Two-dimensional NMR spectroscopy

Lesson
Tools

Introduction
- Introduction
- Background
- The experiment
  - Introduction
  - The alpha impulsion angle and the position of the M vector in a rotating coordinate system
  - The signal or F.I.D.
  - The notion of phase cycle
- The F.I.D.
Guidline for the two dimensional NMR spectroscopy
The role of the 2D NMR pulse sequences
Virtual NMR Spectrometer

The alpha impulsion angle and the position of the M vector in a rotating coordinate system

Impulsion angle du vecteur M (Fig 5) and position of the M vector (Fig. 5) is given by the following relation with B₁ which represents the amplitude or the power of the impulsion and t_p the width or duration of the impulsion. It is possible to make these two values vary together in such a way that particularly interesting rotation angles appear. One of these is the angle =90°.

In this case all the magnetization is orientated in the plane xy and the signal reaches its maximum of intensity^[1].

Fig. 5 : Location of the M vector after an impulsion time allowing an alpha angle of 90°

An other angle allows the inversion of the M vector by the application of an impulsion or = 180°

In this experiment, the vector M is orientated in –z. Practically, one uses the angle = 45° in order to get a good compromise between measurement time/quality of the response.

D.L. Rabenteck
Sensitivity enhancement by signal averaging in pulsed by Fourier transform NMR spectroscopy ; J. of Chem. Ed. Vol. 61, n°70, Oct 1984

Homepage