways in which coherence caused by perturbation decays over time, and the system returns to the state before perturbation. It is an im ...

(elimination) of a particular magnetization transfer pathway. It includes the application of

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

gradient pulses to select specific

coherence Coherence, coherency, or coherent may refer to the following: Physics * Coherence (physics), an ideal property of waves that enables stationary (i.e. temporally and spatially constant) interference * Coherence (units of measurement), a deriv ...

s. By using actively shielded gradients, a gradient pulse is applied during the evolution period of the selected coherence to dephase the transverse

magnetization In classical electromagnetism, magnetization is the vector field that expresses the density of permanent or induced magnetic dipole moments in a magnetic material. Movement within this field is described by direction and is either Axial or Di ...

and another gradient pulse refocuses the desired coherences remaining during the acquisition period.

Advantages

*Significant reduction in measuring time *Reduced T1 artifacts *Elimination of phase cycling and difference methods *Possibility for three and four-

quantum editing In physics, a quantum (plural quanta) is the minimum amount of any physical entity (physical property) involved in an interaction. The fundamental notion that a physical property can be "quantized" is referred to as "the hypothesis of quantizati ...

*The ability to detect resonances at the same chemical shift as a strong solvent

resonance Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillatin ...

Drawbacks

*A need for field-frequency-lock blanking during long runs.

Examples

*Selection of transverse magnetization (I_x, S_x, I_y etc.): (+)gradient 180°(x) (+)gradient *Suppression of transverse magnetization (I_x, S_x, I_y etc.): (+)gradient 180°(x) (-)gradient

References

*Ralph E. Hurd, Gradient-Enhanced Spectroscopy, Journal of magnetic resonance. 87, 422-428 (1990)
Nuclear magnetic resonance