10 - F1 and F2 offsets

To extract the quadrupole product parameter

and the true isotropic chemical from a pure 2D MQMAS spectrum, we need to scale the F1 axis. Since several conventions for scaling this axis appear in the literature, we have to take care of the values of several parameters.

We recall the 2D Data Parameters form by selecting the menu items:

Acquire/2D Data Parameters

First dimension F1

Three parameters should be fixed properly for the first dimension:

• the dwell time a,
• the spectrometer frequency b,
• and the frequency offset c.

We recommend our review article about scaling the F1 axis for setting these three parameters.

Second dimension F2

The F2 offset or the frequency offset of the second dimension is:

d = O1 - SR

where the spectrum reference SR and the spectrometer frequency offset O1 are provided by Bruker spectrometers. The value of d is the same whatever the convention used for scaling the F1 axis.